Characterization and sintering of alumina-supported palladium catalysts

A comparative study of methods (H, CO and 0 chemisorption,0 and H titrations and some physical methods) for metal particle size determination in several Pd/Al0 catalysts (metal contents from 0.45to5.26%)was carried out. The results obtained strongly suggest that the H chemisorption in controlled conditions is the most accurate method. Proportions of bridged PdO and PdCO species were determined. It is proposed that the sinterization of these catalysts(in H, high vacuum and H0) between 723 and 973 K takes place by atomic migration. The rate of sintering increased in the series H< highvacuum