Modification of Cu–ZnO–ZrO2 catalysts with La2O3 to quantitatively tune Cu+–Cu0 dual sites for hydrogenation of dimethyl adipate to produce 1,6-hexanediol

Abstract

Efficient and selective hydrogenation of dimethyl adipate with Cu-based catalysts is an important step. Herein, we synthesized a series of Cu–ZnO–ZrO₂–La₂O₃ catalysts for DMA hydrogenation. The CZZ-L2-CP catalyst presented the highest catalytic activity. The CZZ-L2-CP catalyst has more oxygen vacancies, and the electron density of surface La₂O₃ species has decreased. Moreover, the electron donor–acceptor interaction between lanthanum and copper species prevented the formation of larger copper particles. In addition, the presence of La₂O₃ can inhibit the transition from Cu₂O to Cu, maintaining a relatively constant ratio of Cu⁺/(Cu⁰ + Cu⁺). Besides, the effects of different addition methods of La on the hydrogenation performance of DMA were also studied.