High coke resistance Ni-SiO2@SiO2 core-shell catalyst for biogas dry reforming: Effects of Ni loading and calcination temperature

In this study, Ni-SiO2@SiO2 core-shell catalysts were prepared using the ammonia evaporated synthesis method, followed by encapsulation by a silica layer. The effect of nickel content and calcination temperature on the catalytic activity were separately studied in the biogas dry reforming reaction. The results revealed that the catalytic activity improved and carbon deposition increased when nickel content increased from 2.5 to 15 wt.%. Ni-SiO2@SiO2 with 10 wt.% Ni loading exhibited stable and high methane and CO2 conversions with negligible carbon formation during 12 h time on stream at 700 °C. Also, because of the high carbon resistance property of the prepared catalysts, the CH4 conversion over Ni-SiO2@SiO2 catalyst remained constant at 52% for 12 h at a low reaction temperature of 600 °C. Compared with Ni-SiO2@SiO2 core-shell catalyst, Ni/SiO2 supported catalyst fabricated by impregnation method exhibited lower activity and stability. High stability and carbon deposition resistance properties of the Ni-SiO2@SiO2 catalyst were ascribed to the strong Ni-SiO2 interaction and coverage of the Ni particles by SiO2, which make them resistant against migration and sintering. The results indicated that the catalytic activity gradually improved with the augment of calcination temperature from 600 to 800 °C. Ni-SiO2@SiO2 catalyst calcined at 800 °C with moderate nickel size and intermediate Ni-SiO2 interaction demonstrated the best catalytic activity.