- Synthesis of thermally stable χ-alumina by thermal decomposition of aluminum isopropoxide in toluene
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Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transf
- Mekasuwandumrong, Okorn,Kominami, Hiroshi,Praserthdam, Piyasan,Inoue, Masashi
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- Direct evidence of temperature variation within ceramic powder compact during pulse electric current sintering
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Pulse electric current sintering (PECS) is a powerful technique for the preparation of nanoceramics. However, the temperature distribution within the ceramic powder compact during PECS is not uniform. In the present study, aluminum hydroxide powder is used as an in situ temperature indicator to determine the temperature uniformity. The phase evolution within the powder compact is taken to estimate its temperature distribution. The temperature is highest near the top surface of the compact; it then reduces with increasing distance away from the top surface of the compact. The temperature variation can be significantly reduced by inserting a carbon paper in between graphite punches and graphite mold and also by reducing the heating rate.
- Zhang, Dongming,Zhang, Lianmeng,Guo, Jingkun,Tuan, Wei-Hsing
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- Effect of milling on the formation of nanocrystalline x-Al 2O3 from gibbsite
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Gibbsite (FG) with mean particle diameter (d50 = 3μm) was milled in an attrition mill for 12 and 24 h using alumina balls as grinding media and calcined at different temperatures in the range of 350°-600°C. The properties of the alumina obtained were determined by X-ray diffraction, N2 physisorption, thermogravimetric/ differential thermal analyses, and transmission electron microscopy.Without milling, the alumina obtained normally contained the mixed phases between γ- and x-phase alumina. On the other hand, high purity of nanocrystalline vphase alumina (100 wt%) can be produced by calcination of the 24-h milled FG at 600°C. The isothermal kinetics measurements revealed that the rate constant (κ) for phase transformation increased as the particle size of gibbsite decreased and the calculated activation energy for transformation from FG to alumina decreased from 20.6 to 14.7 and 6.8 kJ/mol after milling for 12 and 24 h, respectively. The physical properties of nanocrystalline x-alumina obtained by the calcination of milled FG were comparable to those produced by the solvothermal method. The present results offer a simple way to prepare a large amount of pure x-phase alumina for particular industrial applications.
- Chaitree, Wasu,Jiemsirilers, Sirithan,Mekasuwandumrong, Okorn,Praserthdam, Piyasan,Charinpanitkul, Tawatchai,Panpranotw, Joongjai
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- Experimental and ab initio infrared study of χ-, κ- and α-aluminas formed from gibbsite
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χ-, κ- and α-alumina phases formed by dehydration of micro-grained gibbsite between 773 and 1573 K are studied using infrared spectroscopy (IR). The structural transitions evidenced by X-ray diffraction (XRD) were interpreted by comparing IR measurements with ab initio simulations (except for the χ form whose complexity does not allow a reliable simulation). For each phase, IR spectrum presents specific bands corresponding to transverse optical (TO) modes of Al-O stretching and bending under 900 cm-1. The very complex χ phase, obtained at 773 K, provides a distinctive XRD pattern in contrast with the IR absorbance appearing as a broad structure extending between 200 and 900 cm-1 resembling the equivalent spectra for γ-alumina phase. κ-alumina is forming at 1173 K and its rich IR spectrum is in good qualitative agreement with ab initio simulations. This complexity reflects the large number of atoms in the κ-alumina unit cell and the wide range of internuclear distances as well as the various coordinances of both Al and O atoms. Ab initio simulations suggest that this form of transition alumina demonstrates a strong departure from the simple pattern observed for other transition alumina. At 1573 K, the stable α-Αl2?3 develops. Its IR spectra extends in a narrower energy range as compared to transition alumina and presents characteristics features similar to model α-Αl2?3{dot operator} Ab initio calculations show again a very good general agreement with the observed IR spectra for this phase. In addition, for both κ- and α-Αl2?3, extra modes, measured at high energy (above 790 cm-1 for κ and above 650 cm-1 for α), can originate from either remnant χ-alumina or from surface modes.
- Favaro,Boumaza,Roy,Ledion,Sattonnay,Brubach,Huntz,Tetot
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- Studies on the thermal reactions of aluminium oxides and hydroxides
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The gibbsite →χ-alumina decomposition (in air) and the χ-alumina →boehmite transformation (under hydrothermal conditions) were investigated isothermally. Reaction products were characterized by TG and X-ray diffraction. The rate of the gibbsite →χ-alumina
- Novak, C.,Pokol, G.,Tomor, K.,Koemives, J.,Gal, S.
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- PREPARATION OF ALUMINAS THE EFFECT OF HEAT TREATMENT ON THE PROPERTIES OF ALUMINA.
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Aluminum hydroxide was prepared by precipitation from aluminum nitrate solution with ammonia solution. Thermal decomposition of the solid hydroxide was studied by means of TG, DTG and DTA. The sample was thermally treated in the temperature interval betwe
- Al-Mashta,Al-Derzi,Al-Saadi,Al-Daghistani
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- Preparation and microstructural and textural characterization of single-phase aluminum oxides
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Conditions for the preparation of single-phase η-, -, and χ-aluminas were determined. The structures of η- and χ-aluminas were characterized. With the use of high-resolution electron microscopy, it was found that η-Al2O3 particles exhibited the most developed {111} face and consisted of coherently joined domains with a pronounced platelet shape. Planar defects in the (111) plane occurred in the η-Al2O3 particles. Microstructural differences between single-phase η-Al2O3 and γ-Al2O 3 with a defect spinel structure were revealed. It was found that the η-Al2O3, χ-Al2O3, and -Al2O3 oxides are characterized by uniformly porous structures with average pore diameters of 47, 55, and 110 A, respectively.
- Kul'ko,Ivanova,Litvak,Kryukova,Tsybulya
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- Synthesis of thermally stable micro spherical χ-alumina by thermal decomposition of aluminum isopropoxide in mineral oil
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Thermal decomposition of aluminum isopropoxide (AIP) in mineral oil at 250-300 °C over a 2 h duration results in χ-alumina powders having high thermal stability. The mechanism of the process involves the formation of amorphous complex before further decomposition takes place. Phase transformation of the obtained products was also investigated. It was found that χ-alumina synthesized by this method transformed directly to α-alumina at temperature higher than 1000 °C.
- Mekasuwandumrong, Okorn,Silveston, Peter L.,Praserthdam, Piyasan,Inoue, Masashi,Pavarajarn, Varong,Tanakulrungsank, Waraporn
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- Formation of the morphology of continuous-precipitation aluminum hydroxides in the course of industrial synthesis
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X-ray phase and differential thermal analyses were used to study in detail how the morphology of aluminum hydroxides changes in separate stages of the technological process. The assumption that two pseudoboehmite modifications differing in crystallite dim
- Lamberov,Aptikasheva,Egorova,Levin,Gil'manov
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- Mesostructured forms of the transition phases η- and χ-Al 2O3
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A surfactant-templated route to mesostructured forms of the transition alumina phases η-Al2O3 and χ-Al2O 3 is described. The surface areas and pore-size distributions of these novel forms of alumina are substantially improved with respect to those of conventional forms of these phases. Wormholelike pores are visible in the TEM image shown of mesostructured η-Al2O3. (Figure Presented).
- Zhang, Zhaorong,Pinnavaia, Thomas J.
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- On the decomposition of synthetic gibbsite studied by neutron thermodiffractometry
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The thermal decomposition mechanism of synthetic A1(OH)3 (gibbsite) was studied in situ by neutron thermodiffractometry in an ambient atmosphere from room temperature to 600°C with 50°C steps. Gibbsite decomposed to yield AIO · (OH) (boehmite) and then poorly crystallized Χ-Al2O3. Rietveld analysis was used to refine the cell parameters' variation of gibbsite and its thermal expansion coefficients were obtained: for the a-axis: 15±1×106 K-1, for b: 10±2×10-6 K-1, and for c: 17±2× 10-6 K-1.
