EFFECTS OF SINTERING ON THE ACTIVE-SITE DISTRIBUTION ON PROMOTED CATALYSTS

Perhaps the most important property of any catalytic system in the applied context is the magnitude of the catalytic decay with time on stream. Even though this is the case it is very much more common for fundamental catalytic research to concern itself with the features of initial catalyst performance. In this paper the effects of catalyst sintering on catalytic behavior are considered for the case where the catalyst has been doped with a promoter to enhance its initial performance. Two mechanisms of sintering are considered - coalescence and Ostwald ripening. It is shown that the long term effect of promotion is strongly dependent on the surface level of the promoter and that promotion can lead to very different decay rates of activity with time than for the unpromoted case, showing both greatly increased, and reduced rates of decline depending upon the mechanism of sintering and the range of the promoter action.