X-ray Absorption Spectroscopy of Bimetallic Pt-Re Catalysts for Hydrogenolysis of Glycerol to Propanediols

Bimetallic Pt–Re nanoparticles supported on Norit carbon were effective at converting aqueous glycerol to 1,3 (34 %) and 1,2 (33 %) propanediol at 443 K under 4 MPa of H2. Results from X‐ray absorption spectroscopy and analytical transmission electron microscopy confirmed that the nanoparticles were indeed bimetallic, with a particle size less than 2 nm in diameter. The Pt LIII near edge spectra indicated that the Pt was reduced to the metallic state by treatment in H2 at 473 K, but that a partial positive charge remained on the Re. These oxidized Re species could be associated with charged Re atoms dispersed on the carbon support because spillover of H atoms from Pt was required to reduce Re in the bimetallic particles. Propanediols are produced by hydrogenolysis of glycerol over nanometer size carbon‐supported Pt–Re particles at 443 K, whereas analogous monometallic particles are inactive. X‐ray absorption spectroscopy above the Pt and Re LIII edges reveal that both metals are reduced by H2 at 473 K to form bimetallic particles. The presence of oxophilic Re in contact with Pt promoted the selective hydrogenolysis reaction.