- CO activation pathways and the mechanism of Fischer-Tropsch synthesis
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Unresolved mechanistic details of monomer formation in Fischer-Tropsch synthesis (FTS) and of its oxygen rejection routes are addressed here by combining kinetic and theoretical analyses of elementary steps on representative Fe and Co surfaces saturated w
- Ojeda, Manuel,Nabar, Rahul,Nilekar, Anand U.,Ishikawa, Akio,Mavrikakis, Manos,Iglesia, Enrique
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- Reactivity of Silanes with (tBuPONOP)Ruthenium Dichloride: Facile Synthesis of Chloro-Silyl Ruthenium Compounds and Formic Acid Decomposition
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The coordination of tBuPONOP (tBuPONOP=2,6-bis(ditert-butylphosphinito)pyridine) to different ruthenium starting materials, to generate (tBuPONOP)RuCl2, was investigated. The resultant (tBuPONOP)RuCl
- Anderson, Nickolas H.,Boncella, James M.,Tondreau, Aaron M.
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- Photocatalytic reactions under irradiation of visible light over gold nanoparticles supported on titanium(IV) oxide powder prepared by using a multi-step photodeposition method
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Titanium(IV) oxide (TiO2) having both smaller and larger gold (Au) particles was successfully prepared by a multi-step (MS) photodeposition method. When 0.25 wt% Au loading per photodeposition was repeated four times, smaller and larger Au particles having average diameters of 1.4 and 13 nm, respectively, were fixed on TiO2, and the Au/TiO2 sample exhibited strong photoabsorption around 550 nm due to surface plasmon resonance (SPR) of the larger Au particles. Various Au/TiO2 samples were prepared by changing the Au loading per photodeposition and the number of photodepositions. Effects of the conditions in MS photodeposition and sample calcination on Au particle distribution and photoabsorption properties were investigated. These samples were used for hydrogen (H2) formation from 2-propanol and mineralization of acetic acid in aqueous suspensions under irradiation of visible light. In the case of H2 formation under deaerated conditions, the reaction rate of Au/TiO2 having both larger and smaller particles was 4 times higher than that of the Au/TiO2 sample without smaller Au particles, indicating that smaller Au particles acted effectively as a co-catalyst, that is, as reduction sites for H2 evolution. On the other hand, in the case of mineralization of acetic acid under aerated conditions, carbon dioxide formation rates were independent of the presence of smaller Au particles, indicating that the smaller Au particles had little effect on the mineralization of acetic acid. To extend the possibility of Au/TiO2 for H2 formation under irradiation of visible light, H2 formation from ammonia (NH3) as biomass waste was examined under deaerated conditions; NH3 was decomposed to H 2 and nitrogen with a stoichiometric ratio of 3:1. The Royal Society of Chemistry 2014.
- Tanaka, Atsuhiro,Sakaguchi, Satoshi,Hashimoto, Keiji,Kominami, Hiroshi
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- Study on the kinetics of thermal decomposition of CaCO3
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By means of TG, the thermal decomposition of the powdered CaCO3 was tested with its various dispersities, range of size, and the different content of CO2 in flowing nitrogen. Formulae for calculating the rate and time of decomposition were obtained.
- Wei,Luo
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- Autothermal reforming of CH4 over supported Ni catalysts prepared from Mg-Al hydrotalcite-like anionic clay
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spc-Ni/MgAl (spc: solid-phase crystallization method) catalysts were prepared from Mg-Al hydrotalcite-like compounds containing Ni at the Mg site as the precursors and tested for partial oxidation of CH4 into synthesis gas. The activity of spc-
- Takehira, Katsuomi,Shishido, Tetsuya,Wang, Peng,Kosaka, Tokuhisa,Takaki, Ken
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- Synthesis of four-angle star-like CoAl-MMO/BiVO4 p-n heterojunction and its application in photocatalytic desulfurization
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A four-angle star-like Co-Al mixed metal oxide (CoAl-MMO)/BiVO4 heterojunction has been synthesized via a hydrothermal method and following sintering. The CoAl-MMO/BiVO4 is derived from CoAl-LDHs/BiVO4, in which CoAl-LDHs leads to a distribution of amorphous CoAl-MMO. The CoAl-MMO loading on BiVO4 greatly enhances visible light absorption, improves charge separation by band offset charge transfer, and makes flat band potential more negative. The three effects together result in excellent photocatalytic activity. Under visible light irradiation, desulfurization efficiency of thiophene has achieved up to 98.58% on CoAl-MMO/BiVO4 with molar ratio of 0.3:5.
- Yun, Limin,Yang, Zhanxu,Yu, Zong-Bao,Cai, Tianfeng,Li, Yue,Guo, Changyou,Qi, Chengyuan,Ren, Tieqiang
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- Structure of surface tantalate species and photo-oxidation of carbon monoxide over silica-supported tantalum oxide
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Tantalum oxide (10 wt.% as Ta2O5) supported on silica was prepared and the structure and the photo-oxidation of carbon monoxide over the catalyst sample were investigated. XAFS analysis showed that surface tantalate is a TaO4 tetrahedral species with a Ta=O bond which is a photoactive center. The initiation of the photo-oxidation of carbon monoxide is the photoadsorption of an oxygen molecule on the catalyst sample, elucidated by photoluminescence. EPR spectroscopy showed that the photo-excited center interacts with an oxygen molecule to form a T-type ozonide ion. A carbon monoxide ion attacks the ozonide ion to form an [O3-CO]- paramagnetic intermediate to lead the production of carbon dioxide.
- Tanaka, Tsunehiro,Nojima, Hiroyuki,Yamamoto, Takashi,Takenaka, Sakae,Funabiki, Takuzo,Yoshida, Satohiro
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- Catalytic properties of γ-Al2O3 supported Pt-FeOx catalysts for complete oxidation of formaldehyde at ambient temperature
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A series of γ-Al2O3 supported Pt-FeOx catalysts (Pt-FeOx/Al2O3) with different Fe/Pt atom ratios were prepared, and their catalytic properties were investigated in the oxidation of formaldehyde. It was found that the catalytic activities of Pt-FeOx/Al2O3 catalysts are varied with the change of Fe/Pt ratios. Among them, the sample with a Fe/Pt ratio of 1.0 exhibits the highest activity, which can efficiently convert formaldehyde to CO2 at ambient temperature. The catalytic activity of the Pt-FeOx/Al2O3 catalyst can be further improved by the addition of water vapor into the feed stream. A variety of characterization results showed that both Pt nanoparticles and FeOx species are highly dispersed on the surface of the γ-Al2O3 support. Changing Fe/Pt ratios could influence the chemical states and the redox properties of Pt and Fe species. The catalysts with appropriate Fe/Pt ratios have more accessible active sites, i.e., the Pt-O-Fe species, which are located at the boundaries between FeOx and Pt nanoparticles, thus showing high activity for the oxidation of formaldehyde under ambient conditions.
- Cui, Weiyi,Yuan, Xiaoling,Wu, Ping,Zheng, Bin,Zhang, Wenxiang,Jia, Mingjun
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p. 104330 - 104336
(2015)
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- Purification and characterization of urease from dehusked pigeonpea (Cajanus cajan L) seeds.
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Urease has been purified from the dehusked seeds of pigeonpea (Cajanus cajan L.) to apparent electrophoretic homogeneity with approximately 200 fold purification, with a specific activity of 6.24 x10(3) U mg(-1) protein. The enzyme was purified by the sequence of steps, namely, first acetone fractionation, acid step, a second acetone fractionation followed by gel filtration and anion-exchange chromatographies. Single band was observed in both native- and SDS-PAGE. The molecular mass estimated for the native enzyme was 540 kDa whereas subunit values of 90 kDa were determined. Hence, urease is a hexamer of identical subunits. Nickel was observed in the purified enzyme from atomic absorption spectroscopy with approximately 2 nickel ions per enzyme subunit. Both jack bean and soybean ureases are serologically related to pigeonpea urease. The amino acid composition of pigeonpea urease shows high acidic amino acid content. The N-terminal sequence of pigeonpea urease, determined up to the 20th residue, was homologous to that of jack bean and soybean seed ureases. The optimum pH was 7.3 in the pH range 5.0-8.5. Pigeonpea urease shows K(m) for urea of 3.0+/-0.2 mM in 0.05 M Tris-acetate buffer, pH 7.3, at 37 degrees C. The turnover number, k(cat), was observed to be 6.2 x 10(4) s(-1) and k(cat)/K(m) was 2.1 x 10(7) M(-1) s(-1). Pigeonpea urease shows high specificity for its primary substrate urea.
- Das, Nilanjana,Kayastha, Arvind M,Srivastava, Punit K
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- The effect of the particle size on the kinetics of CO electrooxidation on high surface area Pt catalysts
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Using high-resolution transmission electron microscopy (TEM), infrared reflection-absorption spectroscopy (IRAS), and electrochemical (EC) measurements, platinum nanoparticles ranging in size from 1 to 30 nm are characterized and their catalytic activity for CO electrooxidation is evaluated. TEM analysis reveals that Pt crystallites are not perfect cubooctahedrons, and that large particles have rougher surfaces than small particles, which have some fairly smooth (111) facets. The importance of defect sites for the catalytic properties of nanoparticles is probed in IRAS experiments by monitoring how the vibrational frequencies of atop CO (νCO) as well as the concomitant development of dissolved CO 2 are affected by the number of defects on the Pt nanoparticles. It is found that defects play a significant role in CO clustering on nanoparticles, causing CO to decrease/increase in local coverage, which yields to anomalous redshift/ blueshift νCO frequency deviations from the normal Stark-tuning behavior. The observed deviations are accompanied by CO2 production, which increases by increasing the number of defects on the nanoparticles, that is, 1 ≤ 2 ad on defect sites rather than by CO energetics. These results are complemented by chronoamperometric and rotating disk electrode (RDE) data. In contrast to CO stripping experiments, we found that in the backsweep of CO bulk oxidation, the activity increases with decreasing particle size, that is, with increasing oxophilicity of the particles.
- Arenz, Matthias,Mayrhofer, Karl J. J.,Stamenkovic, Vojislav,Blizanac, Berislav B.,Tomoyuki, Tada,Ross, Phil N.,Markovic, Nenad M.
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- Catalytic low-temperature combustion of dichloromethane over V-Ni/TiO2 catalyst
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Vanadium-nickel mixed oxides supported on TiO2 (anatase) were prepared by wet impregnation using ammonium metavanadate and nickel nitrate aqueous solution. The performance of as-prepared samples in catalytic dichloromethane (DCM) combustion was investigated, and their physicochemical properties were characterized in detail by X-ray diffraction, N2 physisorption, H2 temperature-programmed reduction, NH3 temperature-programmed desorption, and Raman spectroscopy analyses. Results showed DCM combustion activity over V-Ni/TiO2 catalyst was superior to that of V2O5/TiO2 and NiO/TiO2 catalysts. DCM could be completely converted into CO2, HCl, and a little amount of CO over Ni-V/TiO2 catalyst at 350 °C, the toxic by-products, such as CH3Cl, aldehydes and phosgene could not be observed by online IR spectroscopy. The high catalytic activity, selectivity, and stability of V-Ni/TiO2 catalyst could be due to the good oxidative dehydrogenation ability (ODH), the good reducibility of active oxygen species, and suitable strength of Lewis acidic sites upon introduction of nickel oxide.
- Zhang, Xinhua,Pei, Zhiying,Ning, Xingjie,Lu, Hanfeng,Huang, Haifeng
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- Low temperature synthesis of tungsten trioxide/bismuth tungstate heterojunction with enhanced photocatalytic activity
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In this paper, the heterostructure composed of tungsten trioxide (WO3) and bismuth tungstate (Bi2WO6) was synthesized by a hydrothermal treatment at low temperature of 95°C. The orthorhombic Bi2WO6 was formed on the surface of WO3 through a substitution of H2O molecules with [Bi2O2]2+ during the hydrothermal process. The transmission electron microscopy (TEM) revealed that an intimate interface was observed between the heterojunction of WO3 and Bi2WO6. The WO3/Bi2WO6 showed more UV-visible light absorption and higher photocatalytic performance compared with pure WO3 and Bi2WO6. The efficient separation of electron-hole pairs because of the special structure and spectral property of the WO3/Bi2 WO6 heterojunction might account for the enhanced photocatalytic activity.
- Wang, Yue,Liu, Yan-Jun,Li, Shao-Yang,Ye, Mao,Shao, Yin-Hua,Wang, Rong,Guo, Li-Feng,Zhao, Cui-E,Wei, Ang
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- Polyethylene glycol-doped BiZn2VO6 as a high-efficiency solar-light-activated photocatalyst with substantial durability toward photodegradation of organic contaminations
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In this study, we focus on a simple, low-priced, and mild condition hydrothermal route to construct BiZn2VO6 nanocompounds (NCs) as a novel photocatalyst with strong solar light absorption ability for environmental purification using solar energy. NCs were further doped with polyethylene glycol (PEG) to improve their photocatalytic efficiency for photodegradation processes through inhibition of fast charge carrier recombination rates and higher charge separation efficiency. Surface morphology, phase structure, optical characteristics, and band structure of the as-prepared samples were analyzed using XRD, EDX, XPS, SEM, UV-vis spectroscopy, CL, and BET techniques. PEG-doped BiZn2VO6 NCs were applied as effective materials to degrade various kinds of organic pollutants including cationic and anionic types, and these NCs exhibited excellent photocatalytic efficiency as compared to traditional photocatalysts. In particular, the PEG-doped BiZn2VO6 (0.10% w/v) photocatalyst exhibited highly enhanced photocatalytic performance with improvements of about 46.4, 28.3, and 7.23 folds compared with PEG-doped ZnO nanorods (NRs), pristine BiVO4, and BiZn2VO6 samples, respectively, for the decomposition of congo red (CR) dye. After 40 minutes of sunlight irradiation, 97.4% of CR was decomposed. In this study, scavenging experiments indicated that both hydroxyl radicals and holes play dominant roles in CR photodegradation under simulated solar light irradiation. Meanwhile, the optimal photocatalyst demonstrated good reproducibility and stability for successive cycles of photocatalysis.
- Pirhashemi, Mahsa,Elhag, Sami,Habibi-Yangjeh, Aziz,Pozina, Galia,Willander, Magnus,Nur, Omer
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- Regulation of mixed Ag valence state by non-thermal plasma for complete oxidation of formaldehyde
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Formaldehyde is an important air pollutant and its removal is essential to protect human health and meet environmental regulations. Ag-based catalyst has a considerable potential for HCHO oxidation in low temperature range. The valence state of Ag is one of the key roles in formaldehyde catalytic oxidation. However, its effect on activity is still ambiguous. Non-thermal plasma and conventional calcination were employed to regulate Ag valence state in this study. Three Ag-Co/CeO2 catalysts with totally different distribution of Ag species were obtained. A special mixed Ag valence state, ~50% Agδ+ with a few Ag0 and Ag+, was achieved by plasma activation. It had the merits of both good activity and stability. A close relationship between Ag valence state and the activity for HCHO oxidation was established. The activity of different Ag species follows the order: Agδ+ + Ag0 + Ag+ > Agδ+ > Ag0 > Ag+.
