Controlling the selectivity of supported Ru nanoparticles during glycerol hydrogenolysis: C−O vs C−C cleavage

Controlling the selectivity of a reaction by rational designing of catalyst is an important and challenging topic in catalysis research. In this article, we report a strategy to tune the product selectivity during aqueous phase hydrogenolysis of glycerol using gaseous H2. Ru/TiO2 is an active catalyst for the hydrogenolysis of glycerol, however it promotes the hydrogenolysis of C−C bonds resulting in large quantities of C2 and C1 products. On the other hand, Pd/TiO2 and Pt/TiO2 catalysts are very selective for the hydrogenolysis of C−O bonds producing mainly C3 products (1,2 and 1,3 propanediols), however they are much less active compared to the Ru catalysts. In this article, we report that by combining Ru with Pt or Pd in a bimetallic nanoparticle, we can develop new catalysts that are both active and selective for C−O hydrogenolysis. A physical mixture of two monometallic catalysts does not show this enhanced selectivity for C−O hydrogenolysis, proving that intimate mixing of the two metals in a nanoparticle is crucial to tune the selectivity. All the monometallic and bimetallic catalysts have been characterised by microscopic and spectroscopic methods to understand their structural features. DFT studies were also done to rationalise the observed difference in the catalytic properties between monometallic and bimetallic catalysts