Catalytic partial oxidation of methane to syngas over Ca-decorated-Al2O3-supported Ni and NiB catalysts

One wt% Ni and 1 wt% NiB catalysts supported on Ca-decorated γ-Al2O3 (Ca-AlO) supports were prepared by conventional impregnation and chemical reduction methods. These supported catalysts were applied for the catalytic partial oxidation of methane (POM) to syngas. The two low-Ni-loading catalysts have shown high activity/selectivity for the POM, as good as those of 1 wt% Rh and 10 wt% Ni catalysts supported on commercial γ-Al2O3 support (AlO). But their coking resistivity was remarkably better than that of 10 wt% Ni/AlO. The coke formation over these catalysts decreased in the following order: 10 wt% Ni/AlO ≫ 1 wt% Ni/Ca-AlO > 1 wt% NiB/Ca-AlO ∼ 1 wt% Rh/AlO. The key factor in the improvement of the carbon resistance was to decrease the metallic Ni particle size through the lowering of Ni loading combined with the addition of B promoter. The low Ni loading has been achieved by covering the support with a CaAl2O4 layer, and decreasing the catalyst calcination temperature to ∼723 K. The formation of crystalline carbon was greatly suppressed on the NiB catalysts due to the highly dispersed nature; such formation significantly improved the thermal stability of the Ni particles.