Ir-Re alloy as a highly active catalyst for the hydrogenolysis of glycerol to 1,3-propanediol

In this work, bimetallic Ir-Re catalysts supported on KIT-6 are prepared by tuning the thermal treatment procedures, i.e., conventional calcination and reduction (Ir-Re/KIT-6-CR) and modified direct reduction (Ir-Re/KIT-6-R) after impregnation of two metal precursors. The structure of both catalysts is intensively characterized by H-2-TPR, STEM-HAADF-EDX, XPS and CO-DRIFTS. Results indicate that an Ir-Re alloy forms on the KIT-6 support when direct reduction is employed, which exhibits excellent catalytic performance in hydrogenolysis of glycerol. The formation rate of 1,3-propanediol over Ir-Re/KIT-6-R reaches 25.6 mol(1,3-PD) mol(Ir)(-1) h(-1) at 63% glycerol conversion with the addition of amberlyst-15 under 8 MPa H-2, 393 K and 20 wt% glycerol aqueous solution, almost twice that over Ir-Re/KIT-6-CR. It is revealed that Re species without prior calcination treatment could be fully reduced and therefore couple with Ir to form an Ir-Re alloy structure with enhanced resistance against particle aggregation, while the calcination and subsequent reduction leads to the formation of an Ir-ReOx structure since the rhenium oxide species generated during the calcination is difficult to be reduced.