7727-37-9Relevant articles and documents
Can TiO2 promote the reduction of nitrates in water?
Sa, Jacinto,Berger, Thomas,Foettinger, Karin,Riss, Alexander,Anderson, James A.,Vinek, Hannelore
, p. 282 - 291 (2005)
Monometallic palladium catalysts were synthesized using different titanium supports and tested for the reduction of nitrates from aqueous solutions using hydrogen as a reductant. The Pd/TiO2 catalysts were characterized by electron paramagnetic resonance (EPR), low-temperature Fourier transform infrared (FTIR) spectroscopy of adsorbed CO, and X-ray diffraction (XRD). The catalysts studied exhibited a high activity for nitrate removal with a lower tendency for nitrite formation than the conventional bimetallic Pd catalysts. Although ammonium formation was greater than desired, the use of a monometallic catalyst for this two-step reduction process is significant and suggests that a single site may be responsible for both reduction stages. The titanium support (particularly the Ti3+ centers generated during prereduction in the presence of Pd) appear to play an important role in the nitrate degradation process. The potential role of Pd β-hydride in generating these Ti 3+ centers is discussed.
Reaction between NOx and NH3 on Iron Oxide-Titanium Oxide Catalyst
Kato, Akira,Matsuda, Shimpei,Kamo, Tomoichi,Nakajima, Fumito,Kuroda, Hiroshi,Narita, Tsuneo
, p. 4099 - 4102 (1981)
The reduction of NOx (NO2 alone or mixture of NO and NO2) with NH3 on iron oxide-titanium oxide catalyst was studied using a flow reactor.The reaction between NO2 and NH3 proceeds at 3:4 mole ratio in the presence or absence of oxygen.When the reaction gas mixture contain equal amounts of NO and NO2, the reaction consuming equimolal NO and NO2 proceeds preferentially at a NH3/NOx ratio of unity.The rate of the reaction is faster than either the NO-NH3 or NO2-NH3 reaction.The overall reactions between NOx (NO2, NO+NO2) and NH3 are given as 6NO2+8NH3->7N2+12H2O and NO+NO2+2NH3->2N2+3H2O.Reaction mechanisms are proposed to explain the experimental results.
The 193 (and 248) nm photolysis of HN3: Formation and internal energy distributions of the NH (a1Δ, b1Σ+, A3Π, and c1Π) states
Rohrer, F.,Stuhl, F.
, p. 4788 - 4799 (1988)
The UV photolysis of HN3 at 193 nm was investigated in detail in the bulk phase at 300 K.NH radicals in the X, a, b, A, and c states were found to be formed with quantum yields 0.0019 , 0.4, 0.017, 0.00015, and 0.000 61, respectively.Relative rotational and vibrational populations were measured for all states except for NH(X).Average translational energies were estimated for NH(a,ν = 0 and 1 ) and NH(b,ν = 0).The 248 nm photolysis of HN3 was reinvestigated with respect to processes forming NH radicals other than NH(a).The observed energy distributions differ for both laser wavelengths and for high and low lying NH states.The distribution can be better described by a simple impulsive than by a statistical model.Some conclusions are drawn concerning the upper HN3 potential surfaces involved.
Oscillations in the N2O-H2 reaction over Ir(1 1 0). Route to chaos
Carabineiro, Sónia A.C.,Van Noort, Wibo D.,Nieuwenhuys, Bernard E.
, p. 96 - 102 (2003)
The study described in the present paper is focused on the N2O-H2 reaction on the Ir(1 1 0) surface and, in particular, on different kinds of oscillatory behaviour, including the route to chaos. Oscillations in rate were observed in the temperature range between 460 and 464 K, at a N2O pressure of 1 × 10-6 mbar with H2/N2O ratios close to 1. Upon minor changes in the H2/N2O ratio, a series of period doublings is observed, resulting finally in aperiodic behaviour.
