Producing eco-methane with raw syngas containing miscellaneous gases and tar by using a municipal solid waste char-based catalyst

Abstract

Municipal solid waste pyrolysis char (MSWC) can be used as a catalyst carrier to support the synthesis of eco-methane from the syngas. In this paper, to understand the impacts of impurities in the raw syngas, the impacts of the H2/COx ratio, the H2O concentration, and the toluene concentration on methanation were investigated over a MSWC-supported Ni-based catalyst (Ni-MSWC). The varying H2/COx ratio in syngas affected CH4 and H2 concentrations in the final product. A lower H2/COx ratio corresponded to a higher CH4 concentration and a lower H2 concentration. The H2O concentration of less than 12% (vol.) in the syngas did not inhibit methanation, whereas excessive H2O was not favorable to the COx conversion; meanwhile, it destroyed the catalyst matrix by gasification. The Ni-MSWC catalyst showed a good tolerance to toluene (<100 g/Nm3), a representative of the tar. However, an excessively high concentration of toluene such as 200 g/Nm3 caused serious carbon deposition, significantly reducing CH4 yield. The introduction of H2O in 18% (vol.) in the syngas containing toluene (200 g/Nm3) alleviated carbon deposition by steam reforming of toluene; however, methanation was still inhibited. The results of this study provide guidance for the synthesis of eco-methane from the waste-derived syngas.