Syngas methanation with municipal solid waste char supported Ni catalyst: Choice of key parameters and catalyst's response

Abstract

The low quality municipal solid wastes (MSW) derived char has a potential to be used as a methanation catalyst to achieve low-cost methanation of the syngas derived from MSW, and its performance with varying reaction parameters should be explored for better application. In this study, a MSW char supported Ni-based catalyst (Ni-MSWC) was prepared by impregnation; the influences of CO2 and CH4 impurities in the raw syngas on methanation and the feasibility of conducting methanation in a low-pressure condition were investigated, then the catalyst's response to the changing parameters was identified. The results showed that the presence of low concentration CO2 in the H2-rich syngas is favorable to the gasification of the char carrier and activates Ni-MSWC catalyst. However, it also promotes F–T synthesis reaction and leads to a decrease in the methane yield (YCH4). The decrease in reaction pressure causes a decrease in YCH4 and results in coke formation; but inhibits F–T synthesis reaction and increases methane selectivity (SCH4). A higher reaction pressure increases system complexity and accelerates char carrier consumption. Moreover, presence of methane by 2.8% (vol.) promotes the methanation of CO2 through the methane dry reforming reaction, but it inevitably causes coke formation and affects the catalyst's stability. Based on YCH4 and Ni-MSWC's responses, CO:CO2 ≥ 3:2 and reaction pressure of 1 MPa (gauge pressure) are recommended, which help to inhibit the side reactions and maintain a high YCH4 (>95%).