Abstract: Ni/Al2O3 catalysts have been prepared through either impregnation or coprecipitation methods. The effects of Ni loading, preparation method and reaction temperature on the methane catalytic decomposition have been investigated. The results indicated that 20%（mass fraction） Ni/Al2O3 of which the average particle size of Ni was about 11.25 nm showed the best catalytic performance among the impregnated catalysts. The yields of carbon for per gram Ni and hydrogen for per mole Ni on such catalyst were 15.30 g and 164 mol, respectively. On the coprecipitated Ni/Al2O3, both the catalytic activity and lifespan of catalyst were improved. The deposited filamentous carbon over coprecipitated Ni/Al2O3 was much longer and more homogeneous than that generated over impregnated Ni/Al2O3. The methane catalytic conversion on coprecipitated Ni/Al2O3（41.2% mass fraction）remained higher than 30% after running the reaction at 550 ℃ up to 350 min.

Key words: Ni/Al2O3, methane catalytic decomposition, hydrogen, carbon filaments