Study of catalyst deactivation and reaction mechanism of steam reforming, partial oxidation, and oxidative steam reforming of ethanol over Co/CeO2 catalyst

A reaction mechanism was proposed based on in situ DRIFTS and ethanol TPD. Reaction type, feed ratio, and temperature influence amounts and types of carbon deposited and in turn, catalyst stability. The mechanisms of Co/ceria catalyst deactivation during steam reforming, oxidative steam reforming, and partial oxidation of ethanol were explored by comparing the results from different characterization techniques with those obtained from catalytic testing in a fixed-bed reactor. The nature of carbon deposition and the reaction conditions played critical roles in determining the extent of a catalyst deactivation. To shed light on the modes of carbon deposition under different reaction conditions, the mechanisms by which the adsorbed surface species turned over on the catalyst surface were evaluated using diffuse reflectance infrared spectroscopy under reaction conditions and temperature-programed desorption of adsorbed ethanol. In steam reforming, ethoxy species were converted to acetate and steam promoted forward acetate demethanation. The resulting methane decomposed on Co metal particles. In this case, carbon diffused through the Co particle, nucleating growth sites for filamentous carbon behind it, with the resulting filaments lifting Co from the support. High H2 O/ethanol ratios and oxygen promoted cleaning of the cobalt surface.[PUBLICATION ABSTRACT]