Resin-based catalysts for the hydrogenolysis of glycerol to propylene glycol

Three alkysulfonic resins were obtained by co-polymerization of 2-acrylamido-2-methyl-propansulfonic acid with N,N-dimethylacrylamide and ethylene dimethacrylate (the cross-linker), with respectively 4, 20 and 40% mol cross-linking degree (DAE 26‑4, DAE 26‑20, DAE 26‑40). These resins were employed as acidic components in physical mixtures with Ru/C (5 %, w/w) or as supports for bifunctional ruthenium and copper catalysts, to be used in the hydrogenolysis of glycerol (20 %, w/w, in water). The physical mixtures were more efficient than the bifunctional catalysts, but temperatures as high as 200 °C are required to obtain an appreciable activity. However, in view of their relatively high thermal stability in comparison with the sulfonated polystyrene-divinylbenzene ion-exchange catalysts employed so far they can withstand this temperature, while Amberlyst 70 cannot be employed above 180-190 °C. Interestingly, the catalytic systems based on physical mixtures of DAE with Ru/C resins at 200 °C are much more selective towards propylene glycol than those containing A70 are at 180 °C.