Study on the catalytic hydrodeoxygenation of lignin dimers: Adsorption properties and linkages cleavage

Production of mono-phenols through hydrodeoxygenation is one of the most promising routes for value-added lignin valorization. However, the adsorption characteristic of key intermediates and hydrodeoxygenation mechanism of key linkages in lignin have received inadequate attentions. In this paper, experiments combined with density functional theory calculations were done to explore the adsorption and catalytic HDO mechanism of lignin dimers. It was found that NiFe(1 1 1)-Mo2C(0 0 1) had a better ability on linkages activation, and showed stronger adsorption on CO containing intermediates, which was favor for further hydrodeoxygenation. Moreover, the calculation results certificated the cleavage of β-O-4 was prior to the hydrodeoxygenation of CO, and the hydrodeoxygenation of β-O-4 included a H· addition to O atom before the C-O cleavage. Finally, the elementary reactions energy barriers were efficiently reduced by NiFe(1 1 1)-Mo2C(0 0 1) catalyst during the hydrodeoxygenation reactions, which elucidated the superior performance of NiFe catalyst. This work provides a theoretical basis on efficient lignin utilization.