Sulfurization and regeneration of platinum

Abstract

Chemisorption of H 2S on Al 2O 3 supported platinum is dissociative and hydrogen is observed in the gaseous phase. Above 100°C, platinum surface atoms are fully covered by sulfur atoms. Hydrogen treatment at 400°C partly restores the catalytic and chemisorptive properties of platinum towards benzene hydrogenation and adsorption of carbon monoxide in the linear form. Adsorptions or reactions requiring polyatomic sites (n-butane hydrogenolysis, chemisorption of CO in bridged form) are still inhibited. Oxygen treatments of the poisoned catalyst, followed by hydrogen reduction under mild conditions, fully restore the properties of the starting material. Sulfur removal from platinum occurs with the formation of sulfate groups bonded to the support. Under more severe conditions of reduction, the reductio the sulfate groups leads again to a poisoning of the metal surface.