- Mercury, Jose Manue Rivas,Pena, Pilar,De Aza, Antonio H.,Sheptyakov, Denis,Turrillas, Xavier
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- Optical, electrical and dielectric properties of mixed metal oxides derived from Mg-Al Layered Double Hydroxides based solid solution series
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In this work, we investigated the effect of aluminum content on optical, electrical and dielectric properties of mixed metal oxides (MMOs), obtained from calcination at 726 K of solid solution series based on nitrate intercalated Mg1-xAlx Layered Double Hydroxides (x = 0.167, 0.20, 0.25, 0.33). Subsequently, the MMOs were characterized by X-Ray Diffraction, and analyzed by Inductively Coupled Plasma, Scanning Electron Microscopy, Diffuse Reflectance Spectroscopy and Impedance Spectroscopy. It was found a shift of light absorption towards shorter wavelengths, and an increase of conductivity and dielectric constant when the aluminum content increased. Higher aluminum content exhibited strong ultraviolet light absorption with average band gap of 6.29 eV, and also manifested high reflectance in visible and near-infrared wavelengths, whereas lower aluminum content showed lower values of conductivity, dielectric constant and dielectric loss tangent. Moreover, the electrical, dielectric and optical parameters of MMOs were reported and discussed.
- Lahkale,Sadik,Elhatimi,Bouragba,Assekouri,Chouni,Rhalmi,Sabbar
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- Synthesis and luminescence properties of Eu2+/Ce3+, Ce3+/Tb3+ and Eu2+/Tb3+ co-doped AlONs
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Series of Eu2+/Ce3+, Ce3+/Tb3+ and Eu2+/Tb3+ co-doped aluminum oxynitrides Al5O6N were prepared using the standard sol-gel technique with following annealing in the flow of N2. In all the samples Al5O6N is a major phase, just traces of α-Al2O3 and AlN were found for some particular samples with high loading of rare-earth ions. According to pulsed cathodoluminescence and photoluminescence data a non-radiative energy transfer occurs from Ce3+ to Eu2+, from Ce3+ to Tb3+ and from Eu2+ to Tb3+. Also, it was shown that for Eu2+/Ce3+ co-doped Al5O6N the optimal contents of both REE ions are different compared to those for single doped Al5O6N (0.25 at% of Eu2+ and 0.04 at% of Ce3+). In case of Al5O6N:0.4%Tb3+,yCe3+ (y = 0.01…0.08%) the PCL and PL intensities increase in the whole range of Ce3+ content. Finally, for Al5O6N:0.4%Tb3+,yEu2+ (y = 0.1…0.8%) no pronounced dependence of luminescence caused by Tb3+ ions on the Eu2+ content is observed. Concentration quenching of Eu2+ caused luminescence is given at Eu2+ content above 0.3%. The chromaticity coordinates of prepared co-doped AlONs were calculated and three samples were found to give close to white emission.
- Akhmadullina, Nailya S.,Ishchenko, Aleksey V.,Kargin, Yury F.,Lysenkov, Anton S.,Shishilov, Oleg N.
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- Electroluminescent polycrystalline Er-doped Lu3Al5O12 nanofilms fabricated by atomic layer deposition on silicon
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The sub-nanometer composition and interlayer thicknesses of the silicon-based Lu2O3/Al2O3 nanolaminates are regulated by atomic layer deposition, to fabricate polycrystalline Er-doped Lu3Al5/sub
- Ma, Zhiqiang,Sun, Jiaming,Xu, Jing,Yang, Li,Yang, Yang
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- Influence of hydrothermal conditions on the phase transformations of amorphous alumina
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Amorphous Al2O3 transforms into the pseudoboehmite and boehmite phases of AlO(OH) under hydrothermal conditions. Specific surface area, pore volume and the amount of acidic sites decrease upon complete conversion of amorphous Al
- Egorova, Svetlana R.,Lamberov, Alexander A.,Mukhamed'yarova, Aliya N.,Nosova, Oksana V.
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p. 385 - 387
(2021/06/07)
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- Interesterification of triglycerides with methyl acetate for the co-production biodiesel and triacetin using hydrotalcite as a heterogenous base catalyst
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Biodiesel is a renewable fuel with several advantages over petro-based fuels and is conventionally produced by the transesterification of triglycerides with alcohols. Chemical interesterification of triglycerides is a good alternative as compared to transesterification, as it yields a value-added compound, triacetin, as a co-product instead of the already abundant commodity, glycerol. In this work, interesterification of soybean oil was carried out with methyl acetate to co-produce biodiesel and triacetin, using calcined hydrotalcite as a heterogeneous base catalyst. Several base catalysts were tested for this reaction. Calcined Mg-Al hydrotalcite (Mg:Al mole ratio – 3:1) was found as the best catalyst for achieving 95.9 % conversion of soybean oil triglycerides in 4 h and yielding 5.3 % selectivity of triacetin along with the value-added intermediates - monoacetindiglycerides and diacetinmonoglycerides, produced with a selectivity of 46 % and 48.7 %, respectively. The optimum reaction conditions were found at an oil to methyl acetate mole ratio of 1:50, catalyst loading of 0.04 g/cm3 and a temperature of 200 oC. The catalysts were fully characterized before and after the reaction, and were found to possess high surface area with both basic and acidic sites. The effect of various reaction conditions on the rate of reaction, conversion of triglycerides and selectivity of triacetin were studied. The concentration profiles of the reactants, intermediates and products obtained at different temperatures were used to obtain the kinetic rate constants and the activation energy of each parallel step was evaluated. Reusability studies showed that the catalyst was stable and reusable up to three cycles.
- Dhawan, Manali S.,Barton, Scott Calabrese,Yadav, Ganapati D.
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p. 101 - 111
(2020/08/21)
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- Production of liquid fuel intermediates from furfural via aldol condensation over La2O2CO3-ZnO-Al2O3 catalyst
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Aldol condensation of furfural with acetone over basic catalysts allows the production of furanic adducts 4-(2-furyl)-3-buten-2-one (FAc, C8) and 1,5-di-2-furanyl-1,4-pentadien-3-one (F2Ac, C13)) that can be transformed into high-quality diesel
- Fang, Zhen,Kong, Xiao,Lei, Hanwu,Li, Lu-ping,Wei, Xiao-jie
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- Synthesis and Thermal Degradation of MAl4(OH)12SO4·3H2O with M = Co2+, Ni2+, Cu2+, and Zn2+
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The synthesis and thermal degradation of MAl4(OH)12SO4·3H2O layered double hydroxides with M = Co2+, Ni2+, Cu2+, and Zn2+ ( MAl4-LDH ) were investigated by inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis, powder X-ray diffraction, Rietveld refinement, scanning electron microscopy, scanning tunnel electron microscopy, energy-dispersive X-ray spectroscopy, and solid-state 1H and 27Al NMR spectroscopy. Following extensive synthesis optimization, phase pure CoAl4- and NiAl4-LDH were obtained, whereas 10-12% unreacted bayerite (Al(OH)3) remained for the CuAl4-LDH. The optimum synthesis conditions are hydrothermal treatment at 120 °C for 14 days (NiAl4-LDH only 9 days) with MSO4(aq) concentrations of 1.4-2.8, 0.7-0.8, and 0.08 M for the CoAl4-, NiAl4-, and CuAl4-LDH, respectively. A pH ≈ 2 for the metal sulfate solutions is required to prevent the formation of byproducts, which were Ni(OH)2 and Cu3(SO4)(OH)4 for NiAl4- and CuAl4-LDH, respectively. The thermal degradation of the three MAl4-LDH and ZnAl4-LDH in a nitrogen atmosphere proceeds in three steps: (i) dehydration and dehydroxylation between 200 and 600 °C, (ii) loss of sulfate between 600 and 900 °C, and (iii) formation of the end products at 900-1200 °C. For CoAl4-LDH (ZnAl4-LDH), these are α-Al2O3 and CoAl2O4 (ZnAl2O4) spinel. For NiAl4-LDH, a spinel-like NiAl4O7 phase forms, whereas CuAl4-LDH degrades by a redox reaction yielding a diamagnetic CuAlO2 (delafossite structure) and α-Al2O3.
