Methanation Performance of Biomass Gasification Syngas over Alkali-Modified Ni/Al2O3 Monolithic Catalysts
The methanation of biomass gasification syngas (H2/CO = 3:1) was investigated over Ni/Al2O3 monolithic catalysts supported on cordierite, with a nominal Ni loading of 15 wt%. Catalysts were modified by treatment with 10% NaOH solution for 1 h and 2 h. Physicochemical properties were characterized by BET, TEM, H2-TPR, XRD, CO2-TPD, and TG. Results showed that the 2 h modification (15%Ni/Al2O3-2h) increased specific surface area, enhanced catalytic activity, and increased alkaline site density compared to the unmodified catalyst. Under optimized conditions (H2/CO volume ratio 3:1, space velocity 10000 mL/(g·h), temperature 400 °C), the 15%Ni/Al2O3-2h catalyst achieved a CO conversion of 97% and CH4 selectivity of 100%. Stability tests over 2 h showed that the CO conversion remained stable at approximately 98%, indicating excellent catalytic stability. The study demonstrates that alkali modification with 10% NaOH for 2 h significantly improves both the methanation performance and stability of Ni/Al2O3 monolithic catalysts, offering a promising route for synthetic natural gas production from biomass.