A Cu-ZnO-Al2O3 catalyst with oxygen vacancy for efficient hydrodeoxygenation of lignin-derived guaiacol to hydrocarbons

Abstract

This study explores the efficacy of a cost-effective Cu-ZnO-Al2O3 catalyst for one-pot hydrodeoxygenation of guaiacol into hydrocarbons. Notably, complete conversion of guaiacol was achieved, yielding a 99.6% hydrocarbon over the robust Cu(6)Zn(3)Al(1) catalyst under the conditions of 4 MPa H2, 300 °C, and 8 h with a catalyst/guaiacol ratio of 0.5 g/1.0 g. In-depth catalyst characterizations unveiled the presence of oxygen vacancies within the ZnO surface layer, acting as pivotal active sites that facilitated the hydrodeoxygenation of guaiacol. Furthermore, Density Functional Theory (DFT) calculations were employed to evaluate several potential active sites, revealing that the oxygen vacancy of ZnO on the Cu surface played a crucial role. This vacancy enhanced the adsorption of intermediate cyclohexanol and markedly reduced the energy barrier for the rate-limiting step. This comprehensive investigation sheds light on the catalytic pathway and offers insights into designing efficient and sustainable biofuel production processes.