Highly active and stable Cu-MnO/SBA-15 catalyst for hydrogenation of acetic acid to ethanol: Experimental and DFT studies

Copper as a non-noble metal catalyst has great prospects in the hydrogenation of acetic acid to ethanol. In this paper, Cu-MnO/SBA-15 catalysts with highly catalytic performance and stability were prepared. The mechanism was elucidated by experiments and DFT calculations. The Cu and MnO were coexistent on reduced x Cu y Mn/SBA-15. Appropriate Cu/Mn ratio was beneficial for increasing the Cu surface area and reducing the size of Cu. The rate-controlled step was found and the MnO could effectively lower the difficulty of acetaldehyde formation by dioxyethylidene. DFT calculations indicated that the formation of ethyl acetate at the Cu-MnO interface was largely prevented. The optimal catalytic hydrogenation activity was obtained for 9Cu1Mn/SBA-15, with the conversion of acetic acid and selectivity of ethanol of 99.9% and 90.1%, respectively. The catalytic activity could remain within 72 h which was more stable than the original Cu-based catalyst. • Ethyl acetate was mainly formed by the combination of acetyl and ethoxy. • MnO was beneficial to increase the surface area of Cu, thereby promote the hydrogenation of acetaldehyde to ethanol. • The activation energy barrier for the formation of ethyl acetate increased significantly. • MnO could effectively increase acetaldehyde formation by dioxyethylidene. • At 2.5 MPa and 350 °C, the acetic acid conversion and ethanol selectivity reached 99.9% and 90.1%, respectively. Cu-Mn/SBA-15 remained its activity within 72 h.