Effect of SO2 on the catalytic activity of SnO2 and CeO2 in methane oxidation

The variation of the catalytic activity of tin and cerium dioxides in the combustion of SO2-containing methane has been investigated at SO2 concentrations of 50 to 1000 ppm in the gas stream. The catalytic activity of SnO2 decreases dramatically upon the introduction of SO2, but it returns rapidly to its initial level and then remains invariable (95% conversion, operating temperature of 600A degrees C). Cerium dioxide is much less resistant to poisoning with sulfur dioxide: the higher the SO2 concentration in the gas stream, the larger the decrease in its activity. After sulfur dioxide is cut off, CeO2 regains its initial activity at 750A degrees C. The behaviors of SnO2 and CeO2 are in agreement with the thermal stabilities of the corresponding sulfates and oxosulfates.