Efficient Hydrogenation of Methyl Palmitate to Hexadecanol over Cu/m-ZrO2 Catalysts: Synergistic Effect of Cu Species and Oxygen Vacancies

Abstract

Renewable fatty esters are a class of clean feedstock to produce high value-added fatty alcohols. Herein, the hydrogenation of methyl palmitate (MP) to hexadecanol over defect-rich Cu/m-ZrO2 catalysts was studied systematically. A series of Cu/m-ZrO2 catalysts with different concentrations of oxygen vacancies (Ovs) were fabricated by adjusting the calcination temperature of m-ZrO2 support. Among the catalysts, Cu/m-ZrO2-350 displays the highest Cu dispersion, the largest number of Cu0 sites and surface Ov concentration, which exhibits the best activity for MP hydrogenation. It gives the MP conversion of 94.6% and hexadecanol yield of 93.3% at 300 °C and 7.5 MPa of H2. Spectroscopic characterizations and theoretical calculations revealed that the highly dispersed Cu species and abundant Ov sites synergistically boost the hydrogenation of MP. Specifically, the Cu0 sites facilitate the heterolysis of H2, and the Ov sites contribute to the dissociation of MP. The synergistic effect of Cu species and Ov sites disclosed in this work provides deep insights into the design of catalysts for efficient conversion of fatty esters to fatty alcohols.