Oxidative dehydrogenation of ethane with CO2 over CrOx catalysts supported on Al2O3, ZrO2, CeO2 and CexZr1-xO2

摘要

The effect of the support nature on the catalytic activity and stability of CrOx-containing catalysts supported on gamma-Al2O3, ZrO2, CeO2 and CexZr(1-x)O2 has been investigated in the oxidative dehydrogenation of ethane with CO2 as a mild oxidant (ODH-CO2). The catalysts were prepared by wetness impregnation and characterized as-prepared and after catalytic tests using N-2 adsorption, XRD, UV-Vis diffuse reflectance (DR) and Raman spectroscopies, TPR-H-2 and TPO-CO2. The catalysts CrOx/gamma-Al2O3 and CrOx/ZrO2 exhibited the highest ethylene formation rates, but the reaction followed different pathways on each: on CrOx/gamma-Al2O3 catalyst ethylene is formed by a direct dehydrogenation (DDH) of ethane accompanied by RWGS, while on CrOx/ZrO2 ethylene is formed by selective oxidative dehydrogenation. The nature of the support influences the oxidation state of chromium species. The reaction pathway, catalytic activity and stability of the catalyst depend on both chromium state and support properties, in particular, on its acid-base and red-ox properties.