Dispersion stability and methylcyclopentane hydrogenolysis in Pd/Al2O3 catalysts

Pd/Al2O3 catalysts with different palladium contents and precursor salts have been submitted to a reduction-oxidation cycle and their dispersions have been measured. The catalysts presented a decrease in dispersion, except for the catalyst with 1 wt.% Pd prepared with PdCl2, which remained constant. The presence of complex species of palladium and chlorine, identified by diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) analyses, can be responsible for the stability of the dispersion. The precursor salt affected the activity and selectivity in the methylcyclopentane reaction, but the selectivity was rather constant for different palladium contents in the catalysts prepared with PdCl2. These last catalysts also showed hydrocracking reactions, attributed to the significant content of residual chlorine. These reactions changed considerably the distribution of the methylcyclopentane hydrogenolysis products compared to the literature. The catalyst with 1 wt.% Pd, prepared with Pd(NO3)(2), showed less activity and a distinct distribution of the products, in which no light products were observed. (C) 2000 Elsevier Science B.V. All rights reserved.