Nano-spatially confined Pd-Cu bimetals in porous N-doped carbon as an electrocatalyst for selective denitrification
Bai, Nan,Chen, Zehan,Fan, Jianwei,Gu, Tianhang,Teng, Wei,Zhang, Wei-Xian,Zhao, Dongyuan
, p. 9545 - 9553 (2020)
Bimetals have attracted considerable attention as electrocatalysts towards selective reduction of nitrate to benign dinitrogen. Design of highly efficient and stable bimetallic catalysts by taking the effects of both active sites increasing and synergistic composition into account is of paramount importance but still a grand challenge. Herein we report novel bimetallic Pd-Cu nanoparticles (NPs) incorporated in porous N-doped carbon octahedra prepared by a spatial confinement strategy ofin situpyrolysis of metal-organic frameworks with the assistance of polyvinyl pyrrolidone (PVP) as electrocatalysts achieving targeted denitrification. Pd-Cu NPs exhibit superior dispersity with a N-doped matrix and are strongly dependent on the variation of PVP, Pd precursor and pyrolysis temperature. The material shows high efficiency (~97.1%) for the reduction of nitrate from 100 to 2.9 mg NO3--N L-1(well below drinking water standards of 10 mg NO3--N L-1), and especially the selectivity over 83% for benign N2at neutral pH within 24 h. Encapsulated and well-dispersed Pd-Cu NPs and doped N in the carbonaceous matrix synergistically enhance the interfacial electron transfer for transformation of NO3--N(v). Porous structures endow the catalyst with outstanding stability after eight cycles and over a wide pH of 4-10. More importantly, the nanocatalyst performs well with real contaminated water (selectivity of 91% for nitrogen) in laboratory batch reactors. This nanocatalyst shows promise in wastewater treatment and environmental remediation due to the spatial confinement strategy and introduction of heterogeneous atoms.
Promotional effects of Zr on K+-poisoning resistance of CeTiOx catalyst for selective catalytic reductionof NOx with NH3
Xu, Baoqiang,Xu, Haidi,Lin, Tao,Cao, Yi,Lan, Li,Li, Yuanshan,Feng, Xi,Gong, Maochu,Chen, Yaoqiang
, p. 1354 - 1361 (2016)
CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 (NH3-SCR). Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K+-poisoning resistance of the CeTiOx catalyst. The NH3-SCR performance of the catalysts showed that the NOx removal activity of the Zr-modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunauer-Emmett-Teller data indicated that the Zr-containing catalyst had a larger specific surface area and pore volume both before and after K+ poisoning. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X-ray photoelectron spectra showed that the Ce3+/Ce4+ ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K+ loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3-SCR performance; the temperature-programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K+-poisoning resistance of the CeTiOx catalyst.
MnO2-GO-scroll-TiO2-ITQ2 as a low-temperature NH3-SCR catalyst with a wide SO2-tolerance temperature range
Sun, Liwei,Zhang, Zeshu,Tian, Heyuan,Liu, Peng,Zhang, Yibo,Yang, Xiangguang
, p. 1733 - 1738 (2020)
Three steps are needed to improve the steam-resistance and SO2-resistance of a catalyst for the selective catalytic reduction of NOx through NH3 at low temperature: the first is to introduce a protective layer to reduce the direct contact between SO3 and the catalyst. Then, there is delayed oxidation, which fundamentally reduces the oxidation of SO2 to SO3. If the catalyst is used at a relatively high temperature, it will inevitably produce SO3. The third step is to add a strong acid site in addition to reducing the acidity of the catalyst, which first absorbs NH3 and then absorbs SO3, to seize NH4HSO4, so that it does not cover the active site. GO was used to curl and wrap around the outside of MnO2 nanowires as a protective layer. TiO2 was selectively deposited on oxygen-containing functional groups on GO, which delayed the oxidation ability of the catalyst. ITQ2 molecular sieves acted as strong acid sites to absorb NH4HSO4. The curling behavior of GO outside MnO2 nanowires, the deposition location of TiO2 and the distribution of ITQ2 were explained by morphology and elemental analysis. In the range of 150 °C to 280 °C, the MnO2-GO-scroll-TiO2-ITQ2 catalyst conversion of NO to N2 was more than 85%. Combined with H2-TPR and activity testing, the source of the wide SO2-tolerance temperature range of the catalyst was described in detail.