- Gan, Yanling,Huang, Haibao,Ji, Jian,Li, Kai
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- Highly efficient Pd-ZnO catalyst doubly promoted by CNTs and Sc 2O3 for methanol steam reforming
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A type of Pd-ZnO catalyst doubly promoted by CNTs and Sc2O 3 for methanol steam reforming (MSR) was developed, and displayed excellent activity and operation stability for the selective formation of H 2 and CO2. Over a Pd0.15Zn1Sc 0.067-10%CNTs catalyst under the reaction conditions of 0.5 MPa and 548 K, the STY(H2) can maintain stable at the level of 1.56 mol h-1 g-1 at 75 h after the reaction started, which was 1.7 times that of the corresponding (CNTs and Sc)-free counterpart Pd 0.15Zn1. Characterization of the catalyst revealed that the highly conductive CNTs could promote hydrogen spillover from the PdZn/ZnO-sites to the CNTs adsorption-sites, and then combine to form H 2(a), followed by desorbing to H2(g), which would help increase the rate of a series of surface dehydrogenation reactions in the MSR process. The pronounced modification action of Sc3+ may be due to the high solubility of Sc2O3 in ZnO lattice. Solution of a small amount of Sc2O3 in ZnO lattice resulted in the formation of Schottky defects in the form of cationic vacancies at the surface of ZnO, where the (PdZn)0-Pd2+ clusters can be better stabilized through the Pd2+ accommodated at the surface vacant cation-sites. This would be conducive to inhibiting the sintering of the catalytically active (PdZn)0 nanoparticles, and thus, markedly prolonging the life of the catalyst.
- Yang, Lu,Lin, Guo-Dong,Zhang, Hong-Bin
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- Boosting molecular oxygen activation of SrTiO3 by engineering exposed facets for highly efficient photocatalytic oxidation
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Engineering exposed facets for improving the activation of molecular oxygen into O2- species and charge separation is a promising way to improve photocatalytic oxidation activity. Herein, SrTiO3 nanocrystals with controllably exposed {001} and {110} facets are prepared as a proof-of-concept candidate to study the effect of exposed facets on the activation of molecular oxygen into O2- species, finally acting on the photocatalytic oxidation of gaseous HCHO. The photocatalytic test demonstrates that {110} facet exposed SrTiO3 nanoparticles present a HCHO photocatalytic degradation rate about 6.8 times faster than that of the {001} facet exposed one. The experiments and theoretical calculations together confirm that as compared to the {001} facet exposed sample, the {110} facet exposed sample is favorable for activating molecular oxygen to produce O2- species under the irradiation of light, owing to the relatively higher conduction band position and lower surface adsorption energy for O2 molecules as well as advantageous charge accumulation on adsorbed O2 molecules. Finally, the new production of O2- species and the higher charge separation contribute to the superior HCHO photocatalytic oxidation activity of {110} facet exposed SrTiO3. This interesting finding is probably useful for the design of highly efficient single crystal photocatalysts for photocatalytic oxidation reactions.
- Wu, Xiaoyong,Wang, Xiaoyang,Li, Jun,Zhang, Gaoke
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- VOx-Pt/Al2O3 catalysts for hydrogen production
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Platinum supported catalysts are promising systems to a wide range of catalytic reactions involved in the hydrogen production chain. The performance of these catalysts can be enhanced by designing properly their nature, composition and structure. In this context, the addition of a second metal oxide on a catalyst composed of a well dispersed Pt phase over a high surface area support may be a powerful strategy. In this work we impregnated VOx species over Pt/Al2O3 and evaluated the catalysts performance for water-gas shift (WGS) and glycerol steam reforming (GSR) reactions. The catalysts characterization showed that VOx species formed over the Pt/Al2O3 surface were not deeply affected by the loading in the range of 0.5–2.0?V atoms per nm2 and were reduced at mild temperatures. In situ measurements during catalysts activation and WGS reaction showed that VOx species presented mixed valence (V3+/V4+) while Pt was in metallic state. The addition of vanadium increased Pt/Al2O3 WGS activity; however, the improvement did not linearly correlate with the loading. Under GSR, the results indicated that the WGS step was favored by the presence of vanadium but the selectivity to H2 decreased, which could be attributed to the parallel reactions enhanced by the acidic nature of the VOx sites.
- Kokumai, Tathiana M.,Cantane, Daniel A.,Melo, Guilherme T.,Paulucci, Luigi B.,Zanchet, Daniela
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- Enhanced performance of chemical looping combustion of methane with Fe2O3/Al2O3/TiO2 oxygen carrier
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Iron-based oxygen carriers supported on alumina or alumina/titania were prepared and evaluated for chemical looping combustion of methane. The reduction conversion of Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 particles was markedly increased with increasing inlet concentration and was slightly enhanced by elevated operating temperatures. According to the shrinking core model, the mass transfer coefficients (kg) of Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 reduction with methane are found to be 0.07 and 0.12?mm s?1. Complete combustion of methane is almost achieved for experiments conducted with Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 operated as the Fe2O3/CH4 molar ratio reached about 5.4 and 4.4, respectively. Carbon deposition during methane combustion was avoided by using Fe2O3/Al2O3/TiO2 as an oxygen carrier. More heat was generated for the combustion of methane by Fe2O3/Al2O3/TiO2 oxygen carriers because methane more fully reacted with the Fe2O3 contained in the Fe2O3/Al2O3/TiO2 oxygen carriers.
- Wu, Hsuan-Chih,Ku, Young
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- Selective oxidation of CO in the presence of H2, H2O and CO2 via gold for use in fuel cells
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An Au/Fe2O3 catalyst prepared using a two-stage calcination procedure achieves target conversion and selectivity for the competitive oxidation of dilute CO in the presence of moist excess H2 and CO2. The Royal Society of Chemistry 2005.
- Landon, Philip,Ferguson, Jonathan,Solsona, Benjamin E.,Garcia, Tomas,Carley, Albert F.,Herzing, Andrew A.,Kiely, Christopher J.,Golunski, Stanislaw E.,Hutchings, Graham J.
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- Correlation between the Pt2+/Pt4+ ratio and the catalytic activity for the CO oxidation of Ba12[BaxPt3-x]Pt6O27 (0 ≤ x ≤ 3)
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A variety of perovskite-type mixed oxides corresponding to the solid solution Ba12[BaxPt3-x]Pt6O27 (0 ≤ x ≤ 3) was studied by X-ray photoelectron spectroscopy (XPS). Pt was found to be in two valence states, Pt2+ and Pt4+, and the quantity of Pt2+ decreases when x increases. The intrinsic activity, for catalytic CO oxidation, was found to be dependent on x. At low temperature (below 170°C), the highest activity is obtained for Ba12Pt9O27 (x = 0) and the activity decreased with increasing x. The apparent activation energies increased, from 80 to 110 kJ·mol-1, when x increased; for a sample of metallic platinum catalyst studied in the same conditions, a value of 120 kJ·mol-1 was found. The partial reaction order/O2 (in the range of 0.64 to 0.90) increased with x while the partial order/CO (in the range of -0.34 to -0.70) decreased when x increased. Moreover, for the oxide containing only Pt4+ (Ba15Pt6O27) the reaction orders were similar to those determined for the metallic platinum. Hence, there is undoubtedly a correlation between the Pt2+/Pt4+ ratio in these oxides and the catalytic activity for CO oxidation. This can be explained by assuming that CO chemisorption on Pt2+ is weaker than on Pt4+, which implies a less inhibitor effect of CO at low temperature.
- Grasset,Alphonse,Labrugere,Darriet,Rousset
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- Photocatalytic degradation of acetic acid in the presence of visible light-active TiO2-reduced graphene oxide photocatalysts
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Visible light-active TiO2–reduced graphene oxide photocatalysts were prepared using simple mechanical mixing of titanium dioxide with different amounts of rGO (0.1, 0.5, 1.0 and 2.0?wt.%) in the presence of 1-butyl alcohol. Structures and morphologies of the samples were examined by means of FTIR/DRS, UV–vis/DR, XRD, SEM, TEM and Raman spectroscopy. The photocatalytic properties were checked on the basis of acetic acid photooxidation (the steady rate of linear increase of the CO2 yield was used for the estimation of photocatalytic activity). The maximum photodegradation rate was observed for TiO2 decorated with 0.5 wt.% of rGO. The enhancement of photodegradation efficiency should be related to π-conjugation system, two-dimensional planar structure and efficient charge separation of reduced graphene oxide nanosheets.
- Morawski,Kusiak-Nejman,Wanag,Kapica-Kozar,Wróbel,Ohtani,Aksienionek,Lipińska
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- Catalytic Decomposition of CFC-112 and CFC-113 in the Presence of Ethanol
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Iron (III) chloride supported on activated charcoal was extremely effective for decomposition of CFC-112 and CFC-113 into CO and CO2 in the presence of ethanol at the low temperature.
- Miyatani, Daisaku,Shinoda, Kiyonori,Nakamura, Tadashi,Ohta, Minoru,Yasuda, Kensei
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- Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4
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Abstract Palladium loaded AlPO4 catalysts were synthesised and characterised by XRD, IR, UV-vis spectroscopy, temperature programmed desorption (TPD) and temperature programmed surface reaction (TPSR). The Pd2+ ions of the dispersed palladium on the amorphous surface of AlPO4 are in D4h symmetry. They can partially be reduced into Pd0 even in dynamic conditions by a mixture of butan-2-ol and oxygen. TPD/TPSR showed that the active sites are formed by the couple PdO/Pd. The presence of PdO on the surface favours the production of methyl ethyl ketone (MEK). The CO2 formation was never observed below 100 °C. Moreover, desorption of the MEK takes place in two waves arising from two different types of sites. Only the reactivity of the first set of sites which are located around 80 °C was considered in the present study. As a matter of fact, the oxidation of butan-2-ol into MEK (one) appear around 85 °C and stop before 100 °C. Oscillations of the temperature of the catalyst bed were also recorded but their amplitude never exceeds 7 °C. An oscillatory regime appears also for butan-2-ol pressures ranging from 0.61 to 1.65 kPa and for a total flow rate between 80 and 260 mL min-1. The oscillating oxidation of butan-2-ol is accompanied by a significant enhancement of the methyl ethyl ketone production.
- Ouariach, Omar,Kacimi, Mohamed,Ziyad, Mahfoud
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- Infrared chemiluminescence study of CO2 Formation in CO + NO reaction on Pd(110) and Pd(111) surfaces
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Infrared (IR) chemiluminescence studies of CO2 formed during steady-state CO + NO reaction over Pd(110) and Pd(111) surfaces were carried out. Kinetics of the CO + NO reaction were studied over Pd(110) using a molecular-beam reaction system in the pressure range of 10-2-10 -1 Torr. The activity of the CO + NO reaction on Pd(110) was much higher than that of Pd(111), which was quite different from the result of other experiments under a higher pressure range. On the basis of the experimental data on the dependence of the reaction rate on CO and NO pressures and the reaction rate constants obtained by using a reaction model, the coverage of NO, CO, N, and O was calculated under various flux conditions. From the analysis of IR emission spectra in the CO + O2 reaction on Pd(110) and Pd(111), the antisymmetric vibrational temperature (TVAS) was seen to be higher than the bending vibrational temperature (TVB) on Pd(110). In contrast, TVB was higher than T VAS on Pd(111). These behaviors suggest that the activated complex for CO2 formation is more bent on Pd(111) than that on Pd(110), which is reflected by the surface structure. Both TV B and TVAS for the CO + O2 reaction on Pd(110) and Pd(111) increased gradually with increasing surface temperature (TS). On the other hand, in the case of the CO + NO reaction on Pd(110) and Pd(111), TVAS decreased and TV B increased significantly with increasing TS. T VB was lower than TVAS at lower TS, while TVB was higher than T VAS at higher TS. Comparison of the data obtained for the two reactions indicates that TVB in the CO + NO reaction on Pd(110) at TS = 800 and 850 K is much higher than that in the CO + O2 reaction on Pd(110). ? 2005 American Chemical Society.
- Nakao, Kenji,Ito, Shin-Ichi,Tomishige, Keiichi,Kunimori, Kimio
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- Catalytic reforming of oxygenated hydrocarbons for hydrogen with low levels of carbon monoxide
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Vaporization of water leads to low levels of CO: Now, it is possible to produce low-CO-containing, H2-rich streams by simple, aqueous-phase reforming of oxygenates. The schematic of ethylene glycol reforming on a Pt catalyst shows the composition of a gas bubble in the aqueous-phase reactor. Lowering the H2 and CO2 pressures, by increasing the water pressure, lowers the CO concentration in the product. WGS = water-gas shift.
- Davda, Rupali R.,Dumesic, James A.
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- Improving heterogeneous photo-Fenton catalytic degradation of toluene under visible light irradiation through Ba-doping in BiFeO3 nanoparticles
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In this study, we prepared Bi1-xBaxFeO3 MNPs (x?=?0.03, 0.08, 0.12) via a rapid sol gel procedure to improve heterogeneous photo-Fenton catalytic degradation of toluene under visible light irradiation. We found that Ba-substitution in BiFeO3 magnetic nanoparticles (BFO MNPs) can play an important role in improving the photo-Fenton catalytic degradation of toluene from aqueous solution. Increasing the Ba doping level up to 12%, greatly affect in iron redox cycling and oxygens vacancies as compared to pure BFO MNPs. The iron redox cycling and existence of oxygen on the surface of Ba doped BFO had been affected by the photo-Fenton process. The scavenger effect evident from the study results confirmed that the photo-Fenton catalytic degradation of toluene from aqueous solution was mainly controlled by the formation characteristics of hydroxyl radical ([rad]OH) and also partially by the formation of other active species such singlet oxygen (1O2). The proposed radical reaction mechanism was also discussed. The degradation of toluene was partial in the dark but almost complete under visible light irradiation by the photo-Fenton catalytic degradation reaction. Bi1-x Bax FeO3 (x?=?0.12) showed the highest photo-Fenton catalytic degradation efficiency with a toluene removal of 98%, total organic carbon (TOC) and chemical oxygen demand (COD) reduction of 85% and 94%, respectively, after 40?min of visible light irradiation.
