Study on Methanation Performance of Biomass Gasification Syngas Based on a Ni/Al₂O₃ Monolithic Catalyst

The structure of a Ni/Al₂O₃ monolithic catalyst after methanation reaction and its methanation performance were studied by taking analogue syngas of biomass gasification H₂/CO/N₂ as feed gas when the temperature ranged from 250 to 550 °C, and the weight hourly space velocity (WHSV) was between 6000 and 14,000 mL g^-1 h^-1. The Ni/Al₂O₃ catalysts using cordierite honeycomb ceramics as the substrate were prepared by dipping and sol-gel methods. The results show that the Ni/Al₂O₃ catalyst prepared by the dipping method (DIP-Ni/Al₂O₃) has better methanation performance than the Ni/Al₂O₃ catalyst prepared by the sol-gel method (SG-Ni/Al₂O₃) through many tests such as TEM, BET, XRD, H₂-TPD, H₂-TPR, and TG analysis. The DIP-Ni/Al₂O₃ catalyst exhibits the best methanation performance at 400 °C when the molar ratio of H₂, CO, and N₂ is 3/1/1 and the WHSV is 10,000 mL g^-1 h^-1. Under this condition, the CO conversion and CH₄ selectivity are 98.6 and 90.9%, respectively. In addition, the methanation performance of the DIP-Ni/Al₂O₃ catalyst is relatively more stable, and the CO conversion and CH₄ selectivity were basically maintained at around 90% within the experimental WHSV range. The influence of Ni content on the methanation performance of the DIP-Ni/Al₂O₃ catalyst can be seen in the order from high to low of methanation performance: 15% Ni, 20% Ni, and 10% Ni, and the maximum values of CO conversion and CH₄ selectivity reach 96.8 and 96%, respectively, at 400 °C for 15% Ni/Al₂O₃.