Abstract:The sol-gel method was used to synthesize nickel-alumina catalysts with various nickel loadings. Chemical and physical properties of support and supported nickel were characterized by TGA, DTA, EDX, SEM, BET, XRD and TPR techniques. Calcination temperature (500 • C) was determined by performing thermogravimetric analysis (TGA) and differential thermal analysis (DTA) on the samples. Energy dispersive X-ray (EDX) was used to determine the actual content of nickel on alumina. N 2 adsorption test revealed that the specific surface area varied between 550 and 223 m 2 /g for pure alumina and 30%Ni/Al, respectively. X-ray diffraction (XRD) patterns showed no peaks due to NiO species and NiO species were well dispersed on the support by formation of NiAl 2 O 4 phase. Temperature-programmed reduction (TPR) indicated that the nickel species mainly presented in NiAl 2 O 4 phase and small amount of NiO. In the 20 percent nickel loading, the surface NiAl 2 O 4 phase, which is between NiO and bulk NiAl 2 O 4 phases in terms reducibility, was formed considering as a successful result.

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Ni/Al2O3 catalysts were synthesized by sol-gel method with various nickel loadings. Chemical and physical properties of the catalysts were characterized by XRD and TPR techniques. X-ray diffraction patterns showed no peaks due to NiO species. Temperature-programmed reduction (TPR) indicated that the nickel species mainly presented in NiAl2O4 phase. The effect of nickel loading on the catalytic activity of Ni/Al2O3 catalysts, selectivity of products, yield of hydrogen production and H2/CO ratio was investigated in the combination of dry reforming and partial oxidation of methane (DRPOM) reaction. The results indicated that these parameters are greatly dependent on the amount of nickel loading. The results also revealed that the catalyst with 20 percent nickel loading had the highest activity for syngas production after 270 min reaction on stream. The SEM images of spent catalysts showed the formation of filamentous carbon on the 20Ni/Al and 30Ni/Al catalysts.