Highly Exposed Co/CoOx Catalyst on Carbon Support for Efficient Hydrodeoxygenation of Lignin into Renewable Fuels

Selectively converting lignin, a renewable and abundant biomass resource, into high-value-added chemicals via hydrodeoxygenation (HDO) is a promising strategy for addressing global energy shortages and advancing sustainable practices in the agricultural and forestry industries. However, the catalytic performance of cobalt on carbon-based catalysts, particularly those prepared through pyrolysis, is often significantly hindered by the formation of carbon-coated structures that limit their activity. In this study, we developed a novel bifunctional catalyst, the redox catalyst, O-4Co/TA-600, featuring highly exposed Co/CoOx sites specifically tailored for the HDO of lignin and its model compounds. Experimental results demonstrated that tetracycloacetate-based O-4Co/TA-600 effectively cleaved various ether bonds and removed alcohol hydroxyl groups during the HDO process, achieving high alkane selectivity. The exceptional catalytic performance of O-4Co/TA-600 was attributed to the highly accessible active Co/CoOx sites and the synergistic effects between metallic Co and the acidic sites provided by CoOx, which enhanced substrate adsorption and facilitated active hydrogen (H*) generation. The catalyst retained its superior HDO activity toward diphenyl ether (DPE) after 11 reuse cycles, showcasing its excellent stability and reusability. When applied to enzymatic lignin and commercial calcium lignosulfonate, the catalyst achieves alkane selectivities of 97.6 and 92.6%, respectively. This study demonstrates a sustainable and efficient strategy for converting lignin into a feedstock for valuable chemicals and renewable fuels, thereby promoting biomass utilization in green industrial processes.