Study on syngas methanation over municipal solid waste char supported Ni catalyst

[Display omitted] •Ni/MSWC has a higher catalytic activity than Ni/Al2O3 for syngas methanation.•Shape change of Ni particles caused decreases in CO conversion and CH4 selectivity.•Whisker carbon deposition caused decrease in CH4 selectivity.•Amorphous carbon deposition had negligible influence on CH4 selectivity. Municipal solid waste pyrolysis char (MSWC) has none suitable high-valued applications. In this research, a Ni/MSWC catalyst was prepared by loading Ni on to MSWC through impregnation for syngas methanation. Both continuous and intermittent operations were carried out to investigate activity and stability of the Ni/MSWC catalyst. Results showed that the catalyst exhibited high activity with CO conversion reaching 100%, CH4 yield higher than 100% in the beginning. SEM images of the fresh Ni/MSWC demonstrated that Ni particles were highly dispersed on the MSWC surface. In the continuous operation, the CH4 yield maintained above 90% for 29 h. In the 60 h’s intermittent operation with 10 h as a cycle, CH4 yield decreased rapidly from 102.4% in the first cycle to 78.0% at the start of the second cycle, and it decreased to around 37% at the end of the third cycle but maintained this minimum till the end; while sharp rises appeared at the start of each cycle. Decreases in CO conversion and CH4 selectivity are found to be closely related to aggregation of Ni particles, carbon deposition and collapse of the char structure. However, carbon deposition in the intermittent operation could be alleviated by N2 purging, while whisker carbon deposition was observed in the used Ni/MSWC after 39 h’s continuous operation. Highly dispersed Ni particles on the MSWC surface and proper interaction between Ni and MSWC were favorable to the activity of the catalyst, but its stability should be further improved.