STRUCTURE SENSITIVITY OF METHANATION ON NICKEL

In the present work we demonstrate that the methanation activity of the flat Ni(110), Ni(100) and the periodically profiled Ni(110) surfaces increases by 100-200% gradually in the first few hours of the reaction at 500°C. AES measurements and the investigation of CO and H2 adsorption-desorption after the reaction revealed that neither the surface chemical composition nor the area increase of the surfaces are responsible for the enhanced activity. Immediate evidence for a surface restructuring is available only for the profiled Ni(110) surface, but possibly on all of the surfaces the increase in activity is due to microscopic scale restructuring. It was also detected that, during the early period of the reaction, the segregation of the sulphur is markedly increased. From a catalytical point of view our results reveal that the poison role of surface sulphur may manifest itself not only in decreasing the methanation rate but also in inhibiting the structural transformation. © 1990 Pergamon Press plc.