Heterogeneously catalyzed reactive extraction for biomass valorization into chemicals and fuels

This paper focuses on the heterogeneously catalyzed reactive extraction and separation in reaction steps in organic and aqueous phases during the transformation of biomass derived products. Two approaches are demonstrated for decomposing and preserving routes for biomass transformation into valuable products. The decomposing approach has been validated by transformation of glycerol into building blocks like CO, CO2 and H2 by aqueous phase reforming (APR) in the aqueous phase with simultaneous synthesis of hydrocarbons by Fischer-Tropsch synthesis (FTS) in the organic phase. The preserving approach has been validated by the dehydration of xylose over acidic catalyst with the hydrogenation of formed furfural in the organic phase. As a result, selectivities in the range of 30–50% to the wax and tetrahydrofurfuryl alcohol, respectively, have been obtained by application of reactive extraction for both approaches

Transient Studies of the Elementary Steps of FischerTropsch Synthesis

International audienceThe pulse transient method has been used to study the kinetics of several key steps of Fischer-Tropsch (FT) synthesis over cobalt supported catalysts. These elementary steps involve chemisorption of hydrogen and propene, and chemisorption and hydrogenation of carbon monoxide. It is found that at the conditions of Fischer-Tropsch synthesis, hydrogen chemisorption is reversible and quasi-equilibrated, while carbon monoxide adsorption is generally irreversible. Chemisorption of propene on cobalt metal sites results in its rapid autohydrogenation to propane and simultaneous formation of C xHy surface species. The transient response curves produced during hydrogenation of carbon monoxide pulses in a flow of hydrogen have been analyzed using the modified Kobayashi model, which involves irreversible chemisorption and dissociation of carbon monoxide, quasi-equilibrated adsorption of hydrogen and reversible adsorption of water. The kinetic analysis suggests that oxygen-containing species are probably the most abundant surface intermediates. Desorption of water from the catalysts seems to be much slower than hydrogenation of surface carbon species. © 2005 Elsevier B.V. All rights reserved

Ion-exchanged zeolite P as a nanostructured catalyst for biodiesel production

International audienceNano-crystalline synthetic gismondine modified via cation exchange has been utilised as a highly active and selective catalyst for the production of biofuel. In comparison with low silica zeolites FAU and LTA, K-form of gismondine, based on the maximum aluminium P (MAP) zeolite, exhibited a significant improvement in catalytic performance in the methanolysis of bio-oil, which can be attributed to its nano-particle morphology and high basicity associated with the high Al content and high degree of ion exchange, as demonstrated by the TEM, XRD, TGA, NMR, XPS and CO 2 -TPD studies. To the best of our knowledge, this is the first report on a successful catalytic application of basic K-MAP zeolite. © 2019 The Author

Effects of ?-cyclodextrin introduction to zirconia supported-cobalt oxide catalysts: From molecule-ion associations to complete oxidation of formaldehyde

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Cobalt dispersion, reducibility, and surface sites in promoted silica-supported Fischer–Tropsch catalysts.

International audienceCobalt particle size, cobalt reducibility, and metal surface sites in a series of ruthenium- and rhenium-promoted cobalt silica-supported Fischer– Tropsch catalysts were studied by X-ray diffraction, UV–vis spectroscopy, in situ X-ray absorption, in situ magnetic method, X-ray photoelectron spectroscopy, DSC-TGA thermal analysis, and propene chemisorption. The catalysts were prepared by co-impregnation; in several catalyst syntheses, sucrose was added to the impregnating solutions. Mononuclear octahedral cobalt complexes were observed in the catalysts after impregnation and drying. Cobalt repartition on silica in the impregnated and dried catalysts depended primarily on the pH of the impregnating solution. Cobalt repartition was uniform on the silica surface if the pH of the impregnating solution was higher than the point of zero charge (PZC) of silica, but was less uniform at pH below that of the PZC of silica. Cobalt dispersion proceeded during catalyst calcination in air. Decomposition of cobalt nitrate and crystallization of cobalt oxide seemed to be the crucial steps in the preparation of highly dispersed cobalt catalysts. Promotion with noble metals resulted in greater cobalt dispersion, probably due to higher concentrations of cobalt oxide crystallization sites. Addition of sucrose modified the structure of supported cobalt complexes and led to higher temperatures of crystallization of cobalt oxide and to catalysts with extremely high cobalt dispersion. In situ magnetization measurements show that promotion with Ru moderated the temperature of reduction of cobalt oxide to metal phases, whereas the effect was less significant for Re-promoted catalysts. The addition of sucrose during impregnation, although significantly enhancing cobalt dispersion, did not diminish cobalt reducibility. Due to a combination of high cobalt dispersion and reducibility, the ruthenium- and rhenium-promoted catalysts prepared using sucrose had the highest number of cobalt metal surface sites. Fischer–Tropsch reaction rates were determined principally by the number of cobalt surface sites, with high cobalt dispersion and easy reducibility resulting in more active Fischer–Tropsch catalysts

The role of external acid sites of ZSM-5 in deactivation of hybrid CuZnAl/ZSM-5 catalyst for direct dimethyl ether synthesis from syngas

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MODELISATION OF A FIXED BED REACTOR FOR FISCHER TROPSCH SYNTHESIS WITH DEACTIVATION

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