Elucidation of behavior of sulfur on nickel-based hot gas cleaning catalysts

A closed-loop gas-recirculation system was used to measure the isosteric he at of sulfur chemisorption on supported nickel catalysts in hot gas cleanin g conditions of gasification gas. During sulfur adsorption, reconstruction of the catalysts occurred. In addition, probably the enormous increase in s urface diffusion due to sulfur adsorption on some nickel catalysts with hig h Bow rates resulted in melt formation of adsorbed species on the surfaces of catalyst particles. Heat of sulfur adsorption on nickel decreased when s ulfur coverage was increased. However, the enthalpy of adsorption decreased even below the heat of formation of bulk Ni3S2, indicating most likely mul ti-layer or subsurface sulfur formation on catalyst surfaces. The structura l properties of the catalysts had a great influence on sulfur adsorption be havior. The effect of sulfur on ammonia decomposition in synthetic gasifica tion gas tests was explained by the change of heat of sulfur chemisorption on nickel. (C) 1999 Elsevier Science B.V. All rights reserved.