Enhanced NH3 Selective catalytic reduction for NO xAbatement
Forzatti, Pio,Nova, Isabella,Tronconi, Enrico
, p. 8366 - 8368 (2009)
Enhanced NO reduction efficiencies, close to those obtained under the conditions of fast selective catalytic reduction (SCR; see diagram), were achieved over commercial vanadium and ironexchanged zeolite SCR catalysts at low temperatures (200-300°C) in th
Promoting effects of Na and Fe impurities on the catalytic activity of CaO in the reduction of NO by CO and H2
Acke, Filip,Panas, Itai
, p. 5127 - 5134 (1998)
The heterogeneous reduction of NO by H2 and CO over different CaO materials is investigated. The dependence of the specific NO reduction rate on the impurity content is demonstrated for both reducing species. The roles of two specific impurities, i.e., Na and Fe, as well as their combined effect are investigated. The apparent activation energies for the NO + CO and NO + H2 reactions are determined for three different calcium oxides. Values between 26 and 28 kcal/mol are obtained. The influence of impurity content is found in the preexponential factor of the Arrhenius equation. A reaction mechanism based on a rate-determining surface-oxygen-abstraction step is suggested. This mechanistic understanding is explored to compare the activities of other alkaline-earth oxides. Particularly, a linear correlation between the apparent activation energy and the lattice parameter is observed.
Facile synthesis of Pd-Co-P ternary alloy network nanostructures and their enhanced electrocatalytic activity towards hydrazine oxidation
Zhang, Lu,Lu, Dingkun,Chen, Yu,Tang, Yawen,Lu, Tianhong
, p. 1252 - 1256 (2014)
Porous ternary Pd-Co-P alloy network nanostructures were synthesized by reducing K2PdCl4/K3Co(CN)6 cyanogel with a mixture of NaH2PO2 and NaBH4 at room temperature, which show superior electrocatalytic activity and stability towards hydrazine oxidation reaction.
Structural properties and photocatalytic activity of ceria nanoparticles on vermiculite matrix
Valá?ková, Marta,Kupková, Jana,Ko?í, Kamila,Ambro?ová, Nela,Klemm, Volker,Rafaja, David
, p. 7844 - 7848 (2016)
Clay mineral matrices and metal oxides are of current interest because of their high thermal stability, large surface area, and good catalytic and adsorption properties. Cerium oxide (ceria, CeO2) nanoparticles was obtained by interaction of ve
Anisotropy and Energy Disposal in the 193-nm N2O Photodissociation Measured by VUV Laser-Induced Fluorescence of O(1D)
Springsteen, L. L.,Satyapal, S.,Matsumi, Y.,Dobeck, L. M.,Houston, P. L.
, p. 7239 - 7241 (1993)
Laser induced fluorescence near 115 nm has been used to measure the Doppler profile of the O(1D) product of 193-nm N2O photolysis.The anisotropy of product recoil vectors is characterized by the paramter β = 0.50 +/- 0.05.The measured velocity distribution can be used to calculate a distribution of recoil energies that is in reasonable agreement with that reported recently by Felder, Haas, and Huber; an average of 27.3 kcal/mol is deposited into translation, leaving ca. 37 kcal/mol for the internal excitation of the N2 fragment.
