Waste-derived char-supported Ni catalyst for syngas methanation: Ni recovery, performance evolution and its implications for assessing char support

Syngas methanation was studied using the regenerated Ni-based catalyst supported on municipal solid waste-derived char (Ni/MSWC). Catalysts were prepared by recovering Ni from the spent Ni/MSWC via an acid-assisted process and their performance evolution was analyzed by experiments and density functional theory (DFT) calculations. The regenerated catalysts showed similar methanation activity to the original with a CH4 yield of ∼90 % but repeated acid-assisted recovery carried the risk of deactivating the catalyst, due to the enrichment of acid-soluble minerals from the char carrier. The ash composition of char carriers quantified with an alkali-carbon index of ∼20 could be an indicator for assessing the char carriers. DFT insights proved defect-induced Ni particle adsorption on MSWC and the improved electronic structure of Ni particles induced by the active acid-soluble minerals. This research highlights the potential of utilizing MSWC and recovered Ni for sustainable methanation catalysts and provides implications for choosing qualified waste-derived char carriers. [Display omitted] •Repeated Ni recovery and reuse to prepare Ni/MSWC for methanation.•The catalyst prepared with recovered Ni showed activity comparable to the original catalyst.•The number of acid-assisted recoveries depended on the char carrier’s ash content.•H-assisted CO&CO2 dissociation was determined to be the pathway for COx methanation.•Enhanced performance of catalyst due to the interactions between char components and Ni.