Enhanced fluidized bed methanation over a Ni/Al2O3 catalyst for production of synthetic natural gas

Abstract

The fluidization behavior and CO methanation performance over a typical Ni/Al2O3 catalyst for synthetic natural gas production was systematically investigated in a fluidized bed reactor. The results indicated that the methanation performance of the catalyst depends, to a large extent, on the fluidization quality in the fluidized-bed methanation reactor. The pure Ni/Al2O3 catalyst with the particle sizes of 10–100μm failed to fluid, but the fluidization can be significantly improved by adding Al2O3 particles. The methanation reaction in the fluidized bed reactor was also substantially improved by adding Al2O3 particles, and the yield and selectivity of CH4 in the fluidized bed with Al2O3 addition were much higher than those of without Al2O3 addition. The CO methanation reaction was controlled by two different mechanisms, i.e. the surface reaction controlling in lower temperature range (250–330°C) and external diffusion controlling in higher temperature range (>330°C). Stability test demonstrated that the fluidized bed methanation reactor showed higher CO conversion, CH4 selectivity and yield, and more excellent carbon resistance than the fixed bed methanation reactor under high temperature, which is beneficial for reclaiming the high temperature steam.