Combustion of methane over palladium catalyst in the presence of inorganic compounds: inhibition and deactivation phenomena

The influence of the presence of different inorganic gases, often found in methane-containing industrial off-gases (NH3, NO2, H2, H2O, SO2, H2S, CO and CO2) on the catalytic combustion of methane over a Pd/Al2O3 catalyst is studied in the present work, in a range of concentrations corresponding to typical industrial emissions, such as those of coke oven facilities. Results show that the effect of SO2 and H2S on the catalyst is similar, both compounds causing partially irreversible poisoning, whereas water (present in the feed or formed by combustion of H2 or CH4) causes reversible inhibition in the absence of sulphur compounds. Nitrogen-containing compounds increase methane conversion in the absence of sulphur-containing compounds, but ammonia has the opposite effect when sulphur compounds are present. The other compounds studied do not affect appreciably the catalytic combustion of methane.