- Andersen, Anders B. A.,Hansen, Lars Pilsgaard,Henriksen, Christian,Nielsen, Ulla Gro,Ravnsb?k, Dorthe Bomholdt,Wang, Qian
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supporting information
p. 16700 - 16712
(2021/11/13)
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- Composition and Antithermal Quenching of Noninteger Stoichiometric Eu2+-Doped Na-β-Alumina with Cyan Emission for Near-UV WLEDs
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Phosphors with high quantum efficiency and thermal stability play a key role in improving the performance of phosphor-converted white light-emitting diodes (pc-WLEDs). A near-UV-pumped LED shows a great advantage due to its reduction of the negative effect of blue light on human health. In this work, we propose a series of near-UV excitable cyan-emitting Eu2+-activated phosphors with a nominal composition of Na2–2xAl11O17+a:xEu2+ (x = 0.01–0.40), which crystallize in a sodium β-alumina phase with a composition close to Na1.22Al11O17.11. An excess amount of the sodium carbonate raw material makes up the volatile Na during the high-temperature process. The noninteger stoichiometric composition promotes the rigidity of the crystal structure with a slight excess of Na insertion into layers between spinel blocks of the NaAl11O17 matrix. The nonequivalent substitution of Na+ by Eu2+ generates intrinsic defects acting as carrier traps. As a result, the phosphor with an optimal nominal composition Na1.6Al11O17+a:0.20Eu2+, under the excitation at 365 nm, shows an asymmetric cyan emission band at 468 nm with internal and external quantum efficiencies of 81.3 and 56.9%, respectively. Remarkably, the phosphor exhibits antithermal quenching within 200 °C. A pc-WLED with a high color rendering index (87.2) suggests great potential of the phosphor in pc-WLEDs. Therefore, a combination of a rigid structure and deep trap level is an effective way in exploring new phosphors with high quantum efficiency and thermal stability.
- Shi, Rou,Zhang, Xujian,Qiu, Zhongxian,Zhang, Jilin,Liao, Shuzhen,Zhou, Wenli,Xu, Xuhui,Yu, Liping,Lian, Shixun
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p. 19393 - 19401
(2021/12/17)
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- Spherical Mesoporous Metal Oxides with Tunable Orientation Enabled by Growth Kinetics Control
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Recent advances in spherical mesoporous metal oxides (SMMOs) have demonstrated their enormous potential in a large variety of research fields. However, a direct creation of these materials with precise control on their key shape features, particularly pore architectures, remains a major challenge as compared to the widely explored counterpart of silica. Here, using Al2O3 as an example, we identified that deposition kinetics in solution played an essential role in the construction of different SMMOs. Specifically, a controlled Al3+ precipitation is critical to maintaining the electrostatic interaction between the inorganic precursors and the molecular templates, thereby achieving a designable assembly of these two components toward uniform mesoporous Al2O3-based nanospheres. We demonstrated that such a synthesis strategy is not only able to precisely control the channel orientations from concentric to radial and dendritic, a synthesis capability impeded so far for SMMOs, but is readily applicable to other metal oxides. Our study showed that the growth-kinetics control is a simple but powerful synthesis protocol and opened up a multifunctional platform to achieve systematic design of SMMOs for their future applications.
- Zhang, Wei,Li, Bin,Sun, Yong-Gang,Cao, An-Min,Wan, Li-Jun
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supporting information
p. 17897 - 17902
(2020/11/02)
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- SBA materials as support of iridium catalyst for hydrogenation reactions
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This paper investigates the catalytic properties of SBA-3 and SBA-15 supported iridium catalysts. The produced catalysts (1 wt.% Ir) were tested for their performance in hydrogenation of toluene and the selective nitro group hydrogenation of ortho-chloron
- Kiderys, Angelika,Kot, Monika,Janiszewska, Ewa,Pietrowski, Mariusz,Yang, Chia-Min,Zieliński, Micha?
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p. 178 - 186
(2019/03/27)
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- Study on kinetics of the pyrolysis process of aluminum sulfate
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Using high aluminum gangue as a raw material, aluminum sulfate 18 hydrate was made by the sulfuric acid leaching method under certain conditions. The product was characterized using X-ray diffraction (XRD) analysis of the phases, x-ray-fluorescence (XRF) analysis of the aluminum and sulfur content and thermogravimetric analysis of the crystallized water [Al2(SO4)3·18H2O]. Change characteristics of the crystal form and morphology during pyrolysis of octadecahydrate aluminum sulfate were studied by thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC), differential thermogravimetry (DTG), XRD and scanning electron microscope (SEM). The theoretical basis for the preparation of metallurgical alumina from octadecahydrate aluminum sulfate was provided. According to the characteristics of the crystal structure change, the pyrolysis process of octadecahydrate aluminum sulfate can be separated into three stages. The first stage (dehydration stage 87–250 °C) had a weight loss rate of 40.5% and a loss of 15 water molecules; the weight loss rate of the second stage (dehydration stage 280–414 °C) was 8.1% with three water molecules lost; the weight loss rate of the third stage (decomposition stage 770–900 °C) was 36.1%, where three SO3 molecules were lost. The pyrolysis products were mainly Al2O3. The activation energies of the three reaction stages were calculated using the Coats-Redfern method as 90.02 kJ/mol, 205.74 kJ/mol and 284.40 kJ/mol, respectively.
- Zheng, Guangya,Xia, Jupei,Chen, Zhengjie,Yang, Jin,Liu, Chenglong
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p. 285 - 292
(2019/11/14)
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- Preparation of alumina with different precipitants for the gas phase dehydration of glycerol and their characterization by thermal analysis
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Mesoporous aluminas were prepared using different precipitants at different pH of precipitation and evaluated in the gas phase dehydration of glycerol. Samples were characterized by thermal analysis techniques (TGA, NH3-TPD and TPO), specific surface area measurements, XRD and SEM. The gas phase dehydration of glycerol was performed in a fixed bed quartz tubular reactor at 773?K using a 10% glycerol aqueous solution. Thermogravimetric analysis has revealed the temperature regions of decomposition for the prepared alumina catalyst precursors. The specific surface area and the crystallinity of the samples were dependent on both the pH and the used precipitating agent. Samples precipitated with NaOH presented higher density of acid sites than the samples prepared with Na2CO3, regardless of precipitation pH. The catalytic properties of the prepared aluminas are mainly related to the specific surface area and to acidic characteristics. Conversions of glycerol above 85% were obtained for all samples. The selectivity for glycerol dehydration was strongly related to the amount and strength of acid sites. The best result for dehydration was obtained for samples prepared with NaOH and precipitated at pH = 5. These results are related to the higher specific surface area, greater amount of acid sites and the higher ratio of weak acid sites. TPO revealed the amount of carbon deposited on the catalysts. Samples that showed higher carbon formation also showed a higher production of light olefins, indicating that the formation of carbon is related to the formation of these byproducts. NH3-TPD has shown the ratio of different acid sites on the surface of alumina samples that makes possible to estimate the correlation between the acidity and the catalytic properties.
- Lima, Dirleia S.,Perez-Lopez, Oscar W.
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p. 1387 - 1398
(2020/01/28)
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- Pt/Al2O3 coated with N-doped carbon as a highly selective and stable catalyst for catalytic hydrogenation of: P -chloronitrobenzene to p -chloroaniline
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Selective catalytic hydrogenation of p-chloronitrobenzene on Pt-based catalysts is a green and high-efficient way for p-chloroaniline production. However, supported monometallic Pt catalysts often exhibit undesirable p-chloroaniline selectivity. We herein reported supported Pt catalysts with N-doped carbon (NC) as an overcoating (Pt/Al2O3?NC) to overcome the disadvantage. Three Pt/Al2O3?NC catalysts with different NC coating amounts were prepared by in situ carbonization of an ionic liquid. For comparison, Al2O3 coated by NC and Pt/Al2O3 coated by SiO2 were also prepared. A combination characterization confirmed that the NC overcoating was successfully formed on Pt/Al2O3 surface and Pt particles were completely coated by NC layers when ion liquid amount increased to 25 μl per g catalyst. Due to the intimate contact of NC layers and Pt particles Pt-NC heterojunctions were effectively formed on the catalyst surface. For the catalytic hydrogenation of p-chloronitrobenzene, Pt/Al2O3?NC with 25 μl ionic liquid as the NC precursor exhibited 100% selectivity to p-chloroaniline at 100% conversion of p-chloronitrobenzene. A lower ionic liquid amount led to decreased selectivity to p-chloroaniline. Furthermore, no deactivation was observed on Pt/Al2O3?NC during 5 catalytic cycles. The findings in the study demonstrate that coating noble metal catalysts by N-doped carbon is a promising method to enhance the selectivity and stability for catalytic hydrogenation of p-chloronitrobenzene.