Low-temperature hydrogen-selective catalytic reduction of NOx on Pt/sulfated-ZrO2 catalysts under excess oxygen conditions
Saito, Makoto,Itoh, Masahiro,Iwamoto, Jun,Machida, Ken-Ichi
, p. 1210 - 1211 (2008)
Platinum catalysts supported on sulfated zirconia powders highly promote the hydrogen-selective catalytic reduction (H2-SCR) of NOX at 100°C with formation of ammonia intermediate species derived from protons of the sulfonate groups
Kinetics, Kinetic Deuterium Isotope Effects, and Mechanism of Nitrous Oxide Reaction with Hydrogen on Supported Precious-Metal Catalysts
Miyamoto, Akira,Baba, Shigeo,Mori, Mitsushi,Murakami, Yuichi
, p. 3117 - 3122 (1981)
The kinetics and kinetic deuterium isotope effects have been precisely measured for the reaction of nitrous oxide with hydrogen on Ru/Al2O3, Rh/Al2O3, Ir/Al2O3, and Pt/Al2O3 catalysts.The reaction apparently proceeds through the two following elementary s
Synthesis of Complex Boron-Nitrogen Heterocycles Comprising Borylated Triazenes and Tetrazenes under Mild Conditions
Bélanger-Chabot, Guillaume,Braunschweig, Holger,Dietz, Maximilian,Guo, Xueying,Krummenacher, Ivo,Lin, Zhenyang,Müller, Marcel,Prieschl, Dominic
, p. 1065 - 1076 (2020)
The reactions of organic azides with diaryl(dihalo)diboranes(4) were explored, resulting in the observation of a number of surprising reactivity patterns. The reaction of phenyl azide with 1,2-diaryl-1,2-dihalodiboranes(4) resulted in the formation of five-membered rings comprising diboryl-triazenes with retention of the boron-boron bond, while the reaction of the peculiar 1,1-di(9-anthryl)-2,2-difluorodiborane(4) with phenyl azide yielded a six-membered ring bearing a diboryl-triazene, whereby the B-B bond was ruptured by the insertion of an arylnitrene-like reactive intermediate. Both types of heterocycles feature unprecedented connectivity patterns and are very rare examples of boryl triazenes beyond the more common 1,2,3-triazolatoboranes. They are also the product of a unique type of aryl migration from a boron center to the phenyl azide ?-nitrogen center. Lastly, the substitution of 1,2-diaryl-1,2-dihalodiboranes(4) with azide groups, using trimethylsilyl azide as the transfer reagent, yielded boryl-tetrazaboroles and diboryldiazadiboretidines (as side-products), invoking the intermediacy of the first N-boryl-substituted iminoboranes, which are BN isosteres of monoborylated alkynes. The synthetic results are complemented with mechanistic proposals derived from quantum-chemical calculations.
Fe-Ce-ZSM-5 a new catalyst of outstanding properties in the selective catalytic reduction of NO with NH3
Carja,Delahay,Signorile,Coq
, p. 1404 - 1405 (2004)
A Fe-Ce-ZSM-5 catalyst elaborated from a new synthesis route exhibits very high NO conversion (75-100%) in the selective catalytic reduction of NO by NH3 in a wide temperature window (523-823 K), even in the presence of H2O and SO2.
Oxygen photoevolution on a tantalum oxynitride photocatalyst under visible-light irradiation: How does water photooxidation proceed on a metal-oxynitride surface?
Nakamura, Ryuhei,Tanaka, Tomoaki,Nakato, Yoshihiro
, p. 8920 - 8927 (2005)
The mechanism of water photooxidation (oxygen photoevolution) on a TaON photocatalyst was studied on the basis of our previous studies on the mechanism of this reaction on TiO2 and N-doped TiO2. We have confirmed that photocatalytic O2 evolution occurs from an aqueous TaON suspension in the presence of Fe3+, as reported. In-situ MIR-IR experiments have indicated that the TaON surface is slightly oxidized under visible-light irradiation, indicating that the oxygen photoevolution on TaON actually occurs on a thin Ta-oxide overlayer. The in-situ MIR-IR experiments have also shown that a certain surface peroxo species, tentatively assigned to adsorbed HOOH, is formed as an intermediate of the O2 photoevolution reaction. Studies on the effect of addition of reductants to the electrolyte on the IPCE have shown that photogenerated holes at the TaON surface cannot oxidize reductants such as SCN-, Br-, methanol, ethanol, 2-propanol, and acetic acid, though they can oxidize H2O into O 2. Detailed considerations of these results have strongly suggested that the water photooxidation reaction on TaON proceeds by our recently proposed new mechanism, that is, the reaction is initiated by a nucleophilic attack of a water molecule (Lewis base) on a surface-trapped hole (Lewis acid). ? 2005 American Chemical Society.
