Enhanced steam gasification of lignin to generate H2-enriched syngas over a (Ni-Ce)/CaO catalyst

The utilization of industrially generated lignin is an important aspect of achieving worldwide carbon neutrality. In this study, Ni/CaO, Ce/CaO and (Ni-Ce)/CaO catalysts were prepared using an impregnation method to improve the production of H₂-enriched syngas from lignin steam gasification. Results show that the Ni/CaO and Ce/CaO exhibited different effects when applied to steam gasification, the former improved the conversion of solid lignin whereas the latter promoted decomposition of the resulting volatiles. The (Ni-Ce)/CaO catalyst provided a remarkable synergistic effect on production of H₂-enriched syngas. The mass-based yield of gaseous products and the volume-based proportion of H₂ in these products were respectively 70.8 % and 61.1 % in the presence of the (Ni-Ce)/CaO catalyst with a Ni-to-Ce molar ratio of 1:0.9. The H₂ yields obtained from this material were found to gradually decrease from 763 to 681 mL/(g lignin) during five repeated uses. This gradual deactivation of the (Ni-Ce)/CaO catalyst was ascribed to both carbon deposition and the formation of CaSO₄ by reactions between sulfur in the lignin ash and the CaO component.