- Sun, Jingya,Tang, Yuqiong,Weng, Xin,Xu, Zhaoyi,Zheng, Shourong,Zhu, Donghong
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p. 14208 - 14216
(2020/04/23)
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- Thermodynamics and kinetics of the carbothermal reduction of aluminum sulfate
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The thermodynamic analysis and kinetics of the carbothermal reduction of aluminum sulfate using anthracite as the reducing agent are reported. The results showed that the reduction reaction was controlled by interfacial chemical reaction when the carbon e
- Zheng, Guangya,Xia, Jupei,Chen, Zhengjie
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- Study of the effect of Gd-doping ceria on the performance of Pt/GdCeO2/Al2O3 catalysts for the dry reforming of methane
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This work studied the performance of Pt/Al2O3 and Pt/CexGd1-xO2/Al2O3 catalysts for the dry reforming of methane at 1073 K. Pt/Al2O3 catalyst underwent seve
- da Fonseca,Garrido,Rabelo-Neto,Silveira,Sim?es,Mattos,Noronha
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p. 737 - 745
(2019/05/06)
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- Identification of Radiolytically-Active Thermal Transition Phases in Boehmite
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The stability of aluminum oxyhydroxide (AlOOH, boehmite) to radiolysis and dehydration to alumina (γ-Al2O3) under vacuum was investigated using TGA followed by detailed, structural analysis with Raman, powder X-Ray Diffraction (pXRD)
- Graham, Trent R.,Huestis, Patricia L.,LaVerne, Jay A.,Mergelsberg, Sebastian T.
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- A novel vapor-phase catalytic synthetic approach for industrial production of 1,1,1,3,3,3-hexafluoroisopropyl methylether
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1,1,1,3,3,3-Hexafluoroisopropylmethyl ether (HFE-356mmz) is an important substitute for chlorofluorocarbons and hydrochlorofluorocarbons due to its zero ozone depletion potential and low global warming potential. However, mass production of HFE-356mmz remains a long-standing challenge. Herein, we applied metal fluorides as catalysts in the methylation of 1,1,1,3,3,3-hexafluoroisopropanol to produce HFE-356mmz for the first time. The catalyst not only improves the synthetic efficiency, but also makes the reaction solvent-free. The pollution-free, recyclable, and continuous synthetic process enables industrial production of HFE-356mmz. To optimize the synthetic efficiency, a series of metal fluorides (AlF3, MgF2, CaF2, SrF2, and BaF2) was used, among which MgF2 exhibited the highest activity. Through careful examination of each metal fluoride, it was found that the activity of the catalyst was determined by co-operative action of the surface acid–base properties and the total amount of surface acid sites. Based on these results, a rational mechanism for the vapor-phase methylation was proposed.
- Li, Wei,Yang, Gang,Lu, Fengniu,Zhang, Xiaoling
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- Influence of the substitution pattern of four naphthalenedicarboxylic acids on the structures and properties of group 13 metal-organic frameworks and coordination polymers
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Metal-organic frameworks containing Ga3+ ions and four differently substituted naphthalenedicarboxylates (ndc2-) have been synthesized and characterized. The Ga3+ ions are six-fold coordinated by oxygen atoms in all title compounds, but two different inorganic building units, i.e. trans corner-sharing and cis,trans edge-sharing octahedra are observed. Crystal structures were validated by Rietveld refinements against powder X-ray diffraction data. [Ga(OH)(1,4-ndc)]·2H2O crystallizes in a non-breathing MIL-53 type structure with two different pore sizes (5.5 × 5.5 ? and 9 × 9 ?). It is non-porous with respect to nitrogen but has a water adsorption capacity of about 155 mg g-1 and a thermal stability of up to 240 °C. The dense compound [Ga(OH)(1,8-ndc)] crystallizes in a new layered structure motif, which is related to the crystal structure of MIL-122 ([Al(OH)((O2C)4C6H2)]). The third and fourth compounds [Ga2(OH)4(2,3-ndc)]·H2O and [Ga(OH)(2,6-ndc)]·H2O are isoreticular to CAU-15 ([Al2(OH)4(2,3-bdc)]·H2O) and MIL-69 ([Al(OH)(2,6-ndc)]·H2O), respectively. The last two compounds are non-porous toward nitrogen but reversible dehydration was demonstrated. For comparison, the two new compounds [Al(OH)(1,8-ndc)] and [Al2(OH)4(2,3-ndc)]·H2O, which are isostructural to the newly described gallium compounds, were also synthesized and fully characterized. The Al-containing coordination polymers exhibit higher temperature stabilities compared to their isostructural Ga compounds.
- Pewe, Harm,Rabe, Timo,Reinsch, Helge,Stock, Norbert,Svensson Grape, Erik,Willhammar, Tom
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supporting information
p. 4861 - 4868
(2020/04/24)
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- Effect of crystalline ordering on the luminescent properties of Eu3+-doped aluminum oxide nanophosphors
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Al2O3:Eu3+ nanophosphors were synthesized by the microwave assisted solvothermal technique. The structural and photoluminescence characteristics of alumina powders doped with 6.4 ?at.percent, 7.5 ?at.percent, 9.5 ?at.percent and 13 ?at.percent Eu, calcined at 900 ?°C, 1000 ?°C, 1100 ?°C and 1200 ?°C for 3 ?h, were investigated by X-ray diffraction, and reflectance, photoluminescent and X-ray fluorescence spectroscopies. The effects of the calcination temperature on the structure and, in turn of it on the photoluminescence properties are investigated. Luminescent decays curves were measured for the emission ascribed to the 5D0-7F2 transition in all the samples and a non-exponential behavior is observed. An increase in the average lifetime correlates well with the formation of the EuAlO3 perovskite phase as the calcination temperature increases. Judd-Ofelt analyses were performed and some additional quantities were derived from them such as the radiative and nonradiative transition rates and the emission quantum ef?ciency. The decrease in the Ω2 parameter value as the calcination temperature increases is compatible with a higher symmetry around the Eu3+ site as well as with a reduction in the Eu3+ covalence bonding within this ion into EuAlO3 perovskite.
- Aguilar-Frutis, M.,Alarcón-Flores, G.,Falcony, C.,González, F.,Padilla-Rosales, I.,Sosa, R.
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- Probing the limits of linker substitution in aluminum MOFs through water vapor sorption studies: mixed-MOFs instead of mixed-linker CAU-23 and MIL-160 materials
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We report a systematic study on the possibility of forming mixed-linker metal-organic frameworks (MOFs) spanning between the aluminum MOFs CAU-23 and MIL-160 with their 2,5-thiophenedicarboxylate (TDC) and 2,5-furandicarboxylate (FDC) linkers, respectively. The planned synthesis of a mixed-linker MOF, combining TDC and FDC in the framework turned out to yield a rather largely intricate mixture of CAU-23 and MIL-160. This is due to the different opening angles of 150° for TDCversus120° for FDC and the concomitantcis-trans versus cis-only OH-bridges in the infinite secondary building unit {Al(μ-OH)(O2C-)} chains. At the same time, the CAU-23 phase is accompanied by the polymorphic MIL-53-TDC phase withtrans-only OH-bridges. The measurement of water vapor sorption isotherms was the method of choice to confirm the formation of mixed MOFs instead of mixed-linker phases. Thereby, the water sorption isotherms indicate the simultaneous formation of both MOF phases, albeit they do not exclude mixed-linker MOFs which may have formed at low levels of substitution. The differentiationviapowder X-ray diffractometry (PXRD), IR-spectroscopy and nitrogen sorption was either not conclusive enough or impossible, due to similarities of the neat MOF phases. The synthesized MOF mixtures within the TDC?:?FDC ratios of 38?:?62 up to 82?:?18 exhibit two or three uptake steps in the water sorption isotherm, with the first two corresponding to an overlay from the individual water sorption isotherm of CAU-23 and MIL-160 and a third one from the additional MIL-53-TDC.
- Giesen, Beatriz,Janiak, Christoph,Jordan, Dustin Nils,Matemb Ma Ntep, Tobie J.,Schlüsener, Carsten,Schmitz, Alexa,Xhinovci, Mergime
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p. 7373 - 7383
(2020/06/21)
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- Synthesis of 1,3-Butadiene from 1-Butanol on a Porous Ceramic [Fe,Cr]/γ-Al2O3(K,Ce)/α-Al2O3 Catalytic Converter
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Abstract: —A two-stage method was developed for the synthesis of 1,3-butadiene by dehydration of 1-butanol to a mixture of butenes on γ-Al2O3 granules prepared by self-propagating high-temperature synthesis (SHS) followed by dehydrogenation of the butene fraction to 1,3-butadiene using a porous ceramic catalytic SHS converter [Fe,Cr]/γ-Al2O3(K,Ce)/α-Al2O3. The dehydration of 1-butanol to the butene mixture proceeded almost completely at ~100percent selectivity on γ-Al2O3 granules obtained by SHS at 300°C, which is 50 degrees lower than on industrial gamma-alumina granules. The use of an original hybrid catalytic membrane reactor (HCMR) with selective removal of hydrogen from the reaction zone led to a ~1.3-fold increase in the yield of 1,3-butadiene at ultrapure hydrogen extraction of up to 16 mol percent of the total amount of the hydrogen product. The catalytic activity of the system did not decrease after 20 h of experiment, in contrast to its activity in the industrial process, where catalyst regeneration is performed every 8–15 min.
