Search

Abstract: The stereoselective hydrogenation of phenyl acetylene and 1-phenyl-1-hexyne at 298K and atmospheric pressure of H2 over Pd catalysts supported on mesostructured silica was studied. The catalysts were prepared by the impregnation of HMS and MSU-X silicas with 3-D wormhole framework structures and MCM-41 silica with a 1-D hexagonal framework using a toluene solution of Pd(acac)2 to obtain a metal content close to 1wt.%. All the supports were characterised by nitrogen adsorption–desorption isotherms at 77K and XRD. The catalysts were characterized by H2 chemisorption and TEM measurements. The reactions were found to be zero order with respect to the phenyl acetylene and 1-phenyl-1-hexyne concentration. Each catalyst presented a different catalytic performance. The 1%Pd/HMS catalyst was the most active in comparison with the 1%Pd/MSU-X and 1%Pd/MCM-41 catalysts. This superior performance in the case of the HMS support was attributed to the presence of interconnected framework channels and textural mesoporosity that can increase the accessibility of the Pd centers to a greater extent than the more monolithic MSU-X and MCM-41 supports. All catalysts displayed high selectivity to styrene and cis-1-phenyl-1-hexene compounds. [Copyright &y& Elsevier]

Abstract: Advanced heterogeneous catalysts for olefin metathesis were prepared by supporting Re(VII) oxide on (i) mesostructured γ-aluminas with lath-like and scaffold-like morphologies and (ii) organized mesoporous alumina with wormhole-like pore structure. The thermal spreading method was found to be very suitable technique for preparation of a highly active catalyst. In the case of dec-1-ene metathesis, Re(VII) oxide catalysts supported on mesoporous aluminas exhibited a high activity and selectivity independently of the type of catalyst support. For metathesis of olefin functional derivatives, namely p-allylanisole and diethyl diallylmalonate, the activity of Re(VII) catalysts with optimum amount of Re(VII) being 9.0wt% (with Me4Sn as co-catalyst) was found to depend on the catalyst pore size. Catalyst prepared from mesoporous aluminas with pore sizes at least 4.0nm exhibited much higher conversions of substrates compared with catalysts of 3.5nm pores. [Copyright &y& Elsevier]

Abstract: The in situ upgrading of biomass pyrolysis vapors with two mesoporous aluminosilicate materials (MSU-SBEA) assembled from zeolite Beta (BEA) seeds was tested in the present study, in comparison to conventional Al-MCM-41 and to non-catalytic biomass pyrolysis. The first sample (MSU-S/HBEA) exhibited an hexagonal mesopore structure while the second one (MSU-S/WBEA) possessed a wormhole-like mesopore structure with high textural porosity. The catalytic tests were performed on a fixed-bed reactor, the reaction temperature was 500°C and the feed was a lignocellulosic biomass based on beech wood. The use of the MSU-S catalytic materials led to significantly lower organic phase in the produced bio-oil and also to higher coke and char yields, compared to non-catalytic pyrolysis and to the use of Al-MCM-41 which induced a small increase in the yields of liquid oil and coke. Pyrolysis gases were also affected by all mesoporous catalysts. The MSU-S catalytic materials were very selective towards polycyclic aromatic hydrocarbons (PAHs) and heavy fractions, while they produced negligible amounts of acids, alcohols and carbonyls, and very few phenols. The MSU-S materials appeared to possess stronger acid sites than Al-MCM-41, resulting in enhanced yields of aromatics, PAHs and coke, as well as propylene in the pyrolysis gases. [Copyright &y& Elsevier]

A mesostructured γ-alumina with a lathlike framework morphology, denoted MSU-γ, has been prepared according to previously described methods through the reassembly and crystallization of a mesostructured alumina precursor with initially amorphous framework walls and used as a support for the catalytic hydrodesulfurization (HDS) of dibenzothiophene (DBT). The alumina support was loaded with molybdenum and cobalt ions via incipient wetness impregnation methods and then converted to the active sulfide form by reaction with H2S. HDS reactions of DBT were carried out at 400 °C and 400 psi to achieve a DBT conversion of 69–77% and a biphenyl (BP) product selectivity of 60–64% after a reaction time of 3 h, indicating that most of the DBT could undergo desulfurization while limiting excessive hydrogen consumption through aromatic hydrogenation. Although the dispersion of the active Mo/Co sulfide phase supported on lathlike MSU-γ alumina remained very high after several hours on stream, the conversions most likely were limited by a loss of surface area and porosity under HDS conditions. [Copyright &y& Elsevier]