CATALYTIC COMBUSTION OF METHANE OVER SUPPORTED PALLADIUM CATALYSTS .2. SUPPORT AND POSSIBLE MORPHOLOGICAL EFFECTS

The effect of using various precursor palladium salts and different support materials in the preparation of palladium catalysts for methane combustion has been investigated. Catalyst activities were found to increase dramatically after heating in a 1% CH4/air reaction mixture. These activation effects were altered according to the precursor salt and support material used. The activation of silica samples occurred over short time periods (minutes-hours) whilst the activation over alumina was more prolonged (up to 8 days). Many experimental factors which could be responsible for the activation were investigated and are discussed, but none were found to be of paramount importance in initiating catalyst activation. Reconstruction of the palladium oxide crystallites is proposed as a cause of catalyst activation. Possible mechanisms for this reconstruction are considered. It appears that only a small fraction of the palladium surface is active for methane combustion. © 1990.