The durability of alumina supported Pd catalysts for the combustion of methane in the presence of SO2

In the present work, the 1.0 wt% Pd/gamma-Al2O3, 1.0 wt% Pd/10 wt% CeO2/gamma-Al2O3 and 1.0 wt% Pd/10 wt% Ce0.6Zr0.4O2/gamma-Al2O3 catalysts were prepared and used for the catalytic combustion of methane. The durabilities of the three catalysts were investigated based on the phenomena of SO2 poisoning in methane catalytic combustion. The presence of SO2 in the reaction gases resulted in an increase of 70-250 degrees C in light-off temperature for methane conversion over all the catalysts. The sulfates could be formed below and decomposed above 600-700 degrees C in the reaction over the catalysts, which led to the inhibition and recovery of the catalytic activity, respectively. The introduction of CeO2 or Ce0.6Zr0.4O2 decreased the decomposition temperature of sulfates by 50-100 degrees C. Sulfur accumulation on the catalyst surface was investigated by sulfur content analysis and TG measurements after pretreatment with SO2. The saturated sulfur contents were all about 5 wt% for the three catalysts. In spite of sulfur poisoning, no obvious changes in the particle morphologies and sizes were observed for the fresh and used catalysts. (C) 2011 Elsevier B.V. All rights reserved.