The selective hydrodeoxygenation of guaiacol to cyclohexanol over cobalt-modified TS-1 catalysts

A Co-modified zeolite (Co/TS-1) catalyst is prepared and evaluated for the catalytic hydrodeoxygenation (HDO) of the lignin-derived model compound guaiacol under mild conditions at 1 MPa H2 and 200 °C. According to the systemic experimental investigations including reduction temperatures, metal loading and reaction time, it is found that the guaiacol conversion and cyclohexanol selectivity over guaiacol HDO are significantly improved by regulating the Ti content, Co content and reduction temperature, in which 5.0%Co/TS-1 (Si/Ti = 110) reduced in 600 °C shows the superior HDO performance with 94.3% guaiacol conversion and 88.7% cyclohexanol selectivity. Combined with XRD, TEM, BET, NH3-TPD, Py-IR, H2-TPR, UV–Vis and XPS characterizations, it is confirmed that the introduction of appropriate Ti could modulate the catalyst Lewis acid sites and the interaction between Co and support to affect the metal reduction degree, to realize the improvement of the substrate adsorption and exposing more metallic Co0 active sites, resulting in higher HDO performance. In addition, the reaction pathway of guaiacol HDO to cyclohexanol over Co/TS-1 is proposed via demethoxylation of guaiacol to generate reaction intermediate phenol.