- Dumeignil, F.,Fedotov, A. S.,Heyte, S.,Marinova, M.,Moiseev, I. I.,Paul, S.,Simon, P.,Tsodikov, M. V.,Uvarov, V. I.
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p. 390 - 404
(2020/07/03)
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- Droplet-oriented construction of porous metal oxide hollow microspheres and their assembly into superstructures
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Hollow porous materials with internal spaces or voids and highly porous structures have demonstrated desirable effectiveness in numerous areas. However, the traditional template methods for their synthesis are limited due to their sophisticated operations, expensive templates and low yield. Herein, with the aim to establish an efficient route for the scalable and low-cost production of hollow materials under mild conditions, we report a facile and versatile template-free strategy to prepare hollow porous metal oxide spheres with high specific surface areas, large pore volumes and abundant pores. The as-prepared NiO microspheres demonstrated a noteworthy surface area of 351 m2 g-1 and large pore volume of 0.55 mL g-1. The features of the preparation were based on spray technology and wet chemical methods. Moreover, we demonstrated the construction pathway and the possible formation mechanism of these hollow superstructures. The regulation of the shell thickness of the hollow microspheres was explored. Moreover, a series of hierarchical architectures and multicomponent hollow materials (e.g., MgO/Al2O3) was also designed and investigated. This journal is
- Zhu, Peihan,Tian, Peng,Gao, Tingting,Pang, Hongchang,Ye, Junwei,Ning, Guiling
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p. 12978 - 12984
(2020/08/24)
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- Synthesis, Crystal Structures, and Thermolysis Studies of Heteronuclear Transition Metal Aluminum Alcoholates
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Heteronuclear alcoholate complexes [M{Al(OiPr)4}2(bipy)] (2-M, M = Fe, Co, Ni, Cu, Zn) and [M{Al(OcHex)4}2(bipy)] (3-M, M = Fe, Co, Ni, Zn) are formed by adduct formation of [M{Al(OiPr)4}2] (1-M, M = Fe, Co, Ni, Cu, Zn) with 2,2'-bipyridine and transesterification reaction with cHexOAc. According to crystal structure analyses, in 2-M and 3-M the central transition metal ion M2+ is coordinated by two chelating Al(OR)4– moieties and one bipyridine ligand in an octahedral arrangement. Treating 1-Cu with 2,2'-bipyridine leads to a reduction process, whereat the intermediate [Cu{Al(OiPr)4}(bipy)2][Al(OiPr)4] (4) could be structurally characterized. During conversion of the iso-propanolate ligands in 1-Cu to cyclohexanolate ligands, Cu2+ is reduced to Cu+ forming [Cu{Al(OcHex)4}(py)2] (5). UV/Vis-spectra and results of thermolysis studies by TG/DTA-MS are reported.
- Küsel, Sebastian,Krautscheid, Harald
-
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- Esterification of Tertiary Amides by Alcohols Through C?N Bond Cleavage over CeO2
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CeO2 has been found to promote ester forming alcoholysis reactions of tertiary amides. The present catalytic system is operationally simple, recyclable, and it does not require additives. The esterification process displays a wide substrate scope (>45 examples; up to 93 % isolated yield). Results of a density functional theory (DFT) study combined with in situ FT-IR observations indicate that the process proceeds through rate limiting addition of a CeO2 lattice oxygen to the carbonyl group of the adsorbed acetamide species with energy barrier of 17.0 kcal/mol. This value matches well with experimental value (17.9 kcal/mol) obtained from analysis of the Arrhenius plot. Further studies by in situ FT-IR and temperature programmed desorption using probe molecules demonstrate that both acidic and basic properties are important, and consequently, CeO2 showed the best performance for the C?N bond cleavage reaction.
- Toyao, Takashi,Nurnobi Rashed, Md.,Morita, Yoshitsugu,Kamachi, Takashi,Hakim Siddiki,Ali, Md. A.,Touchy,Kon, Kenichi,Maeno, Zen,Yoshizawa, Kazunari,Shimizu, Ken-ichi
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p. 449 - 456
(2018/09/11)
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- Controlled grafting of dialkylphosphonate-based ionic liquids on γ-alumina: Design of hybrid materials with high potential for CO2 separation applications
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In this work we provide a detailed study on grafting reactions of various dialkylphosphonate-based ILs. Special attention has been devoted to a comprehensive investigation on how the nature of the anion and the organic spacer composition (hydrophilic or hydrophobic groups) could impact the grafting densities and bonding modes of phosphonate-based ILs anchored to γ-alumina (γ-Al2O3) powders. For the first time, the bonding of phosphonate-based ILs with only surface hexacoordinated aluminum nuclei was established using both solid-state 31P-27Al D-HMQC and 31P NMR experiments. It has been demonstrated that the grafting of dialkylphosphonate-based ILs is competing with a hydrolysis and/or precipitation process which could be attractively hindered by changing the anion nature: bis(trifluoromethane)sulfonylimide anion instead of bromide. In additon, independently of the chosen spacer, similar reaction conditions led to equivalent grafting densities with different bonding mode configurations. The CO2 physisorption analysis on both pure ILs and grafted ILs on alumina powders confirmed that the initial sorption properties of ILs do not change upon grafting, thus confirming the attractive potential of as-grafted ILs for the preparation of hybrid materials in a form of selective adsorbers or membranes for CO2 separation applications.
- Pizzoccaro-Zilamy,Pi?a, S. Mu?oz,Rebiere,Daniel,Farrusseng,Drobek,Silly,Julbe,Guerrero
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p. 19882 - 19894
(2019/07/10)
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- Preparation of Ni based mesoporous Al2O3 catalyst with enhanced CO2 methanation performance
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A Ni based mesoporous γ-Al2O3 (MA) catalyst was prepared via partial hydrolysis without organic surfactants and employed in the carbon dioxide methanation reaction. The obtained catalysts were characterized by N2 adsorption-desorption, H2-TPR, XRD, XPS, TG, SEM and TEM-EDS techniques. CO2 methanation was performed in a fixed-bed reactor. A high surface area of MA with excellent hydrothermal stability was obtained, which promoted the dispersion of nickel species, producing a better catalytic performance. Incorporation of more NiO species into the Ni/MA catalyst increased the amount of active metallic Ni sties, further improving the catalytic activity and CH4 selectivity. Moreover, the monolithic skeleton of MA with fabric-like walls suppressed the aggregation of active metallic Ni sites and carbon deposition, enhancing the catalyst's stability, which provides a new insight for potential industrial applications.
- Lin, Jianghui,Ma, Caiping,Luo, Jing,Kong, Xianghui,Xu, Yanfei,Ma, Guangyuan,Wang, Jie,Zhang, Chenghua,Li, Zhengfeng,Ding, Mingyue
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p. 8684 - 8694
(2019/03/21)
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- Highly effective transformation of methyl phenyl carbonate to diphenyl carbonate with recyclable Pb nanocatalyst
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Diphenyl carbonate (DPC) is a type of versatile industrial chemical, and the disproportionation of methyl phenyl carbonate (MPC) is a key step to produce DPC. However, the design and formulation of a catalyst for the efficient synthesis of DPC is a major challenge due to its small equilibrium constant. The support material is a critical factor influencing the performance of Pb nanocatalysts. Thus, a series of Pb-based catalysts over MgO, ZrO2, SiO2, TiO2 and Al2O3 were prepared to investigate the effect of the support materials on the physicochemical properties and catalytic performances for the conversion of MPC to effectively synthesize DPC. The catalysts were well characterized by XRD, BET, TEM, XPS, ICP-OES, H2-TPR, Py-IR and NH3-TPD. The results showed that the nature of the support obviously affected the structural properties and catalytic performances, and Pb was dispersed better on SiO2, TiO2, ZrO2 and MgO than on Al2O3, and showed stronger metal-support interaction over MgO and ZrO2. The activity results revealed that PbO/MgO and PbO/ZrO2 exhibited higher catalytic activities because they contained higher Pb dispersion and more Lewis acid sites, and the catalytic activities followed the order PbO/MgO > PbO/ZrO2 > PbO/SiO2 > PbO/Al2O3 > PbO/TiO2. On the contrary, PbO/MgO and PbO/ZrO2 exhibited better reusability due to strong interaction between the highly dispersed Pb and the supports, and the activity decrease in the case of PbO/SiO2, PbO/Al2O3 and PbO/TiO2 mainly resulted from the Pb leaching loss. This work would contribute to exploiting novel catalytic materials in a wide range of applications for the efficient synthesis of organic carbonates.
