Support effect on the bimetallic structure of Ir–Re catalysts and their performances in glycerol hydrogenolysis

• Nature of supports exerts significant influence on the Ir–Re structure.
• Al site in supports is detrimental to the Ir–Re synergy in glycerol hydrogenolysis.
• High mobility of Re species is crucial to obtain active Ir–Re alloy catalysts.
• Acidic Al-containing materials favor the formation of isolated Ir and Re.

Comparative study was made between the bimetallic Ir–Re catalyst supported on amorphous silica-alumina (ASA) and the ones supported on de-aluminated ASA (D-ASA) to elucidate the effects of surface Al in the support on the Ir–Re structure and their catalytic behavior in glycerol hydrogenolysis. The Ir–Re interaction is greatly inhibited because of the stronger interaction between Re species and (Si-)Al-OH sites on ASA surface, resulting in the appearance of highly dispersed Re clusters and large Ir crystals after reduction. The barely synergy between the isolated Ir and Re metals in addition to the decreased metal dispersion restrains the glycerol hydrogenolysis reaction over Ir–Re/ASA. On the other hand, the retained mobility of Re species on ‘inert’ D-ASA supports offers the intimate contact between Ir and Re species and hence the formation of Ir–Re alloy catalysts after reduction, promoting greatly the synergy between Ir and Re species in glycerol hydrogenolysis.

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