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/γ-Al2O3, 1.0 wt% Pd/10 wt% CeO2/γ-Al2O3 and 1.0 wt% Pd/10 wt% Ce0.6Zr0.4O2/γ-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 °C in light-off temperature for methane conversion over all the catalysts. The sulfates could be formed below and decomposed above 600–700 °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 °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.
Graphical abstractPd/γ-Al2O3, Pd/CeO2/γ-Al2O3 and Pd/Ce0.6Zr0.4O2/γ-Al2O3 are prepared by impregnation method. Catalyst durability is investigated for methane combustion in the presence of SO2. It is found that catalyst poisoning is due to sulfate formation, CeO2 or Ce0.6Zr0.4O2 introduction lowers sulfate decomposition temperature by 50–100 °C, and the saturated sulfur content is about 5 wt% for each catalyst.Figure optionsDownload full-size imageDownload high-quality image (267 K)Download as PowerPoint slideHighlights► Pd/Al2O3, Pd/CeO2/Al2O3 and Pd/Ce0.6Zr0.4O2/Al2O3 are prepared by impregnation method. ► The durability of the catalysts is studied for methane combustion in the presence of SO2. ► The poisoning of the catalysts is due to the formation of sulfates on the catalyst surfaces. ► CeO2 or Ce0.6Zr0.4O2 introduction lowers sulfate decomposition temperature by 50–100 °C. ► The saturated sulfur content of each of the three catalysts is about 5 wt%.
Journal: Catalysis Today - Volume 175, Issue 1, 25 October 2011, Pages 223–230