Nickel-doped Mn/TiO2 as an efficient catalyst for the low-temperature SCR of NO with NH3: Catalytic evaluation and characterizations
Thirupathi, Boningari,Smirniotis, Panagiotis G.
, p. 74 - 83 (2012)
The Mn/TiO2 and a series of Mn-Ni/TiO2 catalysts were prepared by adopting incipient wetness technique and investigated for the low-temperature SCR of NO with NH3 in the presence of excess oxygen. Our XPS results illustrated that the MnO2 is the dominant phase with respect to the Mn2O3 phase (Mn4+/Mn 3+ = 22.31, 96%), thus leading to a large number of Mn4+ species (Mn4+/Ti) over the titania support for the Mn-Ni(0.4)/TiO2 catalyst. It is remarkable to note that the SCR performance of all the nickel-doped Mn/TiO2 catalysts is accurately associated with the surface Mn4+ concentrations. The co-doping of nickel into the Mn/TiO2 with 0.4 Ni/Mn atomic ratio promotes the formation of surface MnO2 phase and inhibits the formation of surface Mn2O3 sites. Our TPR results revealed that the addition of nickel oxide to titania-supported manganese results in the stabilization of the former in the form of MnO2 rather than Mn2O 3. Our TPR data results are in agreement with XPS results that the absence of the high-temperature (736 K) peak indicates that the dominant phase in the Mn-Ni/TiO2 catalysts is MnO2. The low-temperature reduction peak is shifted to much lower temperatures in nickel-doped Mn/TiO 2 catalysts. This increase in reducibility and the extremely dominant MnO2 phase seem to be the reason for the high SCR activity of the Mn-Ni/TiO2 catalysts.
Effect of postsynthesis preparation procedure on the state of copper in CuBEA zeolites and its catalytic properties in SCR of NO with NH3
Baran, Rafal,Averseng, Frederic,Wierzbicki, Dominik,Chalupka, Karolina,Krafft, Jean-Marc,Grzybek, Teresa,Dzwigaj, Stanislaw
, p. 332 - 342 (2016)
Copper-containing BEA zeolites, Cu2.0SiBEA and Cu2.0HAlBEA, with 2?wt% of Cu were prepared by a two-step postsynthesis method and a conventional wet impregnation, respectively. These zeolites were characterized by XRD, DR UV–vis, EPR, FTIR and TPR physicochemical techniques. The incorporation of Cu into framework of SiBEA was evidenced by XRD. The state of copper in both zeolites was investigated by DR UV–vis and EPR. The acidity of Cu2.0SiBEA and Cu2.0HAlBEA was determined by FTIR of adsorbed CO and pyridine. The reducibility of the Cu species present in both zeolites was studied by TPR and their catalytic properties were investigated in selective catalytic reduction of NO with NH3. Both Cu2.0SiBEA and Cu2.0HAlBEA zeolite catalysts showed very high activity in this reaction with the NO conversion higher than 80% and N2 selectivity higher than 95% in the temperature range between 473 and 623?K. The higher NO conversion and N2 selectivity in SCR of NO with ammonia at the high temperature range for the Cu2.0HAlBEA than for Cu2.0SiBEA suggest that the strong Br?nsted and Lewis acidic sites related to the framework and extra-framework aluminum atoms play an important role in SCR of NO process.
Obuchi, Akira,Naito, Shuichi,Onishi, Takaharu,Tamaru, Kenzi
, p. 29 - 40 (1983)
Meyer, L.
