REFORMING OF METHANE WITH CARBON-DIOXIDE OVER NI AL2O3 CATALYSTS - EFFECT OF NICKEL PRECURSOR/

The catalytic activities of Ni/gamma-Al2O3 catalysts prepared using di fferent nickel precursor compounds were studied for the reaction of me thane reforming with CO2. It is found that the nickel precursor employ ed in the catalyst preparation plays an important role. The catalyst b ased on nickel nitrate exhibited higher catalytic activity and stabili ty over a 24-h test period than the other two catalysts derived from n ickel chloride and nickel acetylacetonate. A comprehensive characteris ation of the catalysts showed that the weak interaction between Ni par ticles and gamma-Al2O3 resulted in more active sites on Ni nitrate-der ived Ni/gamma-Al2O3 catalyst. Coking studies showed that carbon deposi tion on Ni catalysts derived from inorganic precursors (nitrate and ch loride) were more severe than on the organic precursor-derived catalys t. However, the Ni nitrate-derived catalyst was found to have the high est stability (or lowest deactivation rate) mainly due to the active c arbon species (-C-C-) of the resulting graphitic structure and their c lose contact with the metal particles. In contrast, the carbon formed on Ni-AA catalyst (from Ni acetylacetonate) is dominated by inactive - CO-C- species, thus leading to a rapid accumulation of carbon in this catalyst and more severe deactivation. (C) 1998 Elsevier Science B.V.