Role of the Catalyst Support in the Oxidation of Methane over Palladium

Abstract

The influence of the catalyst support on the oxidation of methane over palladium has been studied using a microcalorimctric bead reactor. The nature of the support had no detectable influence on the catalytic activity during a given experiment, but was found to affect the long-term stability of the catalyst. Investigations have been made of the kinetics of the oxidation of methane over a palladium/thoria catalyst both in the absence and in the presence of the reaction products. Oxidation was found to be strongly inhibited by the water formed, which tended to cause permanent deactivation of the catalyst; there was also very slight inhibition by carbon dioxide. Measurements of the rates of co-oxidation of methane with other compounds showed that methanol reacted independently, whereas formaldehyde and carbon monoxide were both oxidized competitively. It has been shown that the reactivity of water towards the catalyst support is an important factor governing the deterioration of catalytic activity. In accordance with this there was no evidence of catalyst deactivation when methane was co-oxidized with methanol, which would be expected to displace water.