Highly effective and stable hydrogenation of dimethyl adipate (DMA) to 1,6-hexanediol (1,6-HDO) over nonnoble metal-based catalysts under relatively mild reaction conditions was quite attractive, yet challenging. Herein, a series of Cu-based catalysts with tunable acid–base sites were developed for the hydrogenation of DMA to 1,6-HDO. Among them, the CuMgAl hydrotalcite-derived Cu–35Mg45AlO catalyst was proven to be the most effective catalyst. Under relatively mild reaction conditions (190 °C and 5 MPa), DMA conversion of 99.0% with 1,6-HDO selectivity of 97.6% was achieved. Moreover, negligible deactivation was observed over a long-term (432 h) stability test. Characterization results revealed that the spatial segregation of the hydrotalcite structure and the interaction between Cu species and MgAl2O4 spinel are responsible for the highly dispersed and stable Cu species. The synergistic mechanism of Cu0, Cu+, and weak acidic sites was proposed to play a crucial role in DMA hydrogenation, and the promotional role of acid and base sites was also disclosed.
Liu et al. (Thu,) studied this question.