ABSTRACT
The larger Pd crystallites catalyze faster hydrogenations and faster dehydrohalogenations. The smaller Pd crystallites all catalyze slower hydrogenations at about the same rate, but catalyze dehydrohalogenations at rates passing through a minimum around 60%D. Addition of a tiny amount of cadmium acetate depresses both hydrogenation, and dehydrohalogenation, but the latter to a larger extent, so selectivity for p-chloroaniline increases. Hydrogenation activities of the catalysts are shown as turnover frequencies, which are defined as the number of hydrogen molecules consumed per second per exposed palladium atom. Concentrations of aniline and p-chloroaniline were determined after hydrogen uptake ceased. The Pd/C catalyst exhibited exceptionally high activities for hydrogenation and dehydrochlorination. Generally, larger palladium crystallites present higher percentages of exposed atoms in plane sites than in either edge or corner sites.