, p. 791 (1932)
Ruthenium-catalysed oxidative conversion of ammonia into dinitrogen
Nakajima, Kazunari,Toda, Hiroki,Sakata, Ken,Nishibayashi, Yoshiaki
, p. 702 - 709 (2019)
Conversion of ammonia into dinitrogen has attracted broad scientific interest in relation to molecular models of the heterogeneous nitrogen fixation process, environmental treatment for denitrification and utilization of ammonia as an energy carrier. Here we show that some ruthenium complexes bearing 2,2′-bipyridyl-6,6′-dicarboxylate ligands work as catalysts for the ammonia oxidation reaction. Production of dinitrogen is observed when ammonium salts are treated with a triarylaminium radical as an oxidant and 2,4,6-collidine as a base in the presence of the ruthenium catalysts. Based on the characterization of some intermediates, we propose a reaction pathway via a bimetallic nitride–nitride coupling process. The proposed reaction pathway is supported by density functional theory calculations. Further investigation of the ammonia oxidation reaction under the electrochemical conditions revealed that the ruthenium complex works as a new anode catalyst for ammonia oxidation.
In situ IR spectroscopic and XPS study of surface complexes and their transformations during ammonia oxidation to nitrous oxide over an Mn-Bi-O/α-Al2O3 catalyst
Slavinskaya,Chesalov,Boronin,Polukhina,Noskov
, p. 555 - 564 (2005)
Surface complexes resulting from the interaction between ammonia and a manganese-bismuth oxide catalyst were studied by IR spectroscopy and XPS. At the first stage, ammonia reacts with the catalyst to form the surface complexes [NH] and [NH2] via abstraction of hydrogen atoms even at room temperature. Bringing the catalyst into contact with flowing air at room temperature or with helium under heating results in further hydrogen abstraction and simultaneous formation of [N] from [NH2] and [NH]. The nitrogen atoms are localized on both reduced (Mn2+) and oxidized (Mn δ+, 2 δ+-N) active site. The nitrogen atoms localized on oxidized sites play the key role in N2O formation. Nitrous oxide is readily formed through the interaction between two Mnδ+-N species. N2 molecules result from the recombination of nitrogen atoms localized on reduced (Mn2+-N) sites.
Electron beam initiated discharges in HN3 gas mixtures
Schlie, L. A.,Wright, M. W.
, p. 394 - 400 (1990)
The behaviour of electron beam initiated discharges in HN3 and inert gas mixtures for different E/N values are presented.These results are the first reported investigations of this highly energetic azide gas under plasma conditions.Using a 3 ns. 600 KeV ionizing electron beam, the temporal decay of the discharge current shows HN3 is electronegative.HN3 attachment rate constants in Ar are 5.0-10.0x10-11 cm3 s-1 for E/N values in the range 1-4 Td (10-17 V cm2).With the other inert gases (He, Ne, Kr, and Xe), HN3 attachment rate constants are 0.5-4.5x10-10cm3 s-1 for the E/N range of 0.5-7.0 Td.Plasma excitation of Ar and HN3 gas mixtures produce intense N2(C -> B, υ' = 0 -> υ'' = 0) electronic transition radiation at 3371 Angstroem.
Measurement of heterogeneously catalyzed gas reactions by DSC
Hakvoort
, p. 445 - 452 (1996)
Gas reactions, catalyzed by solid catalysts, can be measured by DSC. In the experimental setup an open sample pan with catalyst (powder or pellet) is placed on the sample side of the DSC sensor. The reactive gas mixture flows through the cell and reacts on the catalyst surface. The heat effect, caused by this reaction, results into a DSC signal. The calibration procedure is described for quantitative evaluation of the DSC measurements. For illustration four different reaction systems are discussed.
Dual Nanoislands on Ni/C Hybrid Nanosheet Activate Superior Hydrazine Oxidation-Assisted High-Efficiency H2 Production
Li, Yapeng,Li, Ziyun,Liu, Yi,Qian, Qizhu,Xiao, Chong,Xie, Yi,Zhang, Genqiang,Zhang, Jihua,Zhu, Yin
supporting information, (2021/12/09)
Clean hydrogen evolution through electrochemical water splitting underpins various innovative approaches to the pursuit of sustainable energy conversion technologies, but it is blocked by the sluggish anodic oxygen evolution reaction (OER). The hydrazine oxidation reaction (HzOR) has been considered as one of the most promising substitute for OER to improve the efficiency of hydrogen evolution reaction (HER). Herein, we construct novel dual nanoislands on Ni/C hybrid nanosheet array: one kind of island represents the part of bare Ni particle surface, while the other stands for the part of core–shell Ni@C structure (denoted as Ni-C HNSA), in which exposed Ni atoms and Ni-decorated carbon shell perform as active sites for HzOR and HER respectively. As a result, when the current density reaches 10 mA cm?2, the working potentials are merely ?37 mV for HER and -20 mV for HzOR. A two-electrode electrolyzer exhibits superb activity that only requires an ultrasmall cell voltage of 0.14 V to achieve 50 mA cm?2.