- Soltani, Tayyebeh,Lee, Byeong-Kyu
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- Spectroscopy of Hydrothermal Reactions 13. Kinetics and Mechanisms of Decarboxylation of Acetic Acid Derivatives at 100-260 °C under 275 bar
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The rates and pathways of decarboxylation of acetic acid derivatives, RCO2H, and their Na+ salts, RCO2Na, which possess electron-withdrawing groups (R = CCl3-, CF3-, HOC(O)CH2-, NH2C(O)CH2-, CF3CH2-, NCCH2-, CH3C(O)-) were determined in H2O at 100-260 °C and a pressure of 275 bar. Simple conversion to RH + CO2 occurs in most cases, except that H2O appears to be a required reactant for the anions. Real-time FTIR spectroscopy was used to determine the rate of formation of CO2 in flow reactors constructed of 316 stainless steel (SS) and of titanium. With a few exceptions, the rate of decarboxylation is similar within the 95% confidence interval in 316 SS and Ti and the difference is smaller than that caused by R. Therefore, while wall effects/catalysis may exist in some cases, it plays a lesser role in the relative rates than the substituent R. The acid form of the keto derivatives decarboxylates more rapidly than the anionic form, whereas the reverse is true for the nonketo derivatives. In keeping with the greater role of H2O as a reactant, the entropy of activation for the anions is smaller or more negative than for the acids. A Taft plot of the decarboxylation rates suggests that the mechanistic details can be interpreted in terms of the various roles of R. Where R = HOC(O)CH2- and NH2C(O)CH2-, decarboxylation occurs faster than expected, probably because a cyclic transition state can exist. The rate is slower than expected for R = CF3-, perhaps because of stabilization of the acid by hyperconjugation. The mechanism of decarboxylation of acids of the remaining R groups is similar and the steric effect of R is somewhat more influential than its electron withdrawing power.
- Belsky,Maiella,Brill
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- Effect of pressure on the phase composition of Li(Na)/W/Mn/SiO2 composites and their catalytic activity for oxidative coupling of methane
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The phase state of Li/W/Mn/SiO2 and Na/W/Mn/SiO2 composites after exposure to high pressures (2.5 GPa at 500°C) and subsequent exploitation in oxidative coupling of methane (OCM) was studied. Comparison of the catalytic activity of the composites before and after exposure to high pressures indicates that the formation of Li(Na)/W/Mn/SiO2 composites catalytically active for OCM is significantly influenced by high pressures.
- Nipan,Artukh,Yusupov,Loktev,Spesivtsev,Dedov,Moiseev
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- Pronounced Synergetic Effect in the Catalytic Properties of LaMn(1-x)Cu(x)O3
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A pronounced synergetic effect has been found when LaMn(1-x)Cu(x)O3 (x=0.3-0.5) was prepared by a freeze-drying method from metal acetates of each component; LaMn0.6Cu0.4O3 showed much higher catalytic activity for the reactions of CO-O2 and NO-CO in comparison with LaMnO3 and La2CuO4.
- Mizuno, Noritaka,Fujiwara, Yoshiko,Misono, Makoto
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- Effects of Sodium Tetraborate as an Additive on the Reaction of α-Alumina with Sodium Carbonate
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Effects of sodium tetraborate as an additive in the reaction of α-alumina with molten sodium carbonate have been studied mainly in a N2 atmosphere.Addition of sodium tetraborate accelerates the reaction, the α-alumina reacted increasing from 31.7percent to 99.3percent by addition of sodium tetraborate corresponding to the initial B2O3/Na2O molar ratio of only 1/15 under the other same conditions.By means of the Jander equation the activation energy was found to be 53 kcal/mol for the α-Al2O3-Na2CO3-Na2B4O7 system, which was lower by 10 kcal/mol than that for the α-Al2O3-Na2CO3 system.X-Ray diffraction and thermal data were analyzed in relation to the phase equilibrium of the melt.
- Chang, Byong-Tae,Oh, Jae-Gun,Om, Suk-Ja
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- Solvothermal preparation of Ag nanoparticle and graphene co-loaded TiO2 for the photocatalytic degradation of paraoxon pesticide under visible light irradiation
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The growing use of organophosphorus compounds such as paraoxon as agriculture pesticides results in their accumulation in soils and groundwater. Therefore there is a high demand for developing efficient methods for removing these materials from contaminated environmental resources. In this study, Ag nanoparticle and graphene co-loaded TiO2 with various contents of Ag and graphene was prepared via a facile surfactant free solvothermal method in a mixture of water and ethanol solvents and was applied, for the first time, for the photocatalytic degradation of paraoxon (as a model organophosphorus compound) under visible light irradiation. In this ternary nanocomposite, the presence of Ag nanoparticles is for narrowing the band gap to the visible region due to its surface plasmon resonance (SPR) effect and the presence of graphene is for diminishing the recombination rate of the photogenerated electron and holes due to its high electrical conductivity. The results of photocatalytic activity tests demonstrate that the nanocomposite with 6% wt Ag and 1% wt graphene content has the best photocatalytic activity among the products. Investigation of the chemical state of the nanocomposites showed that the covering of Ag nanoparticle loaded TiO2 with a high weight ratio of graphene resulted in the formation of Ag-O bonds through bonding of Ag to the oxygen functional groups of graphene which causes a decrease of the SPR effect of Ag and by this way decreases the photocatalytic activity. Gas Chromatography-Mass Spectrometry (GC-MS) was used as analytical tool for determination of the photocatalytic reaction intermediates. GC-MS analysis results show that photodegradation of paraoxon produces 4-nitrophenol, di-ethylphosphate, mono-ethylphosphate, hydroquinone and hydroxyhydroquinone as major intermediates and subsequent photodegradation of these results in complete mineralization of paraoxon.
- Keihan, Amir Homayoun,Hosseinzadeh, Reza,Farhadian, Mousa,Kooshki, Hamid,Hosseinzadeh, Ghader
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- Partial oxidation of methane to synthesis gas: Novel catalysts based on neodymium–calcium cobaltate–nickelate complex oxides
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Novel catalysts based on neodymium–calcium cobaltate–nickelate complex oxides for the partial oxidation of methane to synthesis gas have been synthesized and studied using catalyst precursors with the general formula NdCaCo1–xNixOn (x = 0, 0.2, 0.4, 0.6, 0.8, 1) prepared by the solid state synthesis method. It has been shown that the synthesized samples form a series of solid solutions with a K2NiF4 structure at x ≤ 0.8 or a rhombically distorted K2NiF4 structure at x = 1. The products of conversion of the resulting precursors in a methane–oxygen mixture at high temperatures have shown high methane conversions and synthesis gas yields. The highest values of these parameters have been achieved in the presence of catalysts synthesized by the reduction of NdCaCo0.4Ni0.6On and NdCaNiOn precursors. The complete replacement of cobalt with nickel has led to an increase in the synthesis gas yield; however, it has been found that the resulting catalyst is prone to carbonization. It has been determined that an optimum nickel to cobalt ratio in the catalyst composition provides the formation of a carbonization-resistant catalyst.
- Dedov,Shlyakhtin,Loktev,Mazo,Malyshev,Tyumenova,Baranchikov,Moiseev
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- Highly-efficient steam reforming of methanol over copper modified molybdenum carbide
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Cu doped molybdenum carbide (Cu-MoxCy) catalysts were prepared by carburization of Cu doped molybdenum oxide (Cu-MoO3) using a temperature-programmed reaction with a 20% CH4-H2 mixture at 700 °C. Phas
- Ma, Yufei,Guan, Guoqing,Hao, Xiaogang,Zuo, Zhijun,Huang, Wei,Phanthong, Patchiya,Kusakabe, Katsuki,Abudula, Abuliti
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- Oxidative coupling of methane over Mn-Na2WO4 catalyst supported by monolithic SiO2
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In this work, oxidative coupling of methane was studied over monolithic Mn/Na2WO4/SiO2 catalysts. The monolithic catalysts were prepared by three different ways as (1) preparation of monolithic silica (monosil) followed by impregnation of Mn and Na2WO4 (2) preparation of monolithic silica with Mn addition during gelation (Mn-monosil) followed by impregnation of Na2WO4 and (3) preparation of monolithic silica as MCM-41 structure (MCM-monosil) followed by impregnation of Mn and Na2WO4. The catalysts were tested in a microflow reactor and the results were compared with those obtained over particulate catalysts. It was found that Mn-monosil performed best and produced C2 yield of 16.2%, which is close to the values obtained over particulate catalyst (19.3%). Mn-monosil was also passed the 10 h stability and hysteresis tests successfully. SEM characterization revealed that monolithic catalysts prepared by three different methods had different pore structure; it was also seen from SEM images that Mn-monosil preserved its original form better, and this was also verified by XRD analysis.
- Uzunoglu, Cagla,Leba, Aybuke,Yildirim, Ramazan
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- FOx News: Towards Methanol-driven Biocatalytic Oxyfunctionalisation Reactions
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The novel formate oxidase from Aspergillus oryzae (AoFOx) is a useful catalyst to promote H2O2-dependent oxyfunctionalisation reactions. In this contribution we exploit the substrate promiscuity of AoFOx to fully oxidise methanol and formaldehyde to CO2 and drive peroxygenase-catalysed stereoselective oxyfunctionalisation reactions. The highly atom efficient H2O2 generation system also enabled high catalytic turnover of the peroxygenase production enzyme.
- Willot, Sébastien J.-P.,Hoang, Manh Dat,Paul, Caroline E.,Alcalde, Miguel,Arends, Isabel W. C. E.,Bommarius, Andreas S.,Bommarius, Bettina,Hollmann, Frank
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- Growth of TiO2 nano-wall on activated carbon fibers for enhancing the photocatalytic oxidation of benzene in aqueous phase
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In the present study, TiO2 nano-wall networks (TNWs) were successfully grown on the surface of activated carbon fibers (ACFs) pre-coated with TiO2 nanoparticles (TNPs) via a hydrothermal process. The TNWs with an average length of 0.7–0.9 μm grew on the ACFs (ACF-TNW) surface in a three-dimensional direction to a complex structure with good uniformity and high crystallinity, as confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The maximum removal capacities of benzene in a combined process of photo-oxidation and sorption affinity were 111.6 and 144.8 mg/g for ACF-TiO2 and ACF-TNW, respectively, at pH 5, under UV light irradiation within 80 min. The highest benzene removal efficiency of 98.7% in the ACF-TNW system (in 100 mL of 50 mg/L), also confirmed by the CO2 emission results, was accompanied by total organic carbon (TOC) and chemical oxygen demand (COD) reductions of 79.5 and 82.3%, respectively. The ACF-TNW nanocomposite also showed a higher photocatalytic oxidation of benzene than that of TNPs due to the minimization of electron-hole recombination resulting from the transfer of photo-induced electrons through the ACFs surface. The ACF-TNW nanocomposite was also easily separated from aqueous solution for regeneration and showed good stability after multiple uses.
- Sharma, Ajit,Lee, Byeong-Kyu
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- Enhancement of the photocatalytic activity of a TiO2/carbon aerogel based on a hydrophilic secondary pore structure
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Improving the separation and utilization of electrons and holes in a photocatalytic process is a guarantee for high photocatalytic efficiency. We report a strategy to enhance the photocatalytic performance based on fabrication of a hydrophilic secondary pore structure by incorporating TiO2 into a porous carbon aerogel (CA) with a 9.3 nm pore diameter, where TiO2 resides on both the inner and outer surfaces of CA as evidenced by N2 sorption isotherms and transmission electron microscopy. In such a structure, the spatial separation efficiency of photoelectrons and photoholes is supposed to get enhanced with interface electrons transferring into the inner surface of the pores via conductive CA. As a result, HO formation can be promoted in the confined inter surface of the hydrophilic secondary channel through O2 reduction with the participation of photoelectrons and H2O. And the remaining photoholes on the outer surface can oxidize water to generate HO as well. In contrast, TiO2 is mainly dispersed on the outer surface of CA as small pore diameters of 3.4 and 4.3 nm; as a result, only uncombined photoholes on the outer surface contribute to HO generation via the water oxidation route. In line with this understanding, TiO2/CA (9.3 nm) shows the largest amount of HO and thereby the highest efficiency of dimethyl phthalate degradation, as respectively evidenced by the electron paramagnetic resonance spectroscopy and the photocatalytic degradation test. These findings unveil the contribution of the surface/interface synergy effect on the separation and utilization of electrons and holes in photocatalytic process, and provide a potential strategy to enhance the photocatalytic performance.
- Cui, Hua'Nan,Liang, Zhenxing,Zhang, Jinzhong,Liu, Hong,Shi, Jianying
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- Enhanced formic acid electro-oxidation on pdir nanoparticles prepared by ethylene glycol-assisted NaBH4 reduction process
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The carbon supported PdIr nanoparticles were synthesized by an ethylene glycol-assisted NaBH4 reduction method, and the mass ratio of Pd to Ir was optimized. Then, their performances for formic acid electro-oxidation (FAEO) were investigated. The XRD and
- Chen, Jinwei,Wang, Gang,Wang, Xueqin,Tian, Jing,Zhu, Shifu,Wang, Ruilin
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- Ethylenediamine-modulated synthesis of highly monodisperse copper sulfide microflowers with excellent photocatalytic performance
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Highly monodisperse CuS microflowers with uniform size and shape were successfully constructed by a simple one-pot solvothermal approach assisted by EDA and PVP. When used as photocatalysts, the as-obtained CuS materials exhibited excellent photocatalytic activity and good selectivity for the degradation of organic contamination in waters.
- Yang, Zheng Kun,Song, Le Xin,Teng, Yue,Xia, Juan
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- Toluene oxidation catalyzed by NiO/SiO2 and NiO/TiO2/SiO2: Towards development of humidity-resistant catalysts
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Toluene oxidation was catalyzed by NiO/SiO2 and NiO/TiO2/SiO2 under dry and highly humid (relative humidity = 70%) conditions at 250 and 350 °C. At 350 °C, both catalysts showed nearly complete removal of toluene and conversion of toluene to CO2 under humid as well as dry conditions. Catalytic activity of the NiO/SiO2 was significantly decreased by the increase in the humidity at 250 °C, whereas that of NiO/TiO2/SiO2 was much less sensitive to the humidity. A facile adsorption of water on NiO/SiO2 due to the hydrophilic nature of SiO2 surface resulted in a pronounced suppression of toluene adsorption on the surface and lower catalytic activity under humid conditions. On the contrary, a higher affinity of TiO2 towards toluene adsorption even under highly humid conditions can allow more humidity-independent catalytic activity of NiO/TiO2/SiO2. We suggest that the modulation of surface structure of supporting materials of nanoparticle catalysts can be useful for fabrication of more humidity-resistant heterogeneous catalysts.
