DEACTIVATION OF NICKEL-CATALYSTS BY SULFUR-COMPOUNDS .1. BENZENE HYDROGENATION

Deactivation by sulfur compounds was investigated on nickel catalysts in the course of benzene hydrogenation at low temperatures (323-423 K). The various poisons were injected by pulses and were characterized by their "initial toxicity" T(i). The "initial toxicity" depends strongly on both the nature of the sulfur compound and the nature of the catalyst. It appears that T(i) is least when the sulfur compound adsorbs more dissociatively. Thus, such poisons are less toxic on the more hydrogenolyzing catalyst and T(i) follows the sequence T(ithiophene) almost-equal-to T(ithiolane) > T(i)C3H7-SH almost-equal-to T(i)C6H13-SH > T(i)H2S. Nevertheless, such an explanation cannot account for the different toxicities of H2S on the various nickel catalysts. A complementary explanation is given in the following paper.