Study of the origin of the deactivation of a Pt/CeO2 catalyst during reverse water gas shift (RWGS) reaction

The effect of carbon deposition in the deactivation of a 2% Pt/CeO2 under RWGS conditions was investigated via an accelerated ageing procedure consisting of measuring the catalyst activity (under 1% CO2, 4% H-2, 300 degreesC) before and after exposure to CO, CO2, H-2, or CH4 at 400 C. Exposure to CO led to severe deactivation while exposure to CO2, CH4, or H-2 led to moderate or no deactivation. Additional activity measurements performed before and after exposure to CO followed by subsequent temperature-programmed oxidation (TPO) showed that exposure to increasing amounts of CO led to increased deposits of carbon and deactivation. No evidence for metal sintering was found. Additional TPO following catalyst exposure to RWGS conditions evidenced the deposition of carbonaceous deposits under the RWGS reactant mix. (C) 2004 Elsevier Inc. All rights reserved.