- Wang, Songlin,Niu, Hongying,Wang, Jianji,Chen, Tong,Wang, Gongying,Zhang, Jiamin
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p. 20415 - 20423
(2019/07/09)
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- Catalytic activity of rare earth and alkali metal promoted (Ce, La, Mg, K) Ni/Al2O3 nanocatalysts in reverse water gas shift reaction
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Abstract: Nanocrystalline Ni/Al2O3 catalysts and promoted Ni-M/Al2O3 (M = Ce, La, Mg, K) catalysts were employed a in reverse water gas shift reaction. Among the prepared nickel catalysts 5% Ni/Al2O3 catalyst showed high CO2 conversion and CO selectivity. To improve the CO2 conversion and CO selectivity of 5% Ni/Al2O3, 1 or 2?wt% Ce, La, Mg or K were used. One percent La and 2% K showed highest CO2 conversion and CO selectivity. The high activity and CO selectivity of promoted catalysts can be accredited to the increase of Ni dispersion (or smaller Ni particles), concentration of surface active sites and CO2 adsorption by basic nature of promoters. The prepared samples were characterized by X-ray diffraction, inductively coupled plasma emission spectroscopy, N2 adsorption–desorption (BET), temperature programmed reduction (TPR), scanning electron microscopy and transmission electron microscopy (TEM) techniques. The BET surface area of prepared γ-alumina support was 126.81?m2?g?1, impregnation of the support with Ni and promotion of 5?wt% Ni with K and La reduced the specific surface area. The support and catalysts possessed mesoporous structure. The TPR-H2 analysis revealed higher Ni dispersion and reducibility for promoted nickel catalysts; 5Ni–2K showed highest reducibility. TEM images of 5Ni and 5Ni–2K showed increase of Ni dispersion and decrease of Ni particle size for the promoted catalyst. After 50?h on stream at 600?°C, 5Ni–1La and 5Ni–2K performed great catalytic stability. Graphic abstract: [Figure not available: see fulltext.].
- Ranjbar, Atieh,Irankhah, Abdullah,Aghamiri, Seyed Foad
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p. 5125 - 5141
(2019/07/04)
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- Synthesis, Structural Characteristics, and Adsorption Properties of Macroporous Alumina
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Abstract: Macroporous alumina is synthesized via precipitation with sulfuric acid from a sodium aluminate solution. It is established that introducing a coagulating agent (sodium chloride) preventing macrogel formation makes it possible to obtain highly porous samples of alumina with specific surface areas of ~100 m2/g, a large pore volume of 1.6–1.7 cm3/g, and an average pore diameter of 50–75 nm. According to the adsorption isotherms and the pH dependence of hemoglobin adsorption that such samples have a high capacity for protein macromolecules. The maximum adsorption of hemoglobin is ~500 mg/g, and is observed at pH 6–7. Adsorption falls substantially when the pH is reduced to 4 or increased to 9, and it is close to zero at?pH?11.
- Khokhlova
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p. 1589 - 1591
(2019/08/16)
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- Self-assembled membrane manufactured by metal-organic framework (UiO-66) coated γ-Al2O3 for cleaning oily seawater
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In order to effectively clean oily seawater with anionic polyacrylamide (APAM), UiO-66 coated γ-Al2O3 (UA) composites were firstly synthesized using γ-Al2O3 as a template to induce the growth of high hydrophilic UiO-66 on its surface to form a uniform UA self-assembled membrane. The UA composites and self-assembled membrane were characterized and analyzed. Also, the membrane performance was investigated. The results show that the hydrophilicity of particles is enhanced with the water contact angle decreasing from 39.8° (γ-Al2O3 particles) to 26.2° (UA composites) by introducing the UiO-66 coating. Moreover, the UA self-assembled membrane performs attractive water yield and separation performance. The oil concentration in the permeate treated by the first class of UA self-assembled membrane declines apparently from 91.22 to 18.90 mg L-1, while the water yield is as high as 657.89 L m-2 h-1. The reclaimed separation experiments show that the membrane materials could be recycled by calcination at 200 °C and hydraulic cleaning, which gives the material potential application in cleaning oily seawater.
- Li, Cunlong,Zhang, Yuqing,Yong, Ming,Liu, Wei,Wang, Jiaqi
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p. 10702 - 10714
(2019/04/17)
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- Highly efficient hydrogenation of levulinic acid into 2-methyltetrahydrofuran over Ni-Cu/Al2O3-ZrO2 bifunctional catalysts
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Transformation of biomass or biomass-based feedstocks into fuels or valuable chemicals is of great importance for the sustainable development of our society. Mesoporous Al2O3-ZrO2 with different Al:Zr molar ratios was prepared by the sol-gel method, and Cu-Ni/Al2O3-ZrO2 catalysts were fabricated by the impregnation method. The catalytic performances of the bifunctional catalysts were studied in the selective hydrogenation of levulinic acid (LA) into 2-methyltetrahydrofuran (MTHF). It was demonstrated that both Cu:Ni and Al:Zr ratios affected the selectivity to MTHF significantly. The bimetallic catalysts Cu-Ni/Al2O3-ZrO2 containing 10 wt% Ni and 10 wt% Cu gave 99.8% MTHF selectivity at full conversion of LA when the Al:Zr ratio was 9:1. The outstanding catalytic performance of the catalyst is related to the mesoporous structure, the acidic properties of the support and the synergistic effect between Cu and Ni. The catalyst could be reused five times without a considerable loss of catalytic activity and selectivity.
- Xie, Zhenbing,Chen, Bingfeng,Wu, Haoran,Liu, Mingyang,Liu, Huizhen,Zhang, Jianling,Yang, Guanying,Han, Buxing
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p. 606 - 613
(2019/02/14)
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- Significant Decrease in Activation Temperature for the Generation of Strong Basicity: A Strategy of Endowing Supports with Reducibility
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Mesoporous solid strong bases are quite attractive due to their good catalytic performance for applications as environmentally friendly catalysts in various reactions. However, pretty harsh conditions are usually compulsory for the fabrication of strong basicity by using traditional thermal activation (e.g., 700 °C for the activation of base precursor KNO3 supported on mesoporous Al2O3). This is energy intensive and harmful to the mesoporous structure. In this study, we report a strategy of endowing supports with reducibility (ESWR) by doping low-valence Cr3+ into mesoporous Al2O3, so that the activation temperature for basicity generation is decreased significantly. Fascinatingly, KNO3 on mesoporous Al2O3 can be motivated to basic sites completely at the temperature of 400 °C via the ESWR strategy, which is much lower than the conventional thermal activation (700 °C). We have demonstrated that the redox reciprocity between KNO3 and Cr3+ is responsible for the lowerature conversion, and Cr6+ is formed quantitatively as the oxidation product. The obtained solid bases possessing ordered mesostructure and strong basicity provide promising candidates for base-catalyzed synthesis of dimethyl carbonate via transesterification. The catalytic activity is obviously higher than a typical solid base like MgO as well as a series of reported basic catalysts containing alkali metal and alkaline-earth metal oxides.
- Peng, Song-Song,Lu, Jie,Li, Tian-Tian,Tan, Peng,Gu, Chen,Wu, Zheng-Ying,Liu, Xiao-Qin,Sun, Lin-Bing
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p. 8003 - 8011
(2019/06/17)
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- Fabrication of solid strong bases at decreased temperature by doping low-valence Cr3+ into supports
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Mesoporous solid strong bases (MSSBs) have gained tremendous research interest as environment-friendly catalysts in various reactions. Nevertheless, the fabrication of MSSBs remains an enormous challenge because a pretty high temperature is needed to produce strong basicity in traditional mesoporous materials. Here, we report a strategy of endowing supports with reducibility (ESWR) by doping low-valence Cr3+ into mesoporous Al2O3. The base precursors NaNO3 can be converted to basic sites completely at the low temperature of 400 °C via the ESWR strategy. The examination of activation mechanism indicates that the redox interaction between Cr3+ and NaNO3 is responsible for the low-temperature conversion of supported NaNO3. As a result, MSSBs were synthesized successfully by the ESWR strategy, showing strong basicity and remarkable catalytic activity in the transesterification reaction. The catalytic activity is obviously higher than typical solid bases like MgO as well as a variety of reported basic catalysts.
