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Applied Catalysis A, General (v.300, #1)
Highly dispersed iron oxide nanoclusters supported on ordered mesoporous SBA-15: A very active catalyst for Friedel–Crafts alkylations by Yinyong Sun; Stéphane Walspurger; Jean-Philippe Tessonnier; Benoît Louis; Jean Sommer (pp. 1-7).
Iron oxide supported on ordered mesoporous SBA-15 was prepared by impregnating as-synthesized SBA-15 with a methanolic solution of Fe(NO3)3·9H2O, characterized by X-ray diffraction (XRD), N2 sorption, transmission electron microscopy (TEM), and UV–vis spectroscopy. Characterization revealed that iron oxide was present as highly dispersed nanoclusters in the well-ordered mesoporous channels of SBA-15. The supported material still maintained its ordered mesoporous structure similar to SBA-15 and possessed high surface area, large pore volume and uniform pore size.The benzylation of benzene by benzyl chloride showed that iron oxide nanoclusters-supported SBA-15 was a very active catalyst and able to activate the reactant at relatively low temperature such as 313K. Moreover, the catalyst could be reused. Such outstanding catalytic performance should be attributed to the presence of active sites from iron oxide nanoclusters, large surface area, open pore channels, and high pore volume. Additionally, the catalyst has found potential applications in other Friedel–Crafts alkylations, especially to large molecular reactions due to its ordered mesoporous structure.
Keywords: Iron oxide; Nanoclusters; SBA-15; Ordered mesoporous; Friedel–Crafts; Alkylation; Benzyl chloride; Benzylation
Hydrogen production via the catalytic cracking of ethane over Ni/SiO2 catalysts by Soo Yin Chin; Ya-Huei Chin; Michael D. Amiridis (pp. 8-13).
The catalytic decomposition (“cracking�) of ethane was studied over a Ni/SiO2 catalyst at temperatures ranging between 450 and 650°C. In addition to hydrogen and filamentous carbon, methane is also formed during this process as a by-product. SEM images of the spent catalyst indicate the formation of carbon filaments of approximately 50nm in diameter, almost identical to the original Ni particle size in the fresh catalyst. Measurements conducted at different temperatures and space velocities suggest that hydrogen is the primary product, while methane is formed in a secondary step, presumably the hydrogenation of surface carbon or CH y fragments. Almost complete initial conversion of ethane is observed at a space velocity of 18000mL/gh at temperatures above 500°C. Although the initial yield of hydrogen increases with temperature, the rate of catalyst deactivation also increases at higher temperatures. As a result, the overall amounts of hydrogen produced and ethane converted over the lifetime of the catalyst reach maxima at 500°C.
Keywords: Ethane cracking; Hydrogen production; Ni/SiO; 2; Carbon filaments
Catalytic and physical characteristics of axially modified cobalt (III) tetraphenyl porphyrin immobilized on chemically different supports by Salah A. Hassan; Hamdi A. Hassan; Khaled M. Hashem; Hany M. Abdel Dayem (pp. 14-23).
A newly synthesized binuclear cobalt (III) axial-methyl alcohol-hydrochloric acid-tetraphenyl porphyrin complex was supported on the surface of two carriers of different anchoring sites, silica gel as an inorganic carrier and DOWEX-50 HGR ion-exchange resin as an organic one. Complex loading ranged between 0.1 and 2.0% (w/w). The studied complex was shown to exhibit weaker interaction with silica gel surface, where it existed as mononuclear molecules in the diluted samples and as aggregated binuclear ones in the more concentrated samples. In the diluted samples on the resin, the complex molecules seemed to be inserted in the voids, freely and favorably oriented toward the ion exchange groups. With more concentration, part of the complex molecules was assumed to escape through diffusion from internal voids to the outer surface. The major part seemed to display associative ion exchange, where dissociation or break up of hydrogen-bonded sulphonate groups was the controlling step. The catalase-like activity of the various complex samples under study was shown to run in linear relationship with the dispersion parameter being a function of the mode of complex interaction with the support. The active site for the unsupported complex was suggested to involve both the π-electron cyclic system and the central cobalt ion. For supported complex samples, operating active sites seemed to be only the central cobalt ions, where the axial ligands, with the macro-ring system, might play the role of controlling the orientation, dispersion and distribution of complex molecules on the support surface.
