Abstract
Solid acid catalysts based on WO3–SiO2 and WO3–ZrO2–SiO2 were prepared by one-pot non-hydrolytic sol–gel method and tested in the gas phase glycerol dehydration to acrolein. Their structural and textural characteristics were determined by X-ray diffraction (XRD), N2 adsorption, X-ray energy dispersive spectroscopy (XEDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Their acid characteristics were studied by both temperature programmed desorption of ammonia (NH3-TPD) and FTIR of adsorbed pyridine. Under our operating conditions, all the catalysts were active and selective in the transformation of glycerol to acrolein, which was always the main reaction product. The high selectivity to acrolein is achieved on catalysts presenting a higher proportion of Brønsted acid sites. In addition, the role of oxygen in the feed on catalytic performance of these catalysts is also discussed.
Highlights
The utilization of biomass as renewable feedstock for the substitution of fossil sources constitutes a promising alternative in moving our economy toward a more sustainable future.[1,2,3] Nowadays, about 85% of world commercial energy is obtained from fossil fuels and biodiesel.[2]
We describe the one-step Non-hydrolytic sol–gel (NHSG) preparation of WO3–SiO2 and WO3–ZrO2–SiO2 materials, in which the W-content is varied in a systematic way
WO3–SiO2 and WO3–ZrO2–SiO2 catalysts have been prepared by the non-hydrolytic sol–gel method, under argon atmosphere inside a glove box according to a method previously reported,[22,23,24,25,26] using SiCl4 (Sigma Aldrich, 99.9%), ZrCl4 (Sigma Aldrich, 99.9%), WCl6 (Sigma Aldrich, 99.5%), anhydrous dichloromethane (CH2Cl2, Aldrich, 99.8%) and diisopropyl ether as reactants
Summary
The utilization of biomass as renewable feedstock for the substitution of fossil sources constitutes a promising alternative in moving our economy toward a more sustainable future.[1,2,3] Nowadays, about 85% of world commercial energy is obtained from fossil fuels and biodiesel.[2]. Shown to provide an excellent control over the stoichiometry and homogeneity of mixed oxide gels.[22,23,24,25,26] This ether route is based on the in situ formation of alkoxide groups by reaction of the halide groups with the ether, followed by non-hydrolytic condensation between these alkoxide groups and the remaining chloride groups.[26] Owing to the generally high degree of condensation of non-hydrolytic gels, mesoporous xerogels with high surface area and pore volume can be obtained by simple evaporative drying in the absence of templating agent These non-hydrolytic routes are attracting increasing attention for the preparation of W-containing mixed oxide catalysts.[22,23,24,25]. These catalysts were characterized by N2-physisorption, XRD, NH3-TPD, FTIR of adsorbed pyridine, XEDS, and FTIR, Raman and XPS spectroscopies and tested in the dehydration of glycerol to acrolein
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