- Park, Eun Ji,Lee, Ju Ha,Kim, Kwang-Dae,Kim, Dae Han,Jeong, Myung-Geun,Kim, Young Dok
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- Merits of photocatalytic and antimicrobial applications of gamma-irradiated Co: XNi1- xFe2O4/SiO2/TiO2; X = 0.9 nanocomposite for pyridine removal and pathogenic bacteria/fungi disinfection: Implication for wastewater treatment
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In this paper, we report a layer-by-layer approach for the preparation of a concentric recyclable composite (CoxNi1-xFe2O4/SiO2/TiO2; x = 0.9) designed for wastewater treatment. The prepared composite was investigated by X-ray diffraction spectroscopy, high-resolution transmission electron microscopy and scanning electron microscopy (SEM) supported with energy dispersive X-ray (EDX) spectroscopy to analyze crystallinity, average particle size, morphology and elemental composition, respectively. The antimicrobial activities of the prepared composite have been investigated against multi-drug-resistant bacteria and pathogenic fungi using a variety of experiments, such as zone of inhibition, minimum inhibitory concentration, biofilm formation and SEM with EDX analysis of the treated bacterial cells. In addition, the effects of gamma irradiation (with different doses) and UV irradiation on the antibacterial abilities of the prepared composite have been evaluated. Moreover, the effect of gamma irradiation on the crystallite size of the prepared composite has been studied under varying doses of radiation (25 kGy, 50 kGy and 100 kGy). Finally, the photocatalytic efficiency of the prepared composite was tested for halogen-lamp-assisted removal of pyridine (artificial wastewater). Various parameters affecting the efficiency of the photocatalytic degradation, such as photocatalyst dose, pyridine concentration, pH, point of zero charge and the presence of hydrogen peroxide, have been studied. Our results show that the synthesized composite has a well-crystallized semi-spherical morphology with an average particle size of 125.84 nm. In addition, it possesses a high degree of purity, as revealed by EDX elemental analysis. Interestingly, the prepared composite showed promising antibacterial abilities against almost all the tested pathogenic bacteria and unicellular fungi, and this was further improved after gamma and UV irradiation. Finally, the prepared composite was very efficient in the light-assisted degradation of pyridine and its degradation efficiency can be tuned based on various experimental parameters. This work provides a revolutionary nanomaterial-based solution for the global water shortage and water contamination by offering a new wastewater treatment technique that is recyclable, cost effective and has an acceptable time and quality of water.
- Abd Elkodous, M.,El-Batal, Ahmed I.,El-Khawaga, Ahmed M.,El-Sayyad, Gharieb S.,Elsayed, Mohamed A.,Gobara, Mohamed
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- Effects of la doping on structural, optical, electronic properties of Sr2Bi2O5 photocatalyst
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Single-phase Sr2Bi2O5 was obtained by calcination of the heterobimetallic complex precursor Sr[Bi(DTPA)]·9H2O (DTPA is diethylenetriaminepentaacetic acid) at 700 °C for 6 h. The effect of La doping on the crystal structure, surface area, morphology, surface chemical state, and absorption properties of Sr2Bi2O5 samples prepared from Sr[Bi(DTPA)]·9H2O were investigated. No traces of an impurity phase were detected in samples with a lower La content (3 and 5 mol%), while impurity phases such as Sr6Bi2O9 and SrCO3 were observed in Sr2Bi2O5 samples with larger La contents of 8 and 10 mol%. The Brunauer-Emmett-Teller surface area of Sr2Bi2O5 increased slightly with the content of La. High-resolution transmission electron microscopy revealed clear crystalline planes for both undoped and La-doped Sr2Bi2O5 samples without amorphous phases. Meanwhile, X-ray photoelectron spectroscopy indicated that the valence states of constituent metals were Sr2+, Bi3+, and La3+. The solubility limit of La in the Sr2Bi2O5 crystal phase was determined from Raman scattering measurements. La atoms substituted Bi sites when the doping content was low, while both Bi and Sr sites were substituted with La when the content of La was high. The electronic structure of Sr2Bi2O5 could be modified by La doping, resulting in a red shift of the absorption edge with increasing La content. The band-gap narrowing of Sr2Bi2O5 with La-doping was reproduced in energy-band calculations. The photocatalytic activity of Sr2Bi2O5 under visible-light irradiation for the oxidation of isopropanol was enhanced by doping with La.
- Obukuro, Yuki,Matsushima, Shigenori,Obata, Kenji,Suzuki, Takuya,Arai, Masao,Asato, Eiji,Okuyama, Yuji,Matsunaga, Naoki,Sakai, Go
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- Green Oxidative Degradation of Methyl Orange with Copper(II) Schiff Base Complexes as Photo-Fenton-Like Catalysts
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Two copper(II) complexes, namely [Cu(HL)Cl] (1) and [Cu(HL)Br] (2), where HL is the multidentate Schiff base N-[(2-oxy-acetate)benzyl]-2-aminothanol, were synthesized and fully characterized. The CuII ions in 1 and 2 are pentacoordinate and the
- Fei, Bao-Li,Yan, Qing-Ling,Wang, Jiang-Hong,Liu, Qing-Bo,Long, Jian-Ying,Li, Yang-Guang,Shao, Kui-Zhan,Su, Zhong-Min,Sun, Wei-Yin
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- Effects of metal promotion on the performance of CuZnAl catalysts for alcohol synthesis
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A series of CuZnAl catalysts modified with different promoters (Fe, Co, Ru, Zr, Mo, Mg, Mn, and Cr) have been prepared through co-precipitation, characterised by applying a combination of techniques, and tested for carbon monoxide hydrogenation. Cu reducibility in CuZnAl catalysts was affected by the addition of promoters. The ease of Cu reduction in the promoted catalysts leads to more active catalysts for the hydrogenation of carbon monoxide and the production of C2+ alcohols, whereas lower catalytic activity was observed over less reducible catalysts. The promotion of CuZnAl catalysts even with small amounts of Cr, Mn, and Fe resulted in a significant modification in the reaction selectivity. The Fe-containing catalyst demonstrated a dramatic increase in carbon monoxide conversion and C2+ alcohol productivity (30 mg g-1cath-1). Choose your alcohol wisely: The ease of Cu reduction in CuZnAl methanol synthesis catalysts promoted with metals leads to more active catalysts for the hydrogenation of carbon monoxide and the production of C2+ alcohols. The promotion of CuZnAl catalysts even with small amounts of Cr, Mn, and Fe results in a significant modification in the selectivity patterns.
- Beiramar, Jorge M.,Griboval-Constant, Anne,Khodakov, Andrei Y.
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- Enhancing the visible-light-induced photocatalytic activity of AgNbO3 by loading Ag@AgCl nanoparticles
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A new visible-light-driven plasmonic photocatalyst Ag@AgCl/AgNbO3 is prepared via loading with Ag@AgCl nanoparticles by an impregnating precipitation photoreduction method. The physical and chemical properties of catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and UV-Visible diffusion reflectance spectra. In comparison with pristine AgNbO3, Ag@AgCl/AgNbO3 exhibits a high visible-light-induced photocatalytic activity for degradation of methylene blue. Moreover, the photocatalytic mechanism is also discussed. The photoexcited electrons on the surface of the silver nanoparticles are injected due to surface plasmon resonance, and formed radical groups (O2-,·HOO, ·OH and Cl0), which enhanced the photocatalytic activity of Ag@AgCl/AgNbO3 in visible-light.
- Yang, Leifei,Liu, Junbo,Chang, Haibo,Tang, Shanshan
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- Effect of active and inert oxide on catalytic partial oxidation (CPO) of methane over supported Ni catalysts
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The effects of preparation method, types of carrier and different catalyst and support structures on the CH4 catalytic partial oxidation (CPO) activity of supported Ni catalysts are reviewed with respect to selected results obtained by this research group during the last five years. In particular, different preparation methods and structural effect of Ni supported on La2O3, on CeO2 and on mixed CeO2-La2O3 are discussed. The effects of the peculiarity of an active (redox) and of an inert oxide carrier, influencing the metal dispersion, the metal reducibility and the carbon formation, are considered by comparing the catalytic performance of nickel catalysts supported on CeO2 and on SiO2. Ni supported over a high surface area silica will be compared with a corresponding ceria-doped nickel catalyst. The results of a detailed material characterization attained by several techniques as XPS, XRD, TPR/TPO are described, aiming to elucidate the structure - activity relationship. The reviewing of the different case studies illustrates the importance of the interaction between support and active metals ultimately determining the surface distribution of the active sites and their final catalytic activity.
- LaParola, V.,Pantaleo, G.,Venezia, Anna
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- Rapid alloying of Au–Pd nanospheres by a facile pulsed laser technique: Insights into a molar-dependent electrocatalytic methanol oxidation reaction
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Direct methanol fuel cells have attracted extensive research interest because of their relatively high energy density and portability. It is important to rationally design the composition and surface atomic structure by efficient synthesis protocols to boost cell efficiency. In this study, we employed cohesive pulsed laser irradiation and ultrasonochemical techniques to synthesize and tune the molar ratio of an Au–Pd alloy for the methanol oxidation reaction (MOR). The effective implementation of extremely rapid photoinduced reduction and reaction conditions resulted in the formation of well-dispersed and homogenous nanospheres of the Au–Pd alloy with uniform particle size. Moreover, the composition-tuned Au–Pd alloy exhibited an improved electrocatalytic activity, which might be due to its improved electrical conductivity and higher CO tolerance. The alloy achieved relatively high mass and specific activities of 0.50 A/mgPd and 1.36 mA/cmPd2, respectively. Additionally, we studied the effect of the Au–Pd composition on the MOR activity and analyzed the reaction kinetics in depth. This work provides the foundation for implementing a laser-based technique to synthesize Pd-based alloy electrocatalysts for MOR application.
- Chinnadurai, Deviprasath,Choi, Myong Yong,Lee, Seung Jun,Lee, Young Wook,Yeon, Sanghun,Yu, Yiseul
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- Room temperature HCHO oxidation over the Pt/CeO2 catalysts with different oxygen mobilities by changing ceria shapes
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Oxygen mobility contributes to HCHO oxidation at room temperature. In this work, oxygen mobilities of the Pt/CeO2 catalysts were controlled by changing ceria shapes to nanorods (CeO2-R), nanocubes (CeO2-C) and nanoparticles (CeO2-P) for HCHO elimination. The smallest ceria crystallite size, the strongest metal-support interaction and the most oxygen vacancy in the Pt/CeO2-R catalyst than those in the Pt/CeO2-C and Pt/CeO2-P catalysts resulted in the greatest redox of surface lattice oxygen and the most oxygen molecules activation at oxygen vacancy sites. These contributed to the most active mobile oxygen and therefore the highest HCHO oxidation performance. In-situ diffused reflectance infrared Fourier-transform spectra (DRIFT) indicated the fastest decomposition of formate at Pt-CeO2 interface on the Pt/CeO2-R catalyst because of its highest oxygen mobility. This work illustrated importance of oxygen mobility for efficient HCHO oxidation.
- Wang, Fagen,Wang, Shuo,Wang, Yan
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- Heterogeneous photo-Fenton-like degradation of emerging pharmaceutical contaminants in wastewater using Cu-doped MgO nanoparticles
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A facile thermal decomposition method was utilized to synthesize mesoporous Cu-doped MgO nanoparticles. These Cu-MgO nanoparticles were shown to be efficient photo-Fenton-like catalysts for degrading emerging pharmaceutical contaminants in wastewater and completely oxidized salicylic acid within 1 h under optimized conditions. Tetracycline was shown to be converted to other intermediates with a large portion of it undergoing full mineralization. Batch experiments were conducted to demonstrate the effects of Cu loading on MgO, overall catalyst loading, and H2O2 concentration on the salicylic acid and tetracycline conversion and rate constants. Quenching experiments revealed that both ?OH radicals or HO2?/?O2- radicals were involved in the reaction, with the latter showing a higher contribution. The surface dissolution of MgO was shown to increase solution pH which completely prevented Cu from leaching out while retaining high activity. The catalyst reusability was shown to be satisfactory with high activity and conversion being preserved over five cycles.
- Baltrus, John P.,Baltrusaitis, Jonas,Knopf, Allan,Silva, Manoj,Williams, Clinton,Zhang, Lihua
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- Mesoporous Co3O4 with large specific surface area derived from MCM-48 for catalytic oxidation of toluene
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As one of the most promising candidates for the catalytic combustion of volatile organic compounds, crystalline cobalt oxide is one of the most used and cost-effective catalyst. We present here a mesoporous Co3O4 catalyst with large specific surface area of 182.5 ?m2/g derived from MCM-48 with a specific surface area of 1470.9 ?m2/g, giving the T90 (the temperature required for achieving a toluene conversion of 90%) of 229 ?°C and the apparent activation energy (Ea) of 17.53 ?kJ/mol for the oxidation of toluene, both of which are much lower than the Co3O4 catalysts prepared by using SBA-15 and MCM-41 as hard template (T90 ?~ ?260 ?°C, Ea ?~ ?30 ?kJ/mol). Constant complete conversion of toluene over M48-Co3O4 was observed for 60 ?h, suggesting its superior stability for toluene combustion. Characterization results indicated the large specific surface area, higher Co3+/Co2+ ratio as well as abundant surface-active oxygen exposed for easy accessibility of reactant molecules contribute simultaneously to the good catalytic oxidation performance of M48-Co3O4. Particularly, 400 ?°C was viewed to be the optimal calcination temperature for keeping the mesoporous structures of catalyst as much as possible. The reaction intermediates of toluene oxidation over M48-Co3O4 were detected based on both GC-MS and in-situ DRIFTS, demonstrating the formation of the benzyl alcohol, benzaldehyde, benzoic acid, itaconic anhydride and maleic anhydride, acetone, and acetic acid, etc., as the main intermediates.
- Gao, Wei,Tang, Xiaolong,Xie, Xizhou,Yi, Honghong,Yu, Qingjun,Zhang, Yuanyuan,Zhuang, Ruijie
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- In-situ preparation of Cu-BiOCl/Bi2O3-C-dots composite and excellent performance for photocatalytic bisphenol A degradation
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Economical elimination of organic pollutants from waste water has be paid more attention owing to its environmental and ecological significance. In this study, an easily achievable process to in-situ fabricate copper and co-modified Z-scheme BiOCl/Bi2O3 heterojunction was proposed. The study on the formation mechanism indicated that the introduction of copper ions is favorable for the formation of Bi-based catalyst with flaky morphology while the addition C-dots makes the nanosheets loosely be packed and intercrossed each other. The composite exhibited a high degradation efficiency for Bisphenol A (BPA) and 91% of BPA was removal within 35 min under xenon lamp irradiation. The excellent photocatalytic performance was attributed to the synergistic effect of the in-situ formation Z-scheme BiOCl/β-Bi2O3 heterojunction, multiple charge transfer channels including Cu2+/Cu+ and C-dots, and efficient charge separation. The electron paramagnetic resonance (EPR) analysis and quenching tests revealed that O2?? play a main role in degradation of BPA. Based on the experimental results, the photo-catalytic mechanism is proposed and the degradation path of BPA is revealed.
