Deactivation and regeneration of Rh/CeO₂-ZrO₂ catalyst for low-temperature steam reforming of ethanol

Ethanol steam reforming (ESR) deactivation experiments on Rh/CeO₂-ZrO₂ have been conducted in order to study the effect of the ceria-zirconia ratio, the cause of deactivation and the regeneration behavior for this catalyst. Tests performed at high space velocity and 450 °C on a series of catalysts with varying ceria-zirconia ratios have shown best hydrogen selectivity and performance stability for 2% Rh/Ce_0.8Zr_0.2O₂. The cause of deactivation and regenerability was investigated in this catalyst by exposing the spent catalyst to low concentrations of oxygen. Evidence indicates that carbonaceous intermediates accumulate on the catalyst as it deactivates at 350 °C and high space velocity, reaching a maximum amount of about 0.9 mmol/g as the residual ESR conversion stabilizes at about 6%. About one third of the carbonaceous material is removed at room temperature in the presence of oxygen, while the remaining deposits could be oxidized at 200-210 °C with full recovery of catalyst activity.