INFLUENCE OF CALCIUM ON THE CATALYTIC BEHAVIOR OF NICKEL IN LOW-TEMPERATURE HYDROGASIFICATION OF WOOD CHAR

Demineralized birch char co-loaded with nickel and calcium was hydroga sified to examine the catalytic behavior of the binary system at tempe ratures below 700 degrees C. The activity of nickel was determined by the amount of coexisting calcium, and it became a maximum at a given r atio of calcium to nickel. This can be explained by the two roles of c alcium: (1) retardation of nickel sintering and (2) inhibition of the formation of catalytically active nickel species. Calcium was consider ed to interact with nickel to form a certain double oxide of calcium a nd nickel, whereby both actions occur. On the basis of this assumption , the function of calcium for nickel-and iron-catalyzed hydrogasificat ions of wood char is discussed. (C) 1998 Elsevier Science Ltd. AII rig hts Reserved.