Keywords: Axially modified CoTPP; Immobilized; Apparent dispersion; Catalase-like activity
Photoelectrocatalytic destruction of organics using TiO2 as photoanode with simultaneous production of H2O2 at the cathode by W.H. Leng; W.C. Zhu; J. Ni; Z. Zhang; J.Q. Zhang; C.N. Cao (pp. 24-35).
Research on the photoelectrocatalytic (PEC) oxidation of organic contaminants, the role of cathodes during photocatalysis has usually been disregarded. This paper reports a study of the PEC decomposition of aniline and salicylic acid with simultaneous production of hydrogen peroxide in a divided reactor using TiO2 as a photoanode. Two types of TiO2 electrode were used. Thermal oxidation electrodes (TO–TiO2) were made by oxidation of titanium metal sheet; sol–gel electrodes (SG–TiO2) were made by coating and then heating a layer of titania gel on titanium sheet. Saturated photocurrent was used to carry out an initial characterization and optimization of both electrode types. The best TO–TiO2 electrodes were prepared by heating titanium at 600–700°C in air. For the SG–TiO2 electrodes, optimum performance was obtained by heating at 500°C. These electrodes were then used to photodegrade aniline and salicylate. The SG–TiO2 electrodes turned out to be superior to the TO–TiO2 electrodes in terms of PEC rate under the same conditions but the difference in rate between the two electrodes was comparable under a high enough bias potential. The most important factors affecting the production of H2O2 in the cathode compartment are presented. The current efficiencies for the accumulation of H2O2 were remarkably affected by the cathode used, pH value, current density, and metal cations such as copper and iron ions. An expected H2O2 concentration could be obtained by controlling either the magnitude of the photocurrent or illumination time. The maximum current efficiency for the cathodic reduction of oxygen to H2O2 was as high as 90.1% when graphite was used as the cathode. Compared to the SG–TiO2 electrode, the TO–TiO2 electrode had a higher light to electricity conversion efficiency, thus it turned out to be more suitable for the production of H2O2. Furthermore, the role of in-situ reduced oxygen species in the PEC decomposition of aniline was evaluated.
Keywords: Photoelectrocatalytic; Thermal oxidation electrodes; Sol–gel electrodes; Titanium dioxide (TiO; 2; ); Hydrogen peroxide production
Dehydration of alcohols in the presence of carbonyl compounds and carboxylic acids in a Fischer–Tropsch hydrocarbons matrix by F.H.A. Bolder; H. Mulder (pp. 36-40).
The dehydration of alcohols in the presence of carboxylic acids, ketones and aldehydes in Fischer–Tropsch hydrocarbon fractions was investigated over η-alumina at different temperatures and mass hourly space velocities. Quantitative dehydration of the alcohols was achieved while reactions of carbonyl compounds and acids were incomplete and short-lived. At least 70% of the α-olefins in the feed were initially isomerised to internal olefins, while primary alcohols were dehydrated to mostly internal olefins. Over a period of 8 days, at 350°C and a liquid hourly space velocity of 6L feed/(Lcath−1), isomerisation of olefins gradually ceased until the fraction of α-olefins equalled the original concentration in the feed (16mass%) plus the fraction formed from the dehydration of alcohols (8mass%). The conversion of carbonyl compounds and acids also diminished to a negligible level. The isomerisation activity was linked to catalyst sites which were selectively poisoned by carbonyl compounds and acids. Regeneration of the catalyst with oxygen at a temperature of 480°C resulted again in removal of carbonyl compounds and acids as well as olefin isomerisation. The alcohol dehydration reaction appeared not to be affected by the poisoning of the catalyst.
