The key role of Co electron density in regulating guaiacol hydrodeoxygenation pathways over Co-Zn catalysts

The hydrodeoxygenation (HDO) of lignin-derived guaiacol offers an alternative to fossil-based routes for cyclohexanol production. However, the guaiacol HDO involves multiple parallel and sequential reactions, making the control of reaction pathways particularly challenging. In this work, Co-Zn-based HDO catalysts were synthesized using layered double hydroxide (LDH) as a precursor. The Co particle size decreases and electron density increases, while oxygen vacancy (Ov) concentration rises compared to monometallic Co, yielding higher activity and cyclohexanol selectivity. Most importantly, kinetic study reveals that electron density of Co plays a determining role in governing the HDO pathway. The guaiacol hydrogenation mainly follows two pathways over the Co-based catalyst: guaiacol → phenol → cyclohexanol (Pathway Ⅰ) and guaiacol → phenol → cyclohexanone → cyclohexanol (Pathway Ⅱ). Electron rich Co facilitates C aryl -OCH 3 bond cleavage of guaiacol to form phenol. It also selectively enhances adsorption and hydrogenation of aromatic ring while keeps the hydroxyl group intact as confirmed by the DFT calculations, favoring conversion of phenol to cyclohexanol (Pathway Ⅰ) rather than cyclohexanone (Pathway Ⅱ). These findings provide theoretical guidance for the rational catalyst design and regulation of reaction pathways in guaiacol hydrodeoxygenation.