Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol over Hydrotalcite Derived Mg2Al1–xFexO: Role of Surface Basicity

Abstract

Hydrotalcite-derived MgAl oxides, known for their acid-base bifunctional properties, have gained substantial interest as catalysts in heterogeneous reactions. In this study, we synthesized Mg₂Al_1–xFe_xO catalysts by thermally decomposing layered double hydroxides (Mg₂Al_1–xFe_x–LDH) at 400°C. The results showed that the Fe substitution reduced the acidity, while enhancing the basicity, of Mg₂Al_1–xFe_xO, providing a way to adjust the acidity and basicity of materials for specific reactions. Catalytic transfer hydrogenation (CTH) of furfural to furfuryl alcohol, with isopropanol as hydrogen donor, was applied to evaluate the catalytic performances of Mg₂Al_1–xFe_xO. Mg₂AlO, Mg₂Al_0.8Fe_0.2O and Mg₂Al_0.5Fe_0.5O exhibit comparable catalytic hydrogenation activities, despite the progressive decrease in surface acidity and the corresponding increase in basicity. To elucidate the contributions of acid and base sites to the CTH process, poisoning experiments were carried out to passivate them by adding pyridine or benzoic acid to the reaction, which suggests that the evolution occurring on the base site is the rate-determining step of the reaction. Effect of reaction conditions on the activity of Mg₂Al_0.5Fe_0.5O were investigated, and a reaction mechanism was proposed, to reveal the reaction nature.