Tuning Ir-Re Bimetallic Catalyst For Glycerol Hydrogenolysis To 1,3-Propanediol

Hydrogenolysis of biomass-derived glycerol to 1,3-propanediol (1,3-PD), a highly value-added chemical usually using as a monomer to synthesize polytrimethylene terephthalate and other polymers, is an attractive alternative for petroleum based processes and thus of great significance for sustainable chemical industry.Our previous work has shown that Ir-Re alloy catalyst is an efficient catalyst for glycerol hydrogenolysis to 1,3-PD. Nevertheless, the selectivity of 1,3-PD and the reaction rate is still too low to meet the industrial requirements. The product distribution of glycerol hydrogenolysis, a structure-sensitive reaction, depends both on the catalyst structure and the reaction condition. Therefore, in this work, aiming at highly efficient Ir-Re catalyst, we focused on tuning the microstructure of Ir-Re bimetallic catalyst and their catalytic performance. The results and conclusions are as follows:1. The influence of impregnation method on the reaction characteristic of Ir-Re bimetallic catalysts was investigated. It is indicated that the scission of the C-O bond of glycerol is favored over the catalyst prepared by co-impregnation. Compared with the catalyst prepared by impregnating Ir prior to Re. the selectivity to 1,2-propanediol over the catalyst prepared by impregnating Re prior to Ir is higher. In addition, the catalyst prepared by co-impregnation and calcinated at 550℃ has lower activity.2. The effect of Ir-Re mole ratio on the alloy structure and catalytic activity of Ir-Re catalysts was studied. Highest activity is observed for 1.25 (Ir-Re mole ratio), while too much Ir on the surface of Ir-Re catalysts disrupt the Ir-Re synergy, resulting the decreased activity.3. The effect of silica surface treatment on the silica surface structure, Ir-Re structure and their activity was explored. The results indicate that the Ir-Re bimetallic catalyst loaded on the silica treated by ethanol, with the smallest particle size, has the highest activity. The interaction between silica treated by nitric acid and Ir or Re species is the strongest, which weakens interaction between Ir and Re. The partical size of Ir-Re bimetallic catalyst loaded on the silica calcinated at 450 ℃ and 850℃ is a slightly larger than the others, resulting in the decreased activity.