Synthesis of nanocrystalline mesoporous Ni/Al2O3[sbnd]SiO2 catalysts for CO2 methanation reaction.

Abstract A series of nanocrystalline mesoporous Ni/Al 2 O 3 SiO 2 catalysts with various SiO 2 /Al 2 O 3 molar ratios were prepared by the sol-gel method for the carbon dioxide methanation reaction. The synthesized catalysts were evaluated in terms of catalytic performance and stability. The catalysts were studied using XRD, BET, TPR and SEM. The BET results indicated that the specific surface area of the samples with composite oxide support changed from 254 to 163.3 m2/g, and an increase in the nickel crystallite size from 3.53 to 5.14 nm with an increment of Si/Al molar ratio was visible. The TPR results showed a shift towards lower temperatures, indicating a better reducibility and easier reduction of the nickel oxide phase into the nickel metallic phase. Furthermore, the catalyst with SiO 2 /Al 2 O 3 molar ratio of 0.5 was selected as the optimal catalyst, which showed 82.38% CO 2 conversion and 98.19% CH 4 selectivity at 350 °C, high stability, and resistivity toward sintering. Eventually, the optimal operation conditions were specified by investigating the effect of H 2 /CO 2 molar ratio and gas hourly space velocity (GHSV) on the catalytic behavior of the denoted catalyst. Highlights • Nanocrystalline mesoporous Ni/Al 2 O 3. SiO 2 catalysts were prepared by sol-gel method. • Ni/Al 2 O 3.0.5SiO 2 exhibited mesoporous structure with a high BET area of 281 m2 g−1. • Ni/Al 2 O 3.0.5SiO 2 possessed the highest catalytic activity and stability in CO 2 methanation. • The increase of Si/Al molar ratio decreased the BET area from 254 to 163.3 m2 g−1. • The nickel crystallite size increased from 3.53 to 5.14 nm with an increment of Si/Al molar ratio. [ABSTRACT FROM AUTHOR]