Keywords: Alcohol; Dehydration; Carbonyl compound; Ketone; Aldehyde; Carboxylic acid; Olefin isomerisation; Alumina; Catalyst regeneration
Influence of the addition of H2 upon the behavior and properties of a Pd(2wt.%)/γ-Al2O3 catalyst and a comparison with the case of the Pt-based catalyst by O. Demoulin; I. Seunier; M. Navez; P. Ruiz (pp. 41-49).
The influence of adding H2 in the feed during catalytic combustion of methane (CCM) on a Pd(2wt.%)/γ-Al2O3 catalyst is studied. Various effects on the performances of the catalyst are observed, depending on the H2 concentration. Activation is observed at low H2 concentrations, but if too large concentrations of hydrogen are used (5vol.% in this case), reduction of the surface of the palladium particles occurs and deactivation of the catalyst is therefore observed. A mechanistic interpretation is proposed, which explains the experimental observations. A comparison is also made with the characteristics of a Pt(2wt.%)/γ-Al2O3 catalyst. Both catalysts display different behavior towards the presence of H2, which probably reflects different reaction pathways for CCM.
Keywords: Catalytic combustion; Methane oxidation; Hydrogen; Palladium; Platinum
Dehydration of butanediols over CeO2 catalysts with different particle sizes by Ai Igarashi; Naoki Ichikawa; Satoshi Sato; Ryoji Takahashi; Toshiaki Sodesawa (pp. 50-57).
Dehydration of butanediols into unsaturated alcohols was investigated over CeO2 with different particle sizes. The size was controlled by the calcination temperature. Catalytic performance in the dehydration of 1,3-butanediol is greatly affected by the particle size. The selectivity to unsaturated alcohols such as 3-buten-2-ol and trans-2-buten-1-ol increases with increasing the particle size, while decomposition of 1,3-butanediol into methanol and ethanol is catalyzed by CeO2 with small particles. In contrast, in the reaction of 1,4-butanediol, cyclization products such as tetrahydrofuran and γ-butyrolactone increases with decreasing the particle size, instead of the decomposition into methanol and ethanol. CeO2{111} facets became predominant on the large particles, whereas different surfaces such as {100} and {110} facets were exposed on the small CeO2 particles. In the dehydration of butanediols, CeO2 has structure-sensitive catalysis: CeO2{111} facets have active sites for the formation of unsaturated alcohols, and the other surfaces catalyze the side reactions such as decomposition of 1,3-butanediol and cyclization of 1,4-butanediol.
Keywords: Dehydration; Butanediol; Unsaturated alcohol; Ceria
Effect of support on the activity of Ga2O3 species for steam reforming of dimethyl ether by Thomas Mathew; Yusuke Yamada; Atsushi Ueda; Hiroshi Shioyama; Tetsuhiko Kobayashi; Chinnakonda S. Gopinath (pp. 58-66).
The effects of various supports on the catalytic activity of Ga2O3 for the steam reforming of DME have been examined. Among the various supported Ga2O3 catalysts, Ga2O3/TiO2 showed the highest DME steam reforming activity in terms of DME conversion and H2 yield. The results from XRD, surface area and XPS indicate that the dispersion of Ga2O3 strongly depends on the catalyst support. A correlation between the XPS results and the DME steam reforming activity reveals that there is some electronic interaction between Ga2O3 and the support element. The large electronic interaction found in Ga2O3/TiO2 leads to the best catalytic performance among all the catalysts.
Keywords: Fuel cells; DME steam reforming; Supported Ga; 2; O; 3; Mixed oxides; XPS; Hydrogen
Transesterification of soybean oil catalyzed by potassium loaded on alumina as a solid-base catalyst by Wenlei Xie; Hong Peng; Ligong Chen (pp. 67-74).