- Chen, Rufen,Liu, Hui,Lu, Bin,Wang, Yun,Xiao, Bing,Xu, Minghao
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- One-Pass Conversion of Benzene and Syngas to Alkylbenzenes by Cu–ZnO–Al2O3 and ZSM-5 Relay
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Alkylbenzenes have a wide range of uses and are the most demanded aromatic chemicals. The finite petroleum resources compels the development of production of alkylbenzenes by non-petroleum routes. One-pass selective conversion of benzene and syngas to alkylbenzenes is a promising alternative coal chemical engineering route, yet it still faces challenge to industrialized applications owing to low conversion of benzene and syngas. Here we presented a Cu–ZnO–Al2O3/ZSM-5 bifunctional catalyst which realizes one-pass conversion of benzene and syngas to alkylbenzenes with high efficiency. This bifunctional catalyst exhibited high benzene conversion (benzene conversion of 50.7%), CO conversion (CO conversion of 55.0%) and C7&C8 aromatics total yield (C7&C8 total yield of 45.0%). Characterizations and catalytic performance evaluations revealed that ZSM-5 with well-regulated acidity, as a vital part of this Cu–ZnO–Al2O3/ZSM-5 bifunctional catalyst, substantially contributed to its performance for the alkylbenzenes one-pass synthesis from benzene and syngas due to depress methanol-to-olefins (MTO) reaction. Furthermore, matching of the mass ratio of two active components in the dual-function catalyst and the temperature of methanol synthesis with benzene alkylation reactions can effectively depress the formation of unwanted by-products and guarantee the high performance of tandem reactions. Graphic Abstract: [Figure not available: see fulltext.]
- Han, Tengfei,Xu, Hong,Liu, Jianchao,Zhou, Ligong,Li, Xuekuan,Dong, Jinxiang,Ge, Hui
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p. 467 - 479
(2021/05/21)
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- Formation of Catalytically Active Nanoparticles under Thermolysis of Silver Chloroplatinate(II) and Chloroplatinate(IV)
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The thermal behaviour of Ag2 [PtCl4 ] and Ag2 [PtCl6 ] complex salts in inert and reducing atmospheres has been studied. The thermolysis of compounds in a helium atmosphere is shown to occur in two stages. At the first stage, the complexes decompose in the temperature range of 350–500?C with the formation of platinum and silver chloride and the release of chlorine gas. At the second stage, silver chloride is sublimated in the temperature range of 700–900?C, while metallic platinum remains in the solid phase. In contrast to the thermolysis of Ag2 [PtCl6 ], the thermal decomposition of Ag2 [PtCl4 ] at 350?C is accompanied by significant heat release, which is associated with disproportionation of the initial salt to Ag2 [PtCl6 ], silver chloride, and platinum metal. It is confirmed by DSC measurements, DFT calculations of a suggested reaction, and XRD. The thermolysis of Ag2 [PtCl4 ] and Ag2 [PtCl6 ] compounds is shown to occur in a hydrogen atmosphere in two poorly separable steps. The compounds are decomposed within 170–350?C, and silver and platinum are reduced to a metallic state, while a metastable single-phase solid solution of Ag0.67Pt0.33 is formed. The catalytic activity of the resulting nanoalloy Ag0.67Pt0.33 is studied in the reaction of CO total (TOX) and preferential (PROX) oxidation. Ag0.67Pt0.33 enhanced Pt nano-powder activity in CO TOX, but was not selective in CO PROX.
- Filatov, Evgeny,Smirnov, Pavel,Potemkin, Dmitry,Pishchur, Denis,Kryuchkova, Natalya,Plyusnin, Pavel,Korenev, Sergey
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- Glycerol oxidation-assisted electrochemical CO2 reduction for the dual production of formate
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The sluggish oxygen evolution reaction (OER) is one of the main bottlenecks for efficient CO2 electroreduction (CO2ER). Seeking a suitable organic oxidation reaction with a lower redox potential to replace the OER is a promising method to boost the overall efficiency of the CO2ER. Here, we propose a method of substituting the OER with a glycerol oxidation reaction (GOR) for the CO2ER to achieve the coproduction of formate at both the cathode and anode. A two-electrode GOR-assisted CO2ER system is successfully established with a Ni foam-supported surface-sulfurized nickel–cobalt hydroxide nanoneedle catalytic anode (Ni0.33Co0.67(OH)2@HOS/NF) and a BiOI cathode. The simultaneous formation of formate from the anodic GOR and cathodic CO2ER with faradaic efficiencies (FEs) of 90% and 92%, respectively, is obtained at a cell voltage of 1.9 V (22.4 mA cm?2). More significantly, an overall electricity-to-formate energy conversion efficiency of 110% is obtained in our GOR-assisted CO2ER system. This work not only proposes an energy- and atom-efficient method for the CO2ER but also provides new insights for developing highly active non-noble metal catalysts for the GOR.
- Cheng, Jiong,Jin, Fangming,Pei, Yuhou,Pi, Zhenfeng,Zhong, Heng
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supporting information
p. 1309 - 1319
(2022/02/01)
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- Facile preparation of porous hollow CoxMn3-xO4 normal-reverse coexisted spinel for toluene oxidation
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A facile method for the preparation of porous hollow CoxMn3-xO4 normal-reverse coexisted spinel is developed. The CoxMn3-xO4 catalysts with different morphologies can be prepared via adjusting the Co/Mn molar ratio using mixed carbonates as the precursors. The as-prepared CoxMn3-xO4 catalysts exhibit excellent catalytic activities for toluene oxidation due to the synergistic effect of abundant oxygen vacancies and the optimal molar ratio of Co3+/Mn2+–Co2+/Mn3+ coupled redox ion pairs. The porous hollow hierarchical structure of CoxMn3-xO4 is conducive to maintain good long-term structural stability and activity stabilities. The catalytic activity of CoxMn3-xO4 shows no significant loss during the 100 h of on-stream stability test and the 5 vol% water vapor inhibition test, showing excellent anti-sintering ability, high-efficiency mass transfer ability and anti-moisture ability.
- Gu, Wenxiu,Li, Chenqi,Qiu, Jianhao,Yao, Jianfeng
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- Syntheses of two copper metal-organic frameworks with tri(1,2,4-triazole) and biscarboxylate and graphene oxide composites for decomposition of dye by visible-light driven and ultrasonic assisted
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Two crystalline and nano-sized new Cu(II) MOFs {[Cu(ttpa)(1,3-bdc)(H2O)]·CH3OH}n (Cu(ttpa)-1) and {[Cu(ttpa)(mip)(H2O)]?2H2O} (Cu(ttpa)-2) were prepared and characterized (ttpa ?= ?tris(4-(1,2,4-triaz
- Hu, Chuan-Jiang,Li, Bao-Long,Li, Hai-Yan,Li, Le-Yan,Ma, Li-Xiao,Zha, Miao,Zhou, Wen-Jing
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- Investigating the effects of various synthesis routes on morphological, optical, photoelectrochemical and photocatalytic properties of single-phase perovskite BiFeO3
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Herein, various BiFeO3 morphologies, including sheet-like, coral-like and rod-like structures, were synthesized via co-precipitation (CP), hydrothermal (HT), and sol-gel (SG) synthesis routes, respectively. The as-synthesized samples were characterized by physicochemical techniques to investigate their crystal structure, optical and photoelectrochemical properties. The SG-BiFeO3 sample exhibited remarkable direct sunlight photocatalytic degradation of phenol (98.95%), superior to those of the HT-BiFeO3 (77.4%) and CP-BiFeO3 (66.9%) in 120 min. The SG-BiFeO3 sample was the most effective among all due to the lower energy band gap value and highest separation of photogenerated charge carriers, which was validated by the UV–vis absorption, photoluminescence (PL) and photoelectrochemical measurements. The recycling and ferric (Fe3+) ion leakage test suggested that the SG-BiFeO3 sample was highly stable for up to six consecutive runs. The radical scavenger studies implied that the photogenerated hole (h+), hydrogen peroxide (H2O2) and hydroxyl radicles (?OH) were the dominant reactive species. Finally, based on these, a possible photocatalytic mechanism for phenol degradation over SG-BiFeO3 sample was also postulated.
- Chang Chien, Shui-Wen,Jaffari, Zeeshan Haider,Kumar, Dileep,Lam, Sze-Mun,Ng, Ding-Quan
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- Relationship between substrate type and BDD electrode structure, performance and antibiotic tetracycline mineralization
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To comprehensively understand the relationship between substrate type and boron doped diamond (BDD) electrode structure, performance and antibiotic tetracycline mineralization, this work made a systematic evaluation of BDD electrodes prepared by the same process but based on different substrates, namely Si/BDD, Ta/BDD, Nb/BDD and Ti/BDD, in terms of microstructure, electrochemical properties, antibiotic tetracycline mineralization and accelerated service life. The results show that the physical and chemical properties of substrates have significant impacts on BDD film growth and microstructure. The substrate and film surface characteristics determined the physicochemical properties of BDD electrode. The growth rate of BDD film follows the sequence order as Si > Ta > Nb ? Ti. Ti/BDD electrode shows the higher oxygen evolution potential, lower background current, smaller electron transfer resistance, lower surface activity and shorter service life. Tetracycline can be completely removed by direct electron transfer or free radical mediated oxidization. On Ti/BDD electrode tetracycline removal and current efficiency are the second only to Si/BDD and the lowest electricity consumption can be obtained. Nb/BDD electrode shows slightly better performance than Ta/BDD electrode. Furthermore, the anode failure mode of Ti/BDD electrode was revealed.
- Chen, Yinhao,Li, Zhishen,Liu, Fangmu,Liu, Libin,Long, Hangyu,Ma, Li,Tan, Jilin,Wei, Qiuping,Yang, Wanlin,Yu, Zhiming,Zhou, Kechao
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- Fabrication of TlSnI3/C3N4 nanocomposites for enhanced photodegradation of toxic contaminants below visible light and investigation of kinetic and mechanism of photocatalytic reaction
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The use of sufficient solar irradiation for the semiconductor photodegradation of organic pollutants is an excellent technique to tackle worldwide water contamination. Photocatalysis is an eco-friendly method that is familiar for the breakdown of toxic pollutants in sewage. Many semiconductor heterojunctions have been widely employed to intensify photocatalytic efficiency compared to single semiconductors. Polymeric semiconductors such as graphitic carbon nitride (g-C3N4) have been considered inspirational applicants due to their easily adjustable electronic structure and adaptable optical absorption properties. Disadvantages of the current photocatalytic method, which limit their uses, include the rapid recombination, low emigration ability of the photo-generated electron-hole, and low use of visible radiation. The current study designates the preparation of novel TlSnI3/g-C3N4 nanocomposites by ultrasound-assisted coprecipitation technique. The bandgap was estimated at 2.7 eV for pristine g-C3N4. The bandgap of nanocomposite was decreased to 2.5 eV by enhancing TlSnI3 content due to the narrow bandgap of TlSnI3 (2.3 eV). This nanocomposite possesses a high ability to decompose organic dyes due to its relevant bandgap being a prominent catalyst for water treatment. The photocatalytic ability of TlSnI3/C3N4 was examined over the removal of Methylene Blue (MB), Malachite Green (MG), and Rhodamine B (RhB) under visible light. The as-synthesized TlSnI3/C3N4 nanocomposites exposed better photocatalytic performance than the pure TlSnI3 and C3N4.
- Ghanbari, Mojgan,Salavati-Niasari, Masoud,Yousefzadeh, Fatemeh,Yousif, Qahtan A.
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- Hydrothermally grown α-MoO3 microfibers for photocatalytic degradation of methylene blue dye
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Adsorption and photodegradation efficiency of α-MoO3 microfibers towards methylene blue (MB) dye in the aqueous solution were reported. To obtain high-quality α-MoO3 microfibers, an aqueous solution of (NH4)6Mo7O24·4H2O and citric acid was hydrothermally treated (180 °C, 12 h) in the presence of HNO3. The possible growth mechanism of microfibers in the hydrothermal reaction is explained. XRD and TEM studies provide shreds of evidence that microfibers have crystallized in a pure orthorhombic phase and grown up in the direction of [0 0 1]. The structural bonding between molybdenum and oxygen constituent elements of microfibers was further confirmed by XPS, FTIR, and Raman techniques. The estimated optical band gap of α-MoO3 microfibers (Eg = 2.68 eV) lies in the visible region, making them suitable for visible light photocatalytic application. MB adsorption and degradation capacity of microfibers were performed in the dark and light, respectively. The photocatalytic properties revealed that 90 % MB dye was degraded within 120 min illumination. Moreover, the good photocatalytic recycling capability of α-MoO3 microfibers makes them a promising photocatalyst to eliminate organic pollutants from water.
- Dewangan, Khemchand,Singh, Dadan,Satpute, Nilesh,Singh, Ritika,Jaiswal, Adhish,Shrivas, Kamlesh,Bahadur, Indra
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- Novel LaCr substituted Mhexaferrite photocatalyst for decontamination of organic pollutants by peroxymonosulfate activation
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Element engineering in Mhexaferrite system has been demonstrated as an effective technique to boost catalytic activation of peroxymonosulfate (PMS). This study aimed at catalytic activation of PMS under LED irradiation using a novel LaCr substituted Mhexaferrite photocatalyst (BLCF-NPs) for degradation of organic pollutants in water systems. The chemical and physical characteristics of BLCF catalysts, the effects of BLCF's heterogeneous catalyst, PMS, pH, and pollutant concentration on degradation performance, reusability and stability of BLCF-NPs were systematically investigated. Importantly, under LED illumination, the sample C3 activated PMS to degrade MO more efficiently (99.99% within 80 min) and stably than reported Mhexaferrite NPs, with a first-order-kinetic rate constant (k = 11.41 10?2 min?1). The PMS/LED/BLCF-NPs system was improved effectively in a wide pH range from 3 to 10. Radical quenching experiments demonstrated that SO4[rad]? played a dominant role in MO degradation. This research paves the way for developing high-efficiency catalysts, as well as making Mhexaferrites viable options for pollutants removal.
