Selective Hydrogenation of Dimethyl Terephthalate to 1,4-Cyclohexane Dicarboxylate by Highly Dispersed Bimetallic Ru-Re/AC Catalysts.

Abstract

The fabrication of bimetallic catalysts has been taken great focus in the concept of heterogeneous catalysis due to their high efficiency and economic concerns. In this work, a series of bimetallic Ru-Re catalysts were designed and synthesized for the selective hydrogenation of dimethyl terephthalate (DMT) to 1,4-cyclohexane dicarboxylate (DMCD) under mild condition. Characterization techniques including the XRD, TEM, STEM-HAADF EDX elemental mapping, H2-TPR, and XPS were used to study the surface chemical property, the morphology, as well as the catalytic behavior of different samples. It was revealed that the monometallic Ru catalyst already has the capacity to activate and transform DMT into DMCD. Whilst the promotion effect can be optimized to a maximum with only small amount of Re, with the mass ratio of Ru/Re as 10:1. It was also revealed that the addition of Re could largely enhance the distribution of surface active metal species, facilitate the charge transfer between Ru and Re, as well as strengthen the Ru-Re synergistic interaction, which further led to the modification of the redox ability and the catalytic performances of samples. However, excessive addition of Re caused strong interaction between Ru and Re, and further limited the H₂ activation and the seasonable release of the active reducible metal species, which was responsible for the depressed catalytic performances in the presence of higher Re loading. The Ru1.25Re0.13/AC catalyst displayed the DMT conversion of 82% with DMCD selectivity of 96% under mild condition of 70 °C at 3 MPa. The specific rate of Ru1.25Re0.13/AC based on per gram of Ru was 0.44 mol·g-1 Ru·h-1.