Dry-Oxidative Reforming of Biogas for Hydrogen Generation over Ca and Mg-Promoted Titania-Supported Nickel Catalyst

Hydrogen is gaining significant interest from researchers because of its renewable and clean nature. In this study, we explored the effects of promoters and oxygen addition on biogas reforming. The promotion of catalysts with alkaline earth metals (Ca and Mg) improved the basicity of the catalyst, leading to enhanced catalytic activity and stability. The promotion of the Ni/TiO2 catalyst with Ca showed higher CH4 conversion and H2 yield compared to the bare and Mg-Ni/TiO2 catalysts. The enhanced activity of Ca-Ni/TiO2 could be attributed to its high dispersion, small particulate size, and strong metal–support interaction. Adding oxygen to the reactor feed improved the activity and stability of the catalyst due to the simultaneous occurrence of dry and partial oxidative reforming. The maximum CH4 conversion and H2 yield of 81.13 and 37.5% were obtained at 800 °C under dry reforming conditions, which increased to 96 and 57.6% under dry-oxidative reforming (O2/CH4 = 0.5). The CHNS analysis of the spent Ca-Ni/TiO2 catalyst also showed carbon deposition of only 0.58% after 24 h of continuous dry-oxidative reforming compared to 25.16% under continuous dry reforming reaction. XRD analysis of the spent catalyst also confirmed the formation of carbon deposits under dry reforming. Adding oxygen to the feed resulted in the simultaneous removal of carbon species formed over the catalytic surface through gasification. These findings demonstrate that Ca promotion combined with oxygen addition significantly improves the catalyst efficiency and durability, offering a promising pathway for stable, long-term hydrogen generation. The results highlight the potential of Ca–Ni/TiO2 catalysts for integration into biogas reforming units at an industrial scale, supporting renewable hydrogen production and carbon mitigation in future energy systems.