- Ali, Jazib,Ashraf, Ghulam Abbas,Chen, Jing,Guo, Hai,Hassan, Muhammad,Li, Lianjie,Rasool, Raqiqa Tur,Zhang, Lanting
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- The role of remote flavin adenine dinucleotide pieces in the oxidative decarboxylation catalyzed by salicylate hydroxylase
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Salicylate hydroxylase (NahG) has a single redox site in which FAD is reduced by NADH, the O2 is activated by the reduced flavin, and salicylate undergoes an oxidative decarboxylation by a C(4a)-hydroperoxyflavin intermediate to give catechol. We report experimental results that show the contribution of individual pieces of the FAD cofactor to the observed enzymatic activity for turnover of the whole cofactor. A comparison of the kinetic parameters and products for the NahG-catalyzed reactions of FMN and riboflavin cofactor fragments reveal that the adenosine monophosphate (AMP) and ribitol phosphate pieces of FAD act to anchor the flavin to the enzyme and to direct the partitioning of the C(4a)-hydroperoxyflavin reaction intermediate towards hydroxylation of salicylate. The addition of AMP or ribitol phosphate pieces to solutions of the truncated flavins results in a partial restoration of the enzymatic activity lost upon truncation of FAD, and the pieces direct the reaction of the C(4a)-hydroperoxyflavin intermediate towards hydroxylation of salicylate.
- Brand?o, Tiago A. S.,Nagem, Ronaldo A. P.,Pereira, Mozart S.,Richard, John P.,de Araújo, Simara S.
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- 3D structured TiO2-based aerogel photocatalyst for the high-efficiency degradation of toluene gas
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Photocatalytic technology is a green , environmentally friendly, energy-saving technology, which is considered to be an ideal method for removing volatile organic compounds (VOCs). At present, photocatalytic technology mostly uses powdered catalysts, which is not conducive to recycling and restricts the contact between the gas and catalyst. In this work, a three-dimensional (3D)-structured TiO2-based aerogel with TiO2 as the main body and all the components beneficial to photocatalysis was prepared for the first time. Under simulated sunlight irradiation, the toluene-removal rate of the Pt-loaded TiO2 and reduced graphene oxide (RGO) composite aerogel (denoted as Pt-TiO2/RGO aerogel, or PTA thereafter) was 60.47% higher than that of the pure RGO aerogel, and 56.03% higher than that of the bare TiO2 nanofibers. The block-shaped composite aerogel could be easily recycled, and the C/C0 of toluene using the recycled sample decreased by only 5.31% in the 5th run. The Pt-TiO2/RGO composite aerogel had the highest photocatalytic degradation rate of toluene with a relative humidity (RH) of 60-80%, which is conducive to the purification of VOCs in high-humidity areas. The 3D aerogel enriches the contact between the solid photocatalyst and the toluene molecules, and also solves the problem of low adhesion between the catalyst and the carrier. This work provides a new perspective for the efficient removal of toluene gas by constructing a highly active 3D TiO2 aerogel with an increased gas-solid reaction rate.
- Dai, Li,Guan, Jie,Li, Shijie,Li, Xueying,Yu, Wei,Zhang, Li
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p. 2272 - 2281
(2022/02/16)
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- Synthesis, thermal behavior in oxidative and pyrolysis conditions, spectroscopic and DFT studies of some alkaline earth metals p-aminobenzoate complexes using TG-DTA, DSC, PXRD and EGA (TG-FTIR) techniques
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p-aminobenzoic acid is a substance widely used in several areas, such as catalysis, biomarkers, magnetic materials, luminescent materials and biological applications. p-aminobenzoate complexes with alkaline earth metal were synthesized and the thermal and pyrolysis behavior was studied using thermoanalytical and spectroscopic techniques. Based on TG/DTG-DTA and EGA results, the thermal decomposition mechanisms of the compounds were proposed under both atmospheres studied. The main gaseous products identified by EGA in both study conditions were H2O, Aniline, CO and CO2. From DSC analysis, it was possible to measure the enthalpies of dehydration and evaluate the phase transitions of the magnesium complex. FTIR data suggest that metal-ligand coordination occurs through carboxylate group by different ways. The coordination modes suggested by experimental FTIR data were supported by DFT study. The X-ray diffraction powder patterns show that the barium compound was obtained in amorphous state, while the other compounds have a crystalline structure.
- Caires, Flávio J.,Fernandes, Richard P.,Gaspari, Ana P. S.,Ionashiro, Massao,Isquibola, Guilherme,Machado, Antonio E. H.,Teixeira, José Augusto
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- Investigation of photocatalytic mineralisation of Acridine Yellow G dye by BaCrO4 in the presence of eco-friendly LEDs irradiation
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Degradation of toxic organic pollutants and dyes from industrial wastewater by photocatalysis is an environmentally friendly technique. The degradation of Acridine Yellow G (AYG) was investigated in aqueous solutions employing BaCrO4 as a heterogeneous photocatalyst under eco-friendly LED irradiation. We studied the mineralisation kinetics of AYG by monitoring the dye concentration and chemical oxygen demand (COD) as a function of time. The impact of pH, concentrationdye, reactants, catalyst, Fenton reagent, salt effect, and temperature on the kinetics were investigated. The initial addition of optimal amounts of hydrogen peroxide and potassium persulfate increased the degradation rate, while NaCl and Na2CO3 retarded the reaction. The efficiency of visible light, LED (12 ?W) irradiation, compared with the traditional visible light source, the halogen lamp (500 ?W). At the optimum pH 10, the AYG degradation obeyed pseudo-first-order kinetics. With BaCrO4 asa heterogeneous photocatalyst, complete mineralisation of AYG was achieved in 35 ?min. This process is green, eco-friendly, and the catalyst is easily recoverable and reusable five times without loss of catalytic efficiency.
- Ameta, Keshav Lalit,Gupta, Premlata,Jonnalagadda, Sreekantha B.,Pare, Brijesh,Solanki, Vijendra Singh
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- Binary Au–Cu Reaction Sites Decorated ZnO for Selective Methane Oxidation to C1 Oxygenates with Nearly 100% Selectivity at Room Temperature
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Direct and efficient oxidation of methane to methanol and the related liquid oxygenates provides a promising pathway for sustainable chemical industry, while still remaining an ongoing challenge owing to the dilemma between methane activation and overoxidation. Here, ZnO with highly dispersed dual Au and Cu species as cocatalysts enables efficient and selective photocatalytic conversion of methane to methanol and one-carbon (C1) oxygenates using O2 as the oxidant operated at ambient temperature. The optimized AuCu–ZnO photocatalyst achieves up to 11225 μmol·g–1·h–1 of primary products (CH3OH and CH3OOH) and HCHO with a nearly 100% selectivity, resulting in a 14.1% apparent quantum yield at 365 nm, much higher than the previous best photocatalysts reported for methane conversion to oxygenates. In situ EPR and XPS disclose that Cu species serve as photoinduced electron mediators to promote O2 activation to ?OOH, and simultaneously that Au is an efficient hole acceptor to enhance H2O oxidation to ?OH, thus synergistically promoting charge separation and methane transformation. This work highlights the significances of co-modification with suitable dual cocatalysts on simultaneous regulation of activity and selectivity.
- Gong, Zhuyu,Liu, Huifen,Luo, Lei,Ma, Jiani,Tang, Junwang,Xing, Jialiang,Xu, Youxun
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supporting information
p. 740 - 750
(2022/01/03)
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- Ethanol Steam Reforming by Ni Catalysts for H2 Production: Evaluation of Gd Effect in CeO2 Support
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Abstract: Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the role of gadolinium on ethanol conversion, H2 selectivity, and carbon formation on ethanol steam reforming reaction. For this, catalysts containing 5 wt% of Ni impregnated on supports of ceria modified with different amounts of Gd (1, 5, and 10 wt%) were used. Ex-situ studies of XRPD suggest an increase of the lattice parameters, indicating a solid solution formation between Gd and Ce. Results of TPR showed an increase in metal-support interactions as the content of Gd increased. In situ XRPD studies indicated the formation of a GdNiO ternary phase for the catalysts containing Gd, which is in agreement with the results obtained by XANES. The catalysts were tested at three temperatures: 400?°C, 500?°C, and 600?°C. The conversion and productivity showed dependence with the Gd content and also with the temperature of the reaction. After the catalytic tests, catalysts containing Gd presented filamentous carbon possible due to a change in the reaction pathway. The highest ethanol conversion and H2 productivity were obtained at 600?°C for all catalysts and the best catalyst at this temperature was 5Ni_5GdCeO2. The promising performance of this catalyst may be associate with the lowest formation of GdNiO ternary phase, among the catalysts containing Gd, which means more Ni0 active species available to convert ethanol. Graphical Abstract: [Figure not available: see fulltext.]
- Assaf, Elisabete M.,Ferreira, Gabriella R.,Lucrédio, Alessandra F.,Nogueira, Francisco G. E.
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- The influence of different carbonate ligands on the hydrolytic stability and reduction of platinum(
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Pt(iv) complexes bearing axial carbonate linkages have drawn much attention recently. A synthetic method behind this allows the hydroxyl group of bioactive ligands to be attached to the available hydroxyl group of Pt(iv) complexes, and the rapid release of free drugs is achieved after the reduction of carbonate-linked Pt(iv) complexes. Further understanding on the properties of Pt(iv) carbonates such as hydrolytic stability and reduction profiles, however, is hindered by limited research. Herein, six mono-carbonated Pt(iv) complexes in which the carbonate axial ligands possess various electron-withdrawing powers were synthesized, and the corresponding mono-carboxylated analogues were also prepared as references to highlight the different properties. The influence of the coordination environment towards the hydrolysis and reduction rate of Pt(iv) carbonates and carboxylates was explored. The mono-carbonated Pt(iv) complexes are both less stable and reduced faster than the corresponding mono-carboxylated ones. Moreover, the hydrolysis and reduction profiles are dependent not only on the electron-withdrawing ability of the carbonates but also on the nature of the opposite axial ligands. Besides, the exploration of the hydrolytic pathway for Pt(iv) carbonates suggests that the process proceeds by an attack of OH? on the carbonyl carbon, followed by elimination, which is different from that of Pt(iv) carboxylates. This study provides some information on the influence of axial carbonate ligands with different electron-withdrawing abilities on the properties of the Pt(iv) center, which may inspire new thoughts on the design of “multi-action” Pt(iv) prodrugs.
- Chen, Shu,Deng, Zhiqin,Ng, Ka-Yan,Tse, Man-Kit,Yao, Houzong,Zhou, Qiyuan,Zhu, Guangyu
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supporting information
p. 885 - 897
(2022/02/01)
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- Rational Design of Zinc/Zeolite Catalyst: Selective Formation of p-Xylene from Methanol to Aromatics Reaction
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The production of p-xylene from the methanol to aromatics (MTA) reaction is challenging. The catalytic stability, which is inversely proportional to the particle size of the zeolite, is not always compatible with p-xylene selectivity, which is inversely proportional to the external acid sites. In this study, based on a nano-sized zeolite, we designed hollow triple-shelled Zn/MFI single crystals using the ultra-dilute liquid-phase growth technique. The obtained composites possessed one ZSM-5 layer (≈30 nm) in the middle and two silicalite-1 layers (≈20 nm) epitaxially grown on two sides of ZSM-5, which exhibited a considerably long lifetime (100 % methanol conversion >40 h) as well as an enhanced shape selectivity of p-xylene (>35 %) with a p-xylene/xylene ratio of ≈90 %. Importantly, using this sandwich-like zeolite structure, we directly imaged the Zn species in the micropores of only the ZSM-5 layer and further determined the specific structure and anchor location of the Zn species.
- Chen, Biaohua,Chen, Congmei,Chen, Xiao,Hou, Yilin,Hu, Xiaomin,Li, Jing,Qian, Weizhong,Sun, Wenjing,Wang, Ning,Yang, Yifeng,Zhang, Lan
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supporting information
(2022/02/16)
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- CeO2 Facet-Dependent Surface Reactive Intermediates and Activity during Ketonization of Propionic Acid
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CeO2 rods, octahedrons, and cubes exposing well-defined (110), (111), and (100) surfaces, respectively, were synthesized and investigated for the catalytic ketonization of propionic acid. The intrinsic ketonization rates at 350 °C on the rods, octahedrons, and cubes are 54.3, 40.4, and 25.1 mmol·m-2·h-1, respectively, indicating that the (110) facet is the most active surface for ketonization. The reaction was tracked by both in situ infrared and mass spectroscopies under transient conditions, and the results showed that monodentate propionate, a minority surface species, is responsible for the formation of 3-pentanone. In contrast, bidentate propionate, a dominant species on all three surfaces, appears to a spectator for ketonization. Moreover, the ketonization activity can be correlated with relative concentration of monodentate propionate. A density functional theory study showed that the relative concentration of monodentate propionate (or the adsorption energy difference between monodentate and bidentate configurations) at high coverages is strongly dependent on the surface geometry. The stability of monodentate propionate on the (110) surface exposing both the O and Ce sites in the outermost layer with the well-separated Ce sites exhibits little dependence on the propionate coverage. In contrast, strong steric hindrance due to the top layer O atom and the closely packed Ce atoms in (111) destabilizes monodentate propionate significantly at high coverages. This study demonstrates that the surface geometrical structure of CeO2 can determine the abundance of the active monodentate propionate, which, in turn, will determine the catalytic activity of CeO2 for ketonization.
- Guo, Yonghua,Qin, Yuyao,Liu, Huixian,Wang, Hua,Han, Jinyu,Zhu, Xinli,Ge, Qingfeng
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p. 2998 - 3012
(2022/03/03)
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- Photolabile 2-(2-Nitrophenyl)-propyloxycarbonyl (NPPOC) for Stereoselective Glycosylation and Its Application in Consecutive Assembly of Oligosaccharides
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A photolabile protecting group (PPG) 2-(2-nitrophenyl)-propyloxycarbonyl (NPPOC) was explored in glycosylation and applied in the consecutive synthesis of oligosaccharides. NPPOC displays a strong neighboring group participation (NGP) effect to facilitate the construction of 1,2-trans glycosides in excellent yield. Notably, NPPOC could be efficiently removed by photolysis, and the deprotection conditions are friendly to typical protecting groups. A branched and asymmetric oligomannose Man6 was rapidly prepared, and the consecutive assembly of oligosaccharides without intermediate purification was further investigated owing to the compatibility conditions between NPPPOC's photolysis and glycosylation.
