Study On The Methanation Of Biomass Syngas Catalyzed By Ni-CeO₂/?-Al₂O₃ Catalyst

Nowadays, demand of natural gas is increasing in our country. Natural gas is in short supply. In order to make up for the natural gas resources, China uses coal to prepare natural gas. But the combustion of coal will release a large amount of CO2 and the combustion of sulphide and chloride in coal will also pollute the air. As an agricultural country, our country has abundant biomass resources. Biomass is a renewable resource and it's a trend to use biomass resources to solve the problem of shortage of natural gas. Now, people always use biomass by direct combustion. But this way is low calorific value and will cause smog pollution. Therefore, the synthesis of syngas from biomass is an efficient way to use biomass. Because of the high content of CO in biomass syngas, it can't be used as civil gas. The methanation of biomass to reduce the CO content is important.In this article, Ni/Al₂O₃ catalysts modified with promoter Ce?Zr?Co?Y?V were prepared by wet impregnation method, and were used for hydrogenation of CO to methane in a fixed bed reactor. The effect of promoter content, impregnation sequence, reduction temperature, and the calcination temperature on catalyst structure and catalytic activity have been investigated. Characterization of different catalysts was carried out using BET, XRD, H2-TPR, H2-TPD, SEM. The results showed that catalysts Ni/Al₂O₃ modified with CeO2, ZrO2, Y2O3, V2O5 had better catalytic performance than Ni/Al₂O₃. The 6Ni-3CeO2/Al₂O₃ catalyst prepared by co-impregnation showed the best catalytic activity. It possessed larger specific surface area, higher Ni species dispersion, lower reduction temperature and higher catalytic activity for catalytic methanation of syngas comparing with only Ni-based catalysts. When the gas composition is V?H2?:V?CO?:V?N2? = 0.45:0.15:0.40, 6Ni-3CeO2/Al₂O₃ was calcined at 400?and reduced at 500?, it exhibited the optimum catalytic activity at 350?, 0.1MPa and 20000 h-1, the CO conversion and CH4 selectivity reached up to 100% and 90%, respectively. This catalyst can also be applied to reduce the CO content in biomass syngas to reach the standard of domestic fuel gas?CO? 10%?. And it converted partial CO to CH4 in order to improve the utilization of CO. When the feed gas was biomass syngas, the CO conversion can reach up to 80.5% and the CO content in the exhaust gas was about 6%. In this thesis, the optimized catalyst can effectively catalyze the methanation of biomass syngas in which the content of CO can be satisfied for use in domestic fuel gas.