The role of Zn in the Cu-Zn-Al mixed oxide catalyst and its effect on glycerol hydrogenolysis

A series of Cu-Zn-Al oxide catalysts reduced in H2 was tested in glycerol hydrogenolysis in a stirred batch autoclave at 230C. The catalysts were prepared by the precipitation - calcination method from layered double hydroxides (LDH) structures. The oxide forms of the catalysts were obtained by calcination of these structures at programmed temperatures, up to 350C. The catalysts were characterized by the following methods: X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermogravimetric analyses (TGA), N-2-physisorption and temperature programmed desorption of ammonia (NH3-TPD). It was found that Zn plays acts as a structure modifier, influencing Cu dispersion and particle size. Consequently, Zn has an impact on the catalyst activity. In particular, the Zn effect had its maximum at the concentration corresponding to a ratio of Zn/(Cu+Al) = 0.35 where conversion of 65% and the selectivity to 1,2-propanediol of 70% was achieved after 60 min of reaction time.