CrO /SiO2 mesoporous catalysts prepared using beta-cyclodextrin as a template and their catalytic properties in propane oxidative dehydrogenation in the presence of carbon dioxide

Abstract

This work is aimed at the preparation and investigation of CrOx/SiO2 catalysts of oxidative propane dehydrogenation in the presence of carbon dioxide. The mesoporous silicas used as carriers were prepared via a sol-gel method using a beta-cyclodextrin and urea mixture as a template. The amounts of water added during Si(OEt)4 hydrolysis and chromium oxide loading were varied. The obtained catalysts were characterised via nitrogen low-temperature adsorption-desorption, XRD, SAXS, SEM with EDX, TEM, XPS, UV–Vis diffuse reflectance spectroscopy and the catalytic tests. The obtained mesoporous silicas have monomodal narrow pore size distributions with the maxima at 7, 9, 10 nm increasing when the amounts of water used during the synthesis increase, and large surface areas of 680, 460, 410 m2g-1, respectively. All the samples do not contain micropores. Chromium oxidation states +6 and + 3 were found according to XPS and UV–Vis diffuse reflectance spectroscopy data. The catalytic tests revealed that there is a correlation between the catalytic activity and synthesis conditions. The catalytic activity in the reaction of oxidative propane dehydrogenation in the presence of CO2 decreases in the series with a pore diameter of 9 > 10 > 7 nm. The most active and selective sample showed the selectivity to propylene up to 80% while the conversion was 20%.