Deactivation of catalysts by chemical poisons : final report

The hydrogen sulfide poisoning of nickel metal catalyst used in the methanation reaction of carbon monoxide and hydrogen was studied in a gradientless continuous stirred-tank reactor (CSTR). The results were modeled using the Infected Zone Model (IZM) developed by Lau (1) such that the deactivation of the catalyst can be predicted. Nickel foils and “egg-shell” supported catalysts were used in the study to minimize internal diffusional effects. The hydrogen sulfide concentration was in the low ppb level. The nickel foil catalyst exhibited an deactivation characteristics which followed IZM prediction quite well, however, the hydrogen sulfide concentration in the reactor deviated from prediction. On the other hand, “egg-shell” catalyst fared worse, the possible reasons could be the existence of internal diffusion in pores of the “egg-shell” catalyst and support effects. To continue the development of IZM, a physical interpretation of the parameter δo used in the model was made and presented. Since very low hydrogen sulfide concentration was routinely measured in the study, a procedure was developed to passivate the absorption/desorption problems associated with hydrogen sulfide, thus allowing the detection of this compound with good reliability and accuracy