- Peng, Song-Song,Wu, Ju-Kang,Peng, An-Zhong,Li, Yu-Xia,Gu, Chen,Yue, Ming-Bo,Liu, Xiao-Qin,Sun, Lin-Bing
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- The impact of an isoreticular expansion strategy on the performance of iodine catalysts supported in multivariate zirconium and aluminum metal-organic frameworks
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Iodine functionalized variants of DUT-5 (Al) and UiO-67 (Zr) were prepared as expanded-pore analogues of MIL-53 (Al) and UiO-67 (Zr). They were prepared using a combination of multivariate and isorecticular expansion strategies. Multivariate MOFs with a 25% iodine-containing linker was chosen to achieve an ideal balance between a high density of catalytic sites and sufficient space for efficient diffusion. Changes to the oxidation potential of the catalyst as a result of the pore-expansion strategy led to a decrease in activity with electron rich substrates. On the other hand, these larger frameworks proved to be more efficient catalysts for substrates with higher oxidation potentials. Recyclability tests for these larger MOFs showed sustained catalytic activity over multiple recycles.
- Tahmouresilerd, Babak,Moody, Michael,Agogo, Louis,Cozzolino, Anthony F.
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p. 6445 - 6454
(2019/05/24)
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- Kinetics of the topochemical reaction of the solid solutions of magnesia spinels: Mg(Cr0.5Fe0.5)2O4, Mg(Al0.5Cr0.5)2O4, Mg(Al0.5Fe0.5)2O4 with sulphur oxides
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Spinel-containing materials belong to an important group of refractories used as high-temperature unit linings. A crucial element of the conditions in which they are used is gaseous corrosion caused by sulphur oxides: SO2 and SO3. In previous investigations into reactions of magnesia spinels with sulphur oxides it was found that spinels’ reactivity could be considerably influenced by a phase transition (order – disorder) in the cation sublattice, resulting in a change of their reactivity in relation to SO2/SO3. The aim of the study was to investigate the kinetics of topochemical reactions between equimolar solid solutions of magnesia spinels and sulphur oxides before and after the order – disorder phase transformation in the structure begins. Research into the reaction of equimolar solid solutions Mg(Cr0.5Fe0.5)2O4, Mg(Al0.5Cr0.5)2O4, Mg(Al0.5Fe0.5)2O4 with SO3 was undertaken due to the fact that spinels form solid solutions in basic refractories. To conduct kinetic measurements, a semi-flow reactor was designed and constructed, in which investigations were carried out at the temperatures of 773 and 973 K and time range: 0–7 h. A mixture of air and SO2 (13%) was used. The obtained results have been compared with the kinetic results from the previous work obtained on two-cation spinels: MgAl2O4, MgFe2O4, MgCr2O4. The influence of the degree of inversion in spinel structure on the kinetics of the process was discussed.
- Gerle, Anna,Piotrowski, Jerzy,Podwórny, Jacek
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- Selective cleavage of lignin and lignin model compounds without external hydrogen, catalyzed by heterogeneous nickel catalysts
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Selective hydrogenolysis of the Caryl-O bonds in lignin is a key strategy for the generation of fuels and chemical feedstocks from biomass. Currently, hydrogenolysis has been mainly conducted using hydrogen, which is flammable and not sustainable or economical. Herein, an external hydrogen-free process for aryl ethers hydrogenolysis in lignin models and dioxasolv lignin over nickel nanoparticles supported on Al2O3, is reported. Kinetic studies reveal that the transfer hydrogenolysis activity of the three model compounds decreased in the following order: benzyl phenyl ether (α-O-4), 2-phenylethyl phenyl ether (β-O-4) and diphenyl ether (4-O-5), which linearly corresponds to their binding energies and the activation energies. The main reaction route for the three model compounds was the cleavage of the ether bonds to produce aromatic alkanes and phenol, and the latter was further reduced to cyclohexanol. Dioxasolv lignin depolymerization results exhibit a significant Caryl-O decrease over the Ni nanoparticles supported on Al2O3 with iso-propanol as the hydrogen source through 2D-HSQC-NMR analysis, which confirmed the transfer hydrogenolysis conclusion in the model study. This work provides an economical and environmentally-friendly method for the selective cleavage of lignin and lignin model compounds into value-added chemicals.
- Jiang, Liang,Guo, Haiwei,Li, Changzhi,Zhou, Peng,Zhang, Zehui
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p. 4458 - 4468
(2019/04/29)
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- A porous and redox active ferrocenedicarboxylic acid based aluminium MOF with a MIL-53 architecture
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A metallocene based linker 1,1′-ferrocenedicarboxylic acid (H2FcDC) was used to synthesise the first permanently porous ferrocenedicarboxylate, exhibiting a MIL-53 architecture. This compound Al-MIL-53-FcDC [Al(OH)(FcDC)] is obtained in glass v
- Benecke, Jannik,Mangelsen, Sebastian,Engesser, Tobias A.,Weyrich, Thomas,Junge, Jannik,Stock, Norbert,Reinsch, Helge
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supporting information
p. 16737 - 16743
(2019/11/19)
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- Recent progress in the biomass-mediated synthesis of porous materials
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The aim of this Account article is to demonstrate the versatility of using biomass residues or their extracted molecules in the synthesis of different families of porous materials. While our former studies mainly focused on zeolites, the present contribution gives more space to polyoxometalates (POMs), layered-doubled hydroxides (LDHs) as well as transitional mesoporous aluminas. The Bio-Sourced Secondary Template (BSST) strategy presented herein should serve as a basis for rationally preparing porous materials (micro-, meso- or macro- or combination of those) for sorption or catalytic applications.
- Bingre, Rogeria,Sayago, Cristina Megias,Losch, Pit,Huang, Liang,Wang, Qiang,Pereira, Marcelo M.,Louis, Beno?t
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p. 379 - 386
(2019/01/04)
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- Catalytic deoxygenation of C18 fatty acid over supported metal Ni catalysts promoted by the basic sites of ZnAl2O4 spinel phase
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Highly active Zn-Al composite oxides were synthesized via a hydrothermal process followed by thermal treatment and were used as supports to prepare Ni-based hydrogenation catalysts for catalytic deoxygenation of oleic acid, stearic acid, and 1-octadecanol. The results showed that increasing the temperature of hydrothermal synthesis changed the morphology of the Zn-Al composite oxides from sheet-like structures to spheroidal structures. High hydrothermal synthesis temperatures enhanced the interaction between Zn and Al atoms, resulting in more ZnAl2O4 spinel phase. This phase not only improved the chemical stability of the support but also supplied strong basic sites which efficiently inhibited the formation of by-products and increased the yield of heptadecane in the catalytic deoxygenation of oleic acid. Stearic acid and 1-octadecanol could be readily transformed to alkanes in the presence of metallic Ni and ZnAl2O4 phase. Decarbonylation of the octadecanal intermediate and dehydrogenation of 1-octadecanol were key reaction pathways to produce heptadecane, in which decarbonylation was catalyzed by metallic Ni, while the dehydrogenation was attributed to synergistic catalysis between metallic Ni and the strong basic sites of the support. Individual metallic Ni only catalyzed the cleavage of C-H bonds but did not affect the O-H bond of 1-octadecanol.
- Li, Guangci,Chen, Lei,Fan, Ruikun,Liu, Di,Chen, Song,Li, Xuebing,Chung, Keng H.
