A STUDY ON THE DISPERSION AND CATALYTIC ACTIVITY OF GAMMA ALUMINA-SUPPORTED PALLADIUM CATALYSTS

Electron spectroscopy for chemical analysis (ESCA) and carbon monoxide adsorption techniques have been applied to study the percent exposed (i.e., dispersion) and Pd deposition in the pores of highly porous gamma alumina-supported Pd catalysts. A correlation has been found between Pd dispersion and its extent of penetration into the pores: more edge-coated catalysts are less dispersed. The dispersion of Pd is controlled by a carrier-catalyst interaction that originates in part from electron transfer from the support to the supported Pd. This electronic interaction is demonstrated by the broadening of the ESCA peaks. The activity of the catalysts, measured by the hydrogenation of nitrobenzene to aniline, is dependent on the dispersion of palladium.