SULFUR POISONING OF NICKEL METHANATION CATALYSTS .1. INSITU DEACTIVATION BY H2S OF NICKEL AND NICKEL BIMETALLICS

The effects of exposure to dilute H2S during reaction on the methanation activity of alumina-supported nickel, cobalt, and nickel bimetallic catalysts in powder, pellet, and monolith form were investigated. Results of activity tests at 525 °K, 1 atm, and a space velocity of 30,000 hr-1 with 10 ppm H2S in the reactant stream show that cobalt and most nickel bimetallic catalysts are not significantly more or less sulfur tolerant than nickel; Ni-MoO3, however, is more active before, during, and after exposure to H2S. The data also indicate that monolithic catalysts are significantly more sulfur resistant than either powder or pellet catalysts. All of these catalysts, however, are completely deactivated within a period of 2-3 days under the conditions investigated. During reaction in the presence of H2S, there is an exponential decrease in activity accompanied by a gradual breakthrough of the poison. Less sulfur is adsorbed on the catalyst during reaction than would be if equilibrium adsorption occurred. Data showing the roles of temperature, gas composition, and catalyst geometry in the poisoning process and the results of regeneration experiments are presented and discussed. © 1979.