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p. 213 - 222
(2019/01/14)
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- A green approach of preparation of fine active alumina with high specific surface area from sodium aluminate solution
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Fine active alumina (FAA) with a high specific surface area (SSA) is used in catalysis, adsorbents and other applications. This study presents a novel method of preparing high surface area FAA via a phase evolution from gibbsite through ammonium aluminum
- Wu, Guoyu,Liu, Guihua,Li, Xiaobin,Peng, Zhihong,Zhou, Qiusheng,Qi, Tiangui
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p. 5628 - 5638
(2019/03/02)
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- Enhanced visible emission in Eu3+ doped glass containing Ag-clusters, Ag nanoparticles, and ZnO nanocrystals
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We report the formation of ZnO nanocrystals, Ag-clusters, and Ag nanoparticles in Eu-doped borate glasses by furnace annealing and CO2 laser annealing. The XRD and optical properties of the samples obtained with two techniques were analyzed and
- Bae, Chang-hyuck,Lim, Ki-Soo
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p. 410 - 417
(2019/04/30)
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- Realizing facile regeneration of spent NaBH4 with Mg-Al alloy
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The regeneration of sodium borohydride (NaBH4) is crucial to form a closed cycle after it either supplies hydrogen energy via a hydrolysis process or provides energy through electron transfer at the anode of direct borohydride fuel cells (DBFCs). In both of these cases, the spent fuels are NaB(OH)4 from NaBO2 aqueous solution. However, the current regeneration process from (NaB(OH)4)·xH2O to form NaBH4 by reduction reaction and calcination at high temperature with metal hydrides as reducing agents is very expensive. In this work, we developed a simple regeneration process via ball milling with Mg-Al alloys as the reducing agent for NaB(OH)4 under an argon atmosphere. Under optimized conditions, a high yield of about 72% of NaBH4 could be obtained. Mechanistic study showed that all the hydrogen atoms from NaB(OH)4 remain in NaBH4 and no additional hydrogen sources are needed for the reduction process. The inexpensive Mg-Al alloy works as a reducing agent transforming the H+ to H- in NaBH4. This approach demonstrates a ～20-fold cost reduction compared with the method using metal hydrides. This opens the door to the commercial implementation of simple ball milling processes for the regeneration of spent NaBH4 from NaB(OH)4 with cheap reducing agents.
- Zhong, Hao,Ouyang, Liuzhang,Zeng, Meiqin,Liu, Jiangwen,Wang, Hui,Shao, Huaiyu,Felderhoff, Michael,Zhu, Min
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supporting information
p. 10723 - 10728
(2019/05/06)
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- Plutonium and Americium Aluminate Perovskites
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Both AmAlO3 and PuAlO3 perovskites have been synthesized and characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and 27Al magic angle spinning nuclear ma
- Vigier, Jean-Fran?ois,Popa, Karin,Martel, Laura,Manara, Dario,Dieste Blanco, Oliver,Freis, Daniel,Konings, Rudy J. M.
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p. 9118 - 9126
(2019/07/08)
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- Highly porous α-alumina powders prepared with the self-assembly of an asymmetric PS-: B -PEO diblock copolymer
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Highly porous and abundantly crystallized alumina (Al2O3) powders, can be prepared using an asymmetric polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymer, which critically allowed solid-phase transition from γ- to α-Als
- Kimura, Tatsuo,Maruoka, Hirokazu
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p. 10003 - 10006
(2019/08/22)
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- Mechanochemical Nonhydrolytic Sol-Gel-Strategy for the Production of Mesoporous Multimetallic Oxides
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Mesoporous metal oxides with wide pore size, high surface area, and uniform porous structures have demonstrated excellent advantages in various fields. However, the state-of-art synthesis approaches are dominated by wet chemistry, accompanied by use of ex
- Zhang, Zihao,Yang, Shize,Hu, Xiaobing,Xu, Haidi,Peng, Honggen,Liu, Miaomiao,Thapaliya, Bishnu Prasad,Jie, Kecheng,Zhao, Jiahua,Liu, Jixing,Chen, Hao,Leng, Yan,Lu, Xiuyang,Fu, Jie,Zhang, Pengfei,Dai, Sheng
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p. 5529 - 5536
(2019/08/27)
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- An effective strategy to obtain highly porous alumina powders having robust and designable extra-large pores
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Crystalline alumina is a significant inorganic solid that has been utilized as a high-surface-area catalyst support. However, it has been in fact difficult to obtain alumina having high interior porosity and adequate crystallinity in their powder forms be
- Maruoka, Hirokazu,Kimura, Tatsuo
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p. 1859 - 1866
(2019/11/13)
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- The Study of CrOx-Containing Catalysts Supported on ZrO2, CeO2, and CexZr(1–x)O2 in Isobutane Dehydrogenation
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Olefin hydrocarbons are valuable raw materials for petrochemical and polymer manufacturing. Highly effective, but toxic chromium-containing catalytic materials are the most widely used catalysts to obtain olefins in industry. In this regard, the urgent challenge to increase the efficiency of oil processing is to develop the catalysts with low content of harmful active component. In the present study, the catalysts with low chromium content (1 theoretical monolayer = 5 Cr atoms per nm2 of support) were synthesized by incipient wetness impregnation of the supports (Al2O3, ZrO2, CeO2, and CexZr(1–x)O2). The samples obtained were characterized by low-temperature nitrogen adsorption, X-ray diffraction and H2-temperature-programmed reduction methods. The catalytic properties of the catalysts were tested in isobutane dehydrogenation reaction. It was shown that the state of chromium on the surface is different over different supports. For the CrOx/CeO2 catalyst, the formation of Cr2O3 particles with low activity in the dehydrogenation reaction was observed. For other samples, a highly disperse X-ray amorphous state of chromium was characteristic. The catalyst based on CexZr(1–x)O2 was the most active in isobutane dehydrogenation reaction due to possible stabilization of chromium as Cr(V) state.
- Bugrova,Mamontov
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p. 143 - 149
(2018/04/14)
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- Alumina and silica preparation: Via a sol-gel route with carbon dioxide as a pH regulator-a new method for green catalysis
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This paper presents a new preparation method of SiO2 and Al2O3via a sol-gel route with CO2 as a pH regulator. The influence of carbon dioxide as a pH moderator on the textural parameters is demonstrated. The properties of the oxide xerogels were investigated using SEM, TEM, FT-IR, thermal analysis techniques, and low temperature nitrogen adsorption measurements to describe their structural evolution. The results illustrate differences in the final textural properties of the systems obtained depending on the pH regulator used in the synthesis. The method proposed is doubly beneficial as it eliminates the use of (organic or inorganic) acids and represents an interesting and new application of carbon dioxide.
- Przekop, Robert E.,Sztorch, Bogna,Pietrowski, Mariusz,Zieliński, Micha?,Marty?a, Agnieszka
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p. 7060 - 7065
(2018/05/07)
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- Hybridization of Al2O3 microspheres and acrylic ester resins as a synergistic absorbent for selective oil and organic solvent absorption
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In this study, we have focused on the synthesis, characterization, and oil absorption properties of Al2O3 microspheres/acrylic ester resin (AER) hybrids. The Al2O3 microspheres are prepared by a combined hydrothermal and sintering processes, followed by surface modification with silane coupling agent (KH 570). The Al2O3 microspheres/AER hybrids with a rough surface are synthesized by a microwave polymerization route by using modified Al2O3 microspheres as modifiers. In this hybrid materials system, the Al2O3 microspheres with porous structures may provide fast oil absorption due to the low oils absorption energy and short diffusion lengths. The resin hybrids exhibited reversible oils and organic solvents adsorption with maximum absorption capacities up to 29.85?g/g. This study suggests potential environmental advantage in using metal oxide microspheres in improving the oil absorption properties of oil-absorbing resins as absorbents for recovering oil and organic solvent from water.
- Zhang, Tao,Yue, Xuejie,Yang, Dongya,Guo, Qing,Qiu, Fengxian,Li, Zhangdi
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- Catalytic pyrolysis of Pinus densiflora over mesoporous Al2O3 catalysts
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The thermal and catalytic pyrolysis of Pinus densiflora (P. densiflora) were performed to test the catalytic cracking efficiency of two mesoporous Al2O3 catalysts with different surface areas. Thermogravimetric analysis (TGA) of P. densiflora showed that the differential TG (DTG) peak heights obtained from catalytic pyrolysis were smaller than those of non-catalytic pyrolysis due to the conversion of the reaction intermediates to coke. Pyrolyzer-gas chromatography/mass spectrometry analysis/flame ionization detection (Py-GC/MS/FID) suggested that using the Al2O3 catalysts, the yields of phenols and levoglucosan decreased with a concomitant increase in the yields of aldehydes, alcohol, ketones, and furans. Between the two catalysts, Al2O3-B prepared by spray pyrolysis showed higher cracking efficiency than Al2O3-A prepared by hydrothermal method because of its larger surface area.
- Kim, Young-Min,Rhee, Gwang Hoon,Ko, Chang Hyun,Kim, Ki Hoon,Jung, Kyeong Youl,Kim, Ji Man,Park, Young-Kwon
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p. 6300 - 6303
(2018/04/30)
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