Hydrogenation of lignin-derived phenolic compounds over Co@C catalysts

Co-MOF was firstly prepared by solvothermal method, and then Co@C catalyst was prepared by one-step pyrolysis method from Co-MOF. The structure of Co@C catalyst was characterized by N₂ physical adsorption-desorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Effects of Co-MOF pyrolysis temperature, reaction temperature, initial hydrogen pressure and reaction time on catalytic hydrogenation of guaiacol were investigated. The results show that both Co-MOF and Co@C are dominated by mesoporous. After pyrolysis, lamellar structure of Co-MOF changes into irregular sphericity. As raising pyrolysis temperature, specific surface area of Co@C decreases continuously. Under the conditions of reaction temperature 180 ℃, initial hydrogen pressure 2 MPa and reaction time 2 h, the guaiacol was completely transformed and selectivity of cyclohexanol was 92.8% using Co@C-600 as catalyst. The main reaction pathway of guaiacol hydrogenation catalyzed by Co@C is that guaiacol firstly forms phenol through removal of methoxyl group, and further is hydrogenated to cyclohexanol. In addition, Co@C-600 also has good catalytic activity for other phenolic monomers derived from lignin, such as phenol, p-methoxyphenol and 4-methyl guaiacol.