- Wang, Jincai,Feng, Yingle,Sun, Taotao,Zhang, Qi,Chai, Yonghai
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supporting information
p. 3402 - 3421
(2022/03/02)
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- Catalytic wet air oxidation of D-glucose by perovskite type oxides (Fe, Co, Mn) for the synthesis of value-added chemicals
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The conversion of common biomasses derived, as D-glucose, into value-added chemicals has received highest attention in the last few years. Among all processes, the catalytic wet air oxidation (CWAO) of derived biomasses using noble metal-based heterogeneo
- Geobaldo, Francesco,Pirone, Raffaele,Russo, Nunzio,Scelfo, Simone
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- Electrochemical Formation and Activation of Hydrogen Peroxide from Water on Fluorinated Tin Oxide for Baeyer-Villiger Oxidation Reactions
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The two-electron oxidation of water (2e-WOR) has been studied in the past as a possible method for the alternative preparation of hydrogen peroxide. Often, fluorinated tin oxide (FTO) is used as an anode and FTO itself was found also to be active for 2e-WOR. Because one use of H2O2is as an oxygen donor for Baeyer-Villiger oxidation of ketones catalyzed by tin compounds and materials, presently we were interested in studying the use of in situ formed H2O2for these reactions. First, the formation of H2O2was verified in an acetonitrile/water solvent in a 2e-WOR reaction, which is more efficient than a comparable reaction in water in terms of the H2O2concentration attained and faradaic efficiency at comparable potentials, that is, ～3 V vs SHE. Second, initial studies on oxygenation of reactive substrates such as sulfides showed normalized reaction rates (NRRs) for two-electron oxidation reactions that were about 3 times higher than the NRR for H2O2formation, indicating the formation of an active oxygen-donating or oxidizing species on the electrode surface prior to the formation and release of H2O2into solution. Third, the Baeyer-Villiger oxygenation of 2-adamantanone at 2.1 V versus SHE in acetonitrile/water showed both the formation of the expected lactone product and hydroxylation at both tertiary and secondary C-H bonds. Hydroxylation is most easily explained by the presence of hydroxyl radical species as supported by the formation of a spin adduct and its identification by electron paramagnetic resonance. However, the potential used, 2.1 V versus SHE, is an underpotential for the formation of a solvated hydroxyl radical in solution, thereby leading to the conclusion that surface-bound hydroxyl species, OH*, are those that are reactive for the apparent one-electron water oxygenation reaction. Fourth, it was shown that although H2O2can be thermally activated on FTO as a catalyst to a minor degree, electrochemical activation is by far more significant, leading to the use of FTO as an electrochemical catalyst for activation of H2O2for the Baeyer-Villiger oxygenation and also alkene epoxidation.
- Herman, Adi,Mathias, Jenny-Lee,Neumann, Ronny
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p. 4149 - 4155
(2022/04/12)
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- Kinetically Controlled Synthesis of Rhodium Nanocrystals with Different Shapes and a Comparison Study of Their Thermal and Catalytic Properties
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We report the synthesis of Rh nanocrystals with different shapes by controlling the kinetics involved in the growth of preformed Rh cubic seeds. Specifically, Rh nanocrystals with cubic, cuboctahedral, and octahedral shapes can all be obtained from the same cubic seeds under suitable reduction kinetics for the precursor. The success of such a synthesis also relies on the use of a halide-free precursor to avoid oxidative etching, as well as the involvement of a sufficiently high temperature to remove Br- ions from the seeds while ensuring adequate surface diffusion. The availability of Rh nanocrystals with cubic and octahedral shapes allows for an evaluation of the facet dependences of their thermal and catalytic properties. The data from in situ electron microscopy studies indicate that the cubic and octahedral Rh nanocrystals can keep their original shapes up to 700 and 500 °C, respectively. When tested as catalysts for hydrazine decomposition, the octahedral nanocrystals exhibit almost 4-fold enhancement in terms of H2 selectivity relative to the cubic counterpart. As for ethanol oxidation, the order is reversed, with the cubic nanocrystals being about three times more active than the octahedral sample.
- Zhao, Ming,Chen, Zitao,Shi, Yifeng,Hood, Zachary D.,Lyu, Zhiheng,Xie, Minghao,Chi, Miaofang,Xia, Younan
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p. 6293 - 6302
(2021/05/07)
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- Carbon monoxide as an intermediate product in the photocatalytic steam reforming of methane with lanthanum-doped sodium tantalate
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Photocatalytic steam reforming of methane (PSRM) has been studied as an attractive method to produce hydrogen by utilizing photoenergy like solar energy at around room temperature with metal-loaded photocatalysts, where methane and water are selectively converted to carbon dioxide and hydrogen. In the present study, we used a PSRM system using a flow reactor at around room temperature to yield the partially oxidized product, carbon monoxide (CO). It was found that some La-doped NaTaO3 samples can produce carbon monoxide constantly in addition to hydrogen and carbon dioxide. Among the prepared samples, a La(2 mol%)-doped NaTaO3 photocatalyst without any cocatalyst exhibited the highest photocatalytic activity and the highest CO selectivity of 24%. The CO yield depended on the photocatalysts and the reaction conditions. Suitable reaction conditions for CO yield were high light intensity, a higher flow rate, and a moderately high methane/water ratio. Some additional reaction tests revealed that water gas shift (WGS) can take place as an undesirable successive reaction, i.e., the produced carbon monoxide can successively react with water to form carbon dioxide, which would restrict the CO yield significantly.
- Anzai, Akihiko,Sarwana, Wirya,Takami, Daichi,Yamamoto, Akira,Yoshida, Hisao
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p. 5534 - 5542
(2021/08/24)
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- Single-Phase Formation of Rh2O3 Nanoparticles on h-BN Support for Highly Controlled Methane Partial Oxidation to Syngas
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Single-phase formation of active metal oxides on supports has been vigorously pursued in many catalytic applications to suppress undesired reactions and to determine direct structure-property relationships. However, this is difficult to achieve in nanoscale range because the effect of non-uniform metal-support interfaces becomes dominant in the overall catalyst growth, leading to the nucleation of various metastable oxides. Herein, we develop a supported single-phase corundum-Rh2O3(I) nanocatalyst by utilizing controlled interaction between metal oxide and h-BN support. Atomic-resolution electron microscopy and first-principle calculation reveal that single-phase formation occurs via uniform and preferential attachment of Rh2O3(I) (110) seed planes on well-defined h-BN surface after decomposition of rhodium precursor. By utilizing the Rh/h-BN catalyst in methane partial oxidation, syngas is successfully produced solely following the direct route with keeping a H2/CO ratio of 2, which makes it ideal for most downstream chemical processes.
- Kang, Dohun,Kang, Sungsu,Kim, Ji Soo,Kim, Younhwa,Lee, Hyunjoo,Lee, Kyung Rok,Park, Jungwon,Song, Chyan Kyung,Sung, Jongbaek,Yi, Jongheop
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supporting information
p. 25411 - 25418
(2021/10/25)
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- Combination of reduction-deposition Pd loading and zeolite dealumination as an effective route for promoting methane combustion over Pd/Beta
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Catalytic removal of trace methane emission over supported Pd catalysts has drawn much attention over the years. For practical application, high activity, excellent thermal stability and outstanding water resistance are always desirable. Herein, we report a facile route for simultaneously improving the activity, stability and water resistance of the zeolite supported Pd catalyst through the combination of reduction-deposition Pd loading and support dealumination. This combination strategy leads to highly dispersed and stable PdO nanoparticles with strong interaction with the Beta support, rich active Pdn+ (0 ?1 g?1 and 1 vol.% CH4 feed concentration, enhanced long-term stability, and greatly improved water resistance with a low 0.5 wt.% Pd loading amount. Such a synthetic strategy is expected to provide a useful approach towards designing efficient zeolite supported noble metal catalysts.
- Zhang, Liling,Chen, Junfei,Guo, Xiaomin,Yin, Shumeng,Zhang, Meng,Rui, Zebao
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p. 119 - 125
(2020/07/30)
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- Unraveling mechanistic aspects of the total oxidation of methane over Mn, Ni and Cu spinel cobaltites via in situ electrical conductivity measurements
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Mn, Ni and Cu cobaltite spinels were synthesized by coprecipitation, characterized and evaluated in the total oxidation of methane. To gain a deeper insight into their catalytic behavior, their electrical conductivity was studied as a function of temperature and oxygen partial pressure, and was followed with time during sequential exposures to different gases in conditions close to those used for the catalytic tests. The Ni cobaltite is in a metallic conductivity state and cannot be reduced in the reaction conditions, suggesting that it functions via a suprafacial mechanism. The Cu cobaltite behaves as a p-type semiconductor, but it is not reduced under the reaction mixture at the reaction temperature of 350 °C, suggesting that, at least in these conditions, the suprafacial mechanism is operating. The Mn cobaltite has an n-type semiconducting character and is reduced in the reaction conditions, suggesting that a heterogeneous redox mechanism is involved.
- Mihai, Marius-Alexandru,Culita, Daniela Cristina,Atkinson, Irina,Papa, Florica,Popescu, Ionel,Marcu, Ioan-Cezar
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- Highly Active and Stable Palladium Catalysts Supported on Surface-modified Ceria Nanowires for Lean Methane Combustion
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An efficient strategy was presented to synthesize highly active palladium catalyst supported on ceria nanowires modified by organosilanes (abbreviated as Pd/CeO2NWs@SiO2) for lean methane combustion. It is found that such a surface-modified strategy can significantly improve the dispersion of surface palladium species and strengthen the concentration of active surface-adsorbed oxygen species via reconstructing the surface microenvironment, invoking an efficient performance for methane oxidation. Under the space velocity of 60,000 mLg?1h?1, 0.5 wt% Pd/CeO2NWs@SiO2 displayed extraordinary catalytic activity with 90 % conversion rate at a temperature of around 327 °C, far lower than that of pristine Pd/CeO2NWs (378 °C) under the same conditions. What's more, unexpected stability was observed under high temperature and the presence of water vapor conditions owing to the intense metal support interaction of Pd/CeO2NWs@SiO2 catalyst. The possible reaction mechanism of lean methane oxidation was probed by in situ DRIFT spectra. It is observed that the pivotal intermediate products (carbonate and carbon oxygenates) generated on Pd/CeO2NWs@SiO2 surface are more readily decomposed into CO2. Importantly, the silicon hydroxyl groups (Si?OH) formed during the reaction can efficiently restrict the generation of the stable Pd(OH)x phase and release more active sites to facilitate the catalytic performance. This study provides a convenient method to design the highly reactive and durable palladium-based catalyst for methane combustion.
- Wu, Mingwei,Li, Wenzhi,Ogunbiyi, Ajibola T.,Guo, Ge,Xue, Fengyang,Chen, Kun,Zhang, Baikai
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p. 664 - 673
(2020/12/01)
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- Efficient photocatalytic conversion of CH4into ethanol with O2over nitrogen vacancy-rich carbon nitride at room temperature
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A record ethanol production rate of 281.6 μmol g?1h?1for the photocatalytic conversion of methane over nitrogen vacancy-rich carbon nitride at room temperature was achieved. Systematic studies demonstrate that the CH4was activated by the highly reactive ˙OH radicals generated,viaH2O2, from the photo-reduction of O2with H2O.
- Yang, Zhongshan,Zhang, Qiqi,Ren, Liteng,Chen, Xin,Wang, Defa,Liu, Lequan,Ye, Jinhua
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supporting information
p. 871 - 874
(2021/02/06)
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- Acid etching induced defective Co3O4as an efficient catalyst for methane combustion reaction
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Development of an effective Co3O4 material as an advanced non-noble metal catalyst for methane combustion has great economic and environmental significance. Herein, a facile acid etching procedure is adapted to engineer a defective Co3O4 possessing both highly exposed surface defects and lattice defects such as abundant oxygen vacancies. The defective structures facilitate an elevated exposure of active surface oxygen and enhanced redox properties. Meanwhile, the acid treatment endows a more acidic surface, which will promote the desorption of the CO2 product. Consequently, an improved activity for methane combustion with a half methane conversion temperature (T50) of 311 °C (33?000 mL g-1 h-1) is obtained for the defective Co3O4, corresponding to the methane conversion rate of 4.1 μmol g-1 s-1, 5.2 times that of the pristine Co3O4. The universality of this strategy is further verified towards a MnO2 catalyst. This study will provide positive guidance for non-noble metal catalyst design in the application of methane combustion. This journal is
- Bao, Liurui,Chang, Le,Yao, Lisha,Meng, Wenhao,Yu, Qiang,Zhang, Xin,Liu, Xuehua,Wang, Xianfen,Chen, Wei,Li, Xingyun
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p. 3546 - 3551
(2021/03/03)
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- Synthesis and Activity of Nanodispersed SnO2–CeO2 Catalyst in the Oxidation Reactions of Carbon Monoxide and Methane
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Abstract: Nanodispersed SnO2–CeO2 catalysts for the oxidation of CO and СН4 were synthesized by coprecipitation in a water–isopropanol solution followed by thermal treatment. It was shown that SnхCe1–хO2 solid solutions based on the crystal lattice of cerium dioxide were formed at x ≤ 0.15. The samples were characterized by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), nitrogen adsorption–desorption, and gas chromatography. The materials had a mesoporous structure: the specific surface area was 52.3–69.7 m2/g, and the total pore volume was 0.073–0.108?cm3/g. When the SnO2 content was greater than 30 mol %, plate-shaped SnO2 particles with sizes greater than 100 nm were formed along with nearly spherical solid solution particles of size 8–10 nm. The synthesized solid solutions were highly active in the oxidation reactions of CO and methane, and they can be used as catalysts and supports.
- Liberman, E. Yu.,Simakina,Moiseev,Izotova,Kon’kova,Grunsky
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p. 155 - 159
(2021/03/15)
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- LaMn1 –xFe xO3 (x = 0–1) Perovskites in Methane and Carbon Monoxide Oxidation Reactions
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Abstract: The LaMn1 –xFexO3 (х = 0–1) perovskites were prepared by the Pechini route and characterized by X-ray diffraction analysis, HR TEM, XPS, and BET. Their catalytic activity was investigated in methane and CO oxidation reactions. According to X-ray analysis data, the samples with х 0.4 were rhombohedral. In the sample with х = 0.4, both of the modifications were present due to a morphotropic phase transformation at х ≈ 0.4. All of the substituted perovskites were characterized with higher specific surface areas and lower normalized catalytic activity in methane and CO oxidations as compared with unsubstituted ones due to surface enrichment with La compounds. The samples with х = 0.6 and 0.8 demonstrated the lowest activity and stability in the catalytic oxidation of methane, which can be due to the accumulation of carbonates and carbon on the surface in the course of methane oxidation and the additional formation of locally ordered structure regions on the surface.
- Isupova,Gerasimov, E. Yu.,Prosvirin
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p. 146 - 154
(2021/03/15)
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- Yttrium stabilization and Pt addition to Pd/ZrO2catalyst for the oxidation of methane in the presence of ethylene and water
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Catalytic oxidation is the most efficient method of minimizing the emissions of harmful pollutants and greenhouse gases. In this study, ZrO2-supported Pd catalysts are investigated for the catalytic oxidation of methane and ethylene. Pd/Y2O3-stabilized ZrO2(Pd/YSZ) catalysts show attractive catalytic activity for methane and ethylene oxidation. The ZrO2support containing up to 8 mol% Y2O3improves the water resistance and hydrothermal stability of the catalyst. All catalysts are characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), O2-temperature-programmed desorption (O2-TPD), and CO-chemisorption techniques. It shows that high Pd dispersion and Pd-PdO reciprocation on the Pd/YSZ catalyst results in relatively high stability.In situdiffuse reflectance infrared Fourier-transform (DRIFT) experiments are performed to study the reaction over the surface of the catalyst. Compared with bimetallic catalysts (Pd?:?Pt), the same amounts of Pd and Pt supported on ZrO2and Y2O3-stabilized ZrO2catalysts show enhanced activity for methane and ethylene oxidation, respectively. A mixed hydrocarbon feed, containing methane and ethylene, lowers the CH4light-off temperature by approximately 80 °C. This shows that ethylene addition has a promotional effect on the light-off temperature of methane.