Atomically Dispersed Copper Sites in a Metal-Organic Framework for Reduction of Nitrogen Dioxide
Chansai, Sarayute,Cheng, Yongqiang,Da Silva, Ivan,Haigh, Sarah J.,Han, Xue,Hardacre, Christopher,Lee, Daniel,Li, Weiyao,Ma, Yujie,Manuel, Pascal,McInnes, Eric J. L.,Nikiel, Marek,Ramirez-Cuesta, Anibal J.,Rudi?, Svemir,Schr?der, Martin,Sheveleva, Alena M.,Tuna, Floriana,Wang, Zi,Xu, Shaojun,Yang, Sihai,Zou, Yichao
supporting information, p. 10977 - 10985 (2021/08/03)
Metal-organic framework (MOF) materials provide an excellent platform to fabricate single-atom catalysts due to their structural diversity, intrinsic porosity, and designable functionality. However, the unambiguous identification of atomically dispersed metal sites and the elucidation of their role in catalysis are challenging due to limited methods of characterization and lack of direct structural information. Here, we report a comprehensive investigation of the structure and the role of atomically dispersed copper sites in UiO-66 for the catalytic reduction of NO2 at ambient temperature. The atomic dispersion of copper sites on UiO-66 is confirmed by high-angle annular dark-field scanning transmission electron microscopy, electron paramagnetic resonance spectroscopy, and inelastic neutron scattering, and their location is identified by neutron powder diffraction and solid-state nuclear magnetic resonance spectroscopy. The Cu/UiO-66 catalyst exhibits superior catalytic performance for the reduction of NO2 at 25 °C without the use of reductants. A selectivity of 88% for the formation of N2 at a 97% conversion of NO2 with a lifetime of >50 h and an unprecedented turnover frequency of 6.1 h-1 is achieved under nonthermal plasma activation. In situ and operando infrared, solid-state NMR, and EPR spectroscopy reveal the critical role of copper sites in the adsorption and activation of NO2 molecules, with the formation of {Cu(I)···NO} and {Cu···NO2} adducts promoting the conversion of NO2 to N2. This study will inspire the further design and study of new efficient single-atom catalysts for NO2 abatement via detailed unravelling of their role in catalysis.
Synthesis of Zeolitic Mo-Doped Vanadotungstates and Their Catalytic Activity for Low-Temperature NH3-SCR
Tao, Meilin,Ishikawa, Satoshi,Murayama, Toru,Inomata, Yusuke,Kamiyama, Akiho,Ueda, Wataru
supporting information, p. 5081 - 5086 (2021/04/09)
Mo was successfully introduced into a vanadotungstate (VT-1), which is a crystalline microporous zeolitic transition-metal oxide based on cubane clusters [W4O16]8- and VO2+ linkers (MoxW4-x. x: number of Mo in VT-1 unit cell determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES)). It was confirmed that W in the cubane units was substituted by Mo. The resulting materials showed higher microporosity compared with VT-1. The surface area and the micropore volume increased to 296 m2·g-1 and 0.097 cm3·g-1, respectively, for Mo0.6W3.4 compared with the those values for VT-1 (249 m2·g-1 and 0.078 cm3·g-1, respectively). The introduction of Mo changed the acid properties including the acid amount (VT-1: 1.06 mmol g-1, Mo0.6W3.4: 2.18 mmol·g-1) and its strength because of the changes of the chemical bonding in the framework structure. MoxW4-x showed substantial catalytic activity for the selective catalytic reduction of NO with NH3 (NH3-selective catalytic reduction (SCR)) at a temperature as low as 150 °C.