Biodiesel fuel, consisting of methyl esters of long chain fatty acids produced by transesterification of vegetable oils or animal fats with methanol, is a promising alternative diesel fuel regarding the limited resources of fossil fuels and the environmental concerns. In this work, an environmentally benign process for the transesterification of soybean oil to methyl esters using alumina loaded with potassium as a solid base catalyst in a heterogeneous manner was developed. The catalyst loaded KNO3 of 35wt.% on Al2O3, after being calcined at 773K for 5h, it was found to be the optimum catalyst, which can give the highest basicity and the best catalytic activity for this reaction. The effects of various reaction variables such as the catalyst loading, oil to methanol ratio, reaction time and temperature on the conversion of soybean oil were investigated. The catalysts were characterized by means of XRD, IR and Hammett titration method. The results indicated that K2O derived from KNO3 at high temperature and that the Al–O–K groups were, probably, the main reasons for the catalytic activity towards the reaction. The catalyst activity was correlated closely with its basicity as determined by the Hammett method.
Keywords: Heterogeneous catalyst; Transesterification; Biodiesel; Loading of KNO; 3; on Al; 2; O; 3; Calcination
Development of oxygen transport membrane La0.2Sr0.8CoO3− δ/Ce0.8Gd0.2O2− δ on the tubular CeO2 support by Xiong Yin; Liang Hong; Zhao-Lin Liu (pp. 75-84).
The oxygen-permeable ceramic membrane (OPCM), made of the mixed-conductive ceramic oxide Gd0.2Ce0.8O2− δ (GCO20), has been successfully fabricated on a porous CeO2 tubular support by means of the slurry-coating and co-sintering techniques. In this asymmetric membrane, the GCO20 membrane (10–20μm thick) is intercalated in the surface layers of a porous CeO2 tube. It gives an O2 permeation flux of 0.45sccm/cm2 from air feed at 900°C and 1bar with exclusive permselectivity. To promote oxygen flux at relatively lower separation temperatures, a thin layer of La0.2Sr0.8CoO3− δ (LSCO80) was deposited on top of GCO20/CeO2 to generate a dual-layer membrane. Nevertheless, raising the calcination temperature to consolidate the outer LSCO80 layer will suppress the oxygen flux. Based on SEM and XRD investigations, this phenomenon is due to removal of fractal surface features and distortion of LSCO80 crystalline phase. Furthermore, the temperature leverages on oxygen ionic conduction were assessed using impedance analysis. The electric measurement results are in agreement with the oxygen permeation testing results. Finally, the density function theory (DFT) was applied to perform simulations in order to find out the dependence of the equilibrium dimension of lattice cell on the oxygen vacancy concentration in the perovskite LSCO80 structure at the ground state of the crystal. The outcome shows that the lattice undergoes expansion upon losing oxygen, which provides a theoretical explanation for the crystalline distortion induced by high calcination temperature.
Keywords: Oxygen-permeable ceramic electrolyte; Gd doped ceria; Asymmetric membrane; Impedance analysis
KAl(SO4)2·12H2O supported on silica gel as a novel heterogeneous system catalyzed biginelli reaction by Javad Azizian; Ali A. Mohammadi; Ali R. Karimi; Mohammad R. Mohammadizadeh (pp. 85-88).
3,4-Dihydropyrimidin-2(1 H)-ones derivatives were synthesized in moderate to high yields in one-pot three component reaction from the corresponding aldehydes, ketones or 1,3-dicarbonyl compounds and urea, in the presence of catalytic amount of KAl(SO4)2·12H2O (Alum) supported on silica gel (Alum-SiO2) as a non-toxic, reusable, inexpensive and easily available reagent, under solvent-free conditions at 80°C. Compared to the classical Biginelli reaction, this new method consistently has the advantage of good yields.
Keywords: KAl(SO; 4; ); 2; ·12H; 2; O-SiO; 2; (Alum-SiO; 2; ); Biginelli reaction; Solvent-free conditions; Di-hydropyrimidinones; 1,3-Dicarbonyl; Aldehydes; Ketone; Urea