- Khan, Hassnain Abbas,Hao, Junyu,Tall, Omar El,Farooq, Aamir
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p. 11910 - 11917
(2021/04/06)
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- Fe-O Clusters Anchored on Nodes of Metal–Organic Frameworks for Direct Methane Oxidation
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Direct methane oxidation into value-added organic oxygenates with high productivity under mild condition remains a great challenge. We show Fe-O clusters on nodes of metal–organic frameworks (MOFs) with tunable electronic state for direct methane oxidation into C1 organic oxygenates at 50 °C. The Fe-O clusters are grafted onto inorganic Zr6 nodes of UiO-66, while the organic terephthalic acid (H2BDC) ligands of UiO-66 are partially substituted with monocarboxylic modulators of acetic acid (AA) or trifluoroacetic acid (TFA). Experiments and theoretical calculation disclose that the TFA group coordinated with Zr6 node of UiO-66 enhances the oxidation state of adjacent Fe-O cluster due to its electron-withdrawing ability, promotes the activation of C?H bond of methane, and increases its selective conversion, thus leading to the extraordinarily high C1 oxygenate yield of 4799 μmol gcat?1 h?1 with 97.9 % selectivity, circa 8 times higher than those modulated with AA.
- Zhao, Wenshi,Shi, Yanan,Jiang, Yuheng,Zhang, Xiaofei,Long, Chang,An, Pengfei,Zhu, Yanfei,Shao, Shengxian,Yan, Zhuang,Li, Guodong,Tang, Zhiyong
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supporting information
p. 5811 - 5815
(2021/02/06)
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- LDH derived MgAl2O4 spinel supported Pd catalyst for the low-temperature methane combustion: Roles of interaction between spinel and PdO
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Poor catalytic activity and stability are primary defects of traditional Pd/Al2O3 catalysts for the low-temperature methane combustion. Herein, we developed a facile way to synthesize a MgAl-LDHs derived MgAl2O4 spinel with good crystalline lattice and high surface area, which was used as support of Pd-based catalysts. Catalysts with Mg/Al ratio of 1/3 presented the highest methane combustion activity. It was found the well-crystallized MgAl2O4 spinel promoted the dispersion and crystallization of PdO due to the strong interaction between PdO and support, and the electrophilicity and basicity originated from Mg doping suppressed the sintering of PdO particles, leading to the excellent performance of Pd/MgAl3. Moreover, these factors also inhibited the formation of surface OH- species, therefore, improved the water resistance. Such a synthesis strategy of the Pd/MgxAly derived from LDHs and the roles of MgAl2O4 spinel could pose some meaningful directions for developing high-efficient Pd-based catalysts for the low-temperature methane combustion.
- Song, Jiayu,Wang, Shengping,Xu, Yan,Liu, Qingling,Zhao, Yujun
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- Oxidation of methane to methanol over Pd@Pt nanoparticles under mild conditions in water
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Direct methane oxidation into oxygen-containing chemicals under mild conditions has sparked increasing interest. Here, we report Pd@Pt core-shell nanoparticles that efficiently catalyse the direct oxidation of CH4to CH3OH in water using H2O2as an oxidant under mild conditions. The catalyst presents a methanol productivity of up to 89.3 mol kgcatalyst?1h?1with a high selectivity of 92.4% after 30 min at 50 °C, thus outperforming most of the previously reported catalysts. Electron-enriched Pt species in the Pd@Pt nanoparticles were identified by structural and electronic analysis. Pd in the core donates electrons to Pt, leading to higher rates of methane activation. Based on the results of control experiments and kinetic analysis, a consecutive oxidation pathwayviaa radical mechanism is proposed, which includes initial formation of CH3OOH and CH3OH followed by further oxidation of CH3OH to HCHO, HCOOH, and CO2
- Chen, Jianjun,Chen, Yaoqiang,Collière, Vincent,Lecante, Pierre,Peres, Laurent,Philippot, Karine,Wang, Sikai,Yan, Ning
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p. 3493 - 3500
(2021/06/06)
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- Single-Site vs. Cluster Catalysis in High Temperature Oxidations
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The behavior of single Pt atoms and small Pt clusters was investigated for high-temperature oxidations. The high stability of these molecular sites in CHA is a key to intrinsic structure–performance descriptions of elemental steps such as O2 dissociation, and subsequent oxidation catalysis. Subtle changes in the atomic structure of Pt are responsible for drastic changes in performance driven by specific gas/metal/support interactions. Whereas single Pt atoms and Pt clusters (> ca. 1 nm) are unable to activate, scramble, and desorb two O2 molecules at moderate T (200 °C), clusters 2 scrambling. In contrast, when combustion involves CO, catalysis is dominated by metal clusters, not single Pt atoms.
- Corma, Avelino,Kliewer, Christine,Moliner, Manuel,Rodríguez-Fernández, Aida,Serna, Pedro,Yacob, Sara
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supporting information
p. 15954 - 15962
(2021/06/14)
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- H2O-Built Proton Transfer Bridge Enhances Continuous Methane Oxidation to Methanol over Cu-BEA Zeolite
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Direct oxidation of methane to methanol (DMTM) is a big challenge in C1 chemistry. We present a continuous N2O-DMTM investigation by simultaneously introducing 10 vol % H2O into the reaction system over Cu-BEA zeolites. Combining a D2O isotopic tracer technique and ab initio molecular dynamics (AIMD) simulation, we for the first time demonstrate that the H2O molecules can participate in the reaction through a proton transfer route, wherein the H2O molecules can build a high-speed proton transfer bridge between the generated moieties of CH3? and OH? over the evolved mono(μ-oxo) dicopper ([Cu-O-Cu]2+) active site, thereby pronouncedly boosting the CH3OH selectivity (3.1→71.6 %), productivity (16.8→242.9 μmol gcat?1 h?1) and long-term reaction stability (10→70 h) relative to the scenario of absence of H2O. Unravelling the proton transfer of H2O over the dicopper [Cu-O-Cu]2+ site would substantially contribute to highly efficient catalyst designs for the continuous DMTM.
- Chen, Biaohua,Dai, Chengna,Li, Yan,Liu, Ning,Wu, Bin,Xu, Ruinian,Yu, Gangqiang,Zhang, Jie
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supporting information
p. 16634 - 16640
(2021/06/23)
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- Morphology Effects of Nanoscale Er2O3 and Sr-Er2O3 Catalysts for Oxidative Coupling of Methane
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Abstract: Er2O3 nanorods were prepared by a hydrothermal method, and Sr-modified Er2O3 nanorods (Sr-Er2O3) were synthesized using an impregnation method. Their catalytic performance for oxidative coupling of methane was investigated. The catalysts were characterized by several techniques such as XRD, N2 adsorption, TEM, XPS, O2-TPD and CO2-TPD. Compared with Er2O3 and Sr-Er2O3 nanoparticles, Er2O3 and Sr-Er2O3 nanorods exhibit higher CH4 conversion and C2–C3 selectivity. This is caused by higher (O? + O2?)/O2? ratio, a higher number of chemisorbed oxygen species and moderate basic sites achieved on the nanorods catalysts. The Sr-Er2O3 nanorods afford a 23.2% conversion of CH4 with 50.3% selectivity to C2–C3 at 650?°C. Graphic Abstract: [Figure not available: see fulltext.]
- Fan, Yuqiao,Sun, Mingxing,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
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p. 2197 - 2206
(2021/01/04)
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- Oxidative coupling of methane over Mo-Sn catalysts
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A novel Mo-Sn catalyst for the oxidative coupling of methane was designed using a hydrothermal method. At 650 °C, the conversion of methane was 8.6% and the selectivity of the C2 hydrocarbons reached as high as 98.1% over the Mo1Sn3 catalyst, with a CO2 selectivity of only 0.8%. We demonstrated that the deep oxidation of methane to CO2 was further inhibited due to the synergistic effects of moderately strong basic sites and reactive oxygen species on the catalyst surface. This journal is
- Gao, Xiujuan,Han, Yizhuo,Liu, Xiaoyan,Meng, Xianghai,Song, Faen,Tan, Yisheng,Wang, Xiaoxing,Yan, Lina,Zhang, Junfeng,Zhang, Qingde,Zhang, Tao
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supporting information
p. 13297 - 13300
(2021/12/17)
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- New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na2WO4/SiO2 Catalysts
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The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na2WO4/SiO2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H2-TPR, TAP and steady-state kinetics) experiments, that the long speculated crystalline Na2WO4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na-WOx sites. Kinetic analysis via temporal analysis of products (TAP) and steady-state OCM reaction studies demonstrate that (i) surface Na-WOx sites are responsible for selectively activating CH4 to C2Hx and over-oxidizing CHy to CO and (ii) molten Na2WO4 phase is mainly responsible for over-oxidation of CH4 to CO2 and also assists in oxidative dehydrogenation of C2H6 to C2H4. These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na2WO4/SiO2 catalysts.
- Baltrusaitis, Jonas,Fushimi, Rebecca R.,Kiani, Daniyal,Sourav, Sagar,Wachs, Israel E.,Wang, Yixiao
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p. 21502 - 21511
(2021/08/25)
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- THERMAL OXIDATIVE COUPLING OF METHANE PROCESS USING RENEWABLE ENERGY WITH POSSIBLE CO-PRODUCTION OF HYDROGEN
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The disclosure relates in its first aspect to a process for converting methane into chemicals. The process comprises the steps of (a) providing a first stream (1; 7) comprising methane; (b) providing a second stream (13) which is an oxygen-rich stream; (c) contacting said first stream (1; 7) with said second stream (13) under oxidation reaction conditions to obtain a third stream (15) comprising chemicals and water; (d) performing at least one separation step on said third stream (15) to recover a water stream (21) and a fourth stream (39) comprising chemicals; (e) subjecting said water stream (21) to an oxidation reaction under first reaction conditions to produce at least an oxygen stream (29), wherein the oxygen stream (29) is recycled into the second stream (13). In its second aspect, the disclosure relates to an installation for working the process of the first aspect.
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Page/Page column 19
(2021/12/30)
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- Study on the selective oxidation of methane over highly dispersed molybdenum-incorporated KIT-6 catalysts
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A series of molybdenum-incorporated mesoporous silica (Mo-KIT-6) catalysts were successfully synthesized by a one-pot hydrothermal synthesis method, and were applied in the selective oxidation of methane to formaldehyde using oxygen as an oxidizing agent under atmospheric pressure. Comparatively, the corresponding supported catalysts (Mo/KIT-6) were prepared by incipient-wetness-impregnation method. The results of the small angle XRD, nitrogen adsorption/desorption isotherms, UV-vis, H2-TPR and UV-Raman spectroscopy characterization combined with the catalytic activity tests demonstrated that molybdenum atoms were inserted into the framework of the mesoporous materials for the Mo-KIT-6 catalysts and the highly dispersed MoO bonds dominantly existed, which were responsible for the efficient selective formation of formaldehyde. However, for Mo/KIT-6 catalysts, the molybdenum oxide species were mainly loaded on the surface or inside the outer pore channels of the support and abundant emergence of the Mo-O-Mo bond played a major role in the activation of methane to COx. Furthermore, with equivalent molybdenum content, the methane selective oxidation performance of 8Mo-KIT-6 was obviously better than that of 4.6Mo/KIT-6, and the formaldehyde yield (2.1%) of 8Mo-KIT-6 was 2.3 times as much as that (0.9%) of 4.6Mo/KIT-6.In situandoperandoUV-Raman results demonstrated that the structures of the MoOxactive sites have a strong effect on the formation and elimination of carbon deposition during the separated redox reaction with methane and O2, respectively. The polymerized MoOxactive sites are favorable for the formation of graphitic carbon (G), which is called ordered carbon, while the isolated MoOxactive sites are favorable for the formation of disordered carbon (D). The reduced highly dispersed MoOxactive sites incorporated in the framework of silica are more easily reoxidized than those on the supported catalysts.
- Chen, Pei,Fan, Xiaoqiang,Kong, Lian,Li, Jianmei,Liu, Baijun,Liu, Bonan,Xiao, Xia,Xie, Zean,Zhao, Zhen
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p. 4083 - 4097
(2021/06/30)
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- Iron phosphate nanoparticle catalyst for direct oxidation of methane into formaldehyde: Effect of surface redox and acid-base properties
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The effect of various iron phosphate and oxide catalysts on the direct oxidation of methane (CH4) to formaldehyde (HCHO) with molecular oxygen (O2) as the sole oxidant was studied using a fixed-bed flow reactor. Five crystalline iron-containing catalysts (FePO4, Fe3O3(PO4), Fe4(P2O7)3, Fe2P2O7, and α-Fe2O3) with different iron coordination geometries, iron oxidation states, and Fe/P ratios were synthesized by the sol-gel method using malic acid or aspartic acid. The Fe/P molar ratio had a significant effect on the oxidation catalysis; CH4 conversion increased with the Fe/P molar ratio, although the selectivity to HCHO decreased. Trigonal FePO4 nanoparticles synthesized by the malic acid-aided method with an Fe/P molar ratio of 1/1 exhibited the highest activity for the selective formation of HCHO among the catalysts tested, including FePO4 synthesized by a conventional method. Despite the much higher oxidizing ability of Fe2O3 than FePO4, the oxidation of CH4 using Fe2O3 resulted in the formation of only CO2. In contrast, the temperature-programmed reaction of FePO4 with CH4 gave Fe2P2O7 with the formation of HCHO as a primary product, and Fe2P2O7 reacted with O2 to regenerate FePO4. Based on mechanistic studies including the catalyst effect, kinetics, pulse-reaction experiments, and IR spectroscopy, the bulk structural change between FePO4 and Fe2P2O7 is not involved during the catalysis and the surface redox and acid-base properties of FePO4 are considered to play an important role in CH4 oxidation with the structure preservation of bulk FePO4. The combination of redox-active Lewis acidic iron sites and weakly-basic phosphate units likely contributes to the C-H activation of CH4 and the suppression of complete oxidation to CO2, respectively.
- Hara, Michikazu,Kamata, Keigo,Matsuda, Aoi,Tateno, Haruka
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p. 6987 - 6998
(2021/11/13)
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