Promoting methane-rich biofuels production from gasification of biomass through direct methanation coupled with catalytic cracking of tar

Abstract

Production of methane from biomass syngas is generally water-intensive due to the need to increase the H/C ratio through the water-gas shift reaction. Herein, after gasification of rice husk upstream, the syngas with low H/C ratio was utilized through direct methanation downstream to produce methane-rich biofuel without prior water-gas shift reaction for cost saving. After coupling the tar cracking reaction upstream to adjust the H/C ratio and the content of steam and tar, the performance of direct methanation was significantly enhanced. The CO conversion rate and CH₄ growth rate increased from 61.4 % to 110.7 %–94 % and 139.2 %, respectively, when the ratio of biomass to tar cracking catalyst was set at 1:1. Characterization results revealed that the addition of the tar cracking catalyst also reduced the formation of amorphous coke downstream, thereby improving the stability of the methanation catalyst. These findings suggest that coupling tar catalytic cracking with syngas direct methanation is a promising strategy to improve the quality of syngas.