Sulfur Poisoning of Nickel in co Hydrogenation

Abstract

Publisher Summary This chapter discusses the sulfur poisoning of nickel in CO hydrogenation. Poisoning of supported metal catalysts by sulfur conpounds at low concentrations is the most serious catalyst deactivation problem in methanation and Fischer–Tropsch synthesis, often reducing catalyst life to a few months or weeks. This high sensitivity is apparently because of the strong bonding between sulfur and metal surfaces making regeneration impossible or impractical. Nickel–sulfur bonds of sulfur adsorbed on nickel are significantly stronger than nickel–sulfur bonds in bulk nickel sulfides. Heats of H 2 S adsorption on nickel are 80–100% larger than heats of formation of the bulk sulfides. High sulfur concentrations reduce the amount of CO dissociation that can occur on Ni, and the carbon so produced is less reactive to hydrogenation; CO adsorption on nickel at low temperatures may be increased at sufficiently high CO pressures because of the formation of nickel subcarbonyls and tetracarbonyl. Product selectivity in CO hydrogenation is shifted by sulfur poisoning in the direction of higher molecular weight products.