LOW-LOADED PD ALPHA-AL2O3 CATALYSTS - INFLUENCE OF METAL-PARTICLE MORPHOLOGY ON HYDROGENATION OF BUTA-1,3-DIENE AND HYDROGENATION AND ISOMERIZATION OF BUT-1-ENE/

Buta-1,3-diene hydrogenation and but-1-ene hydrogenation and isomeriza tion were studied on low-loaded Pd/alpha-Al2O3 catalysts (0.1-0.3 wt.% ) prepared from palladium acetylacetonate (Pd(C5H7O2)(2)). Deuterium t racer study, hydrogen chemisorption, transmission electron microscopy, and X-ray photoelectron spectroscopy analysis were used to establish the relationships between metal-support interactions, particle shapes, and buta-1,3-diene and but-1-ene hydrogenation and isomerization mech anisms. It was found that the hydrogenation reaction rates (turnover f requencies) are similar for buta-1,3-diene and but-1-ene, but 10 times lower for the 0.1% Pd catalyst compared to the 0.3% Pd catalyst. Howe ver, the 0.1% Pd catalyst has a high activity for the isomerization re action which leads to 98% selectivity in isomers for the but-1-ene rea ction. This unusual specific activity is explained considering that th e 0.1% Pd catalyst contains flat particles in strong interaction with the support, as was deduced from several characterization methods, whi le the 0.3% Pd catalyst has more rugged bulk type particles after H-2 treatments because they are not interacting with the support. (C) 1996 Academic Press, Inc.