Catalytic dehydroxylation of glycerol to propylene glycol over copper zinc oxide/magnesium oxide catalysts: effect of catalyst preparation

Abstract

The present study focused on improving the stability of the catalyst in the presence of an alkali for dehydroxylation of glycerol to propylene glycol. The CuZno supported on the basic support MgO was investigated in this work. The catalysts were prepared by two different methods-incipient wetness impregnation (IWI) and co-precipitation (COP). Catalytic activity was tested in a packed-bed reactor at 250 °C and 500 psig under hydrogen atmosphere. The co-precipitated catalyst showed higher glycerol conversion and propylene glycol selectivity than the impregnated catalyst. This might be due to the well dispersed and uniform CuO grains in the co-precipitated catalyst. Moreover, AAS results indicated that the co- precipitated catalyst had higher amounts of active sites (Cu) than the impregnated catalyst. The effect of NaOH containing feedstock was also investigated. The results showed that NaOH did not affect stability of the CuZnO/MgO catalysts as compared of the previously investigated CuZnO/Al2O3 catalyst. Moreover, it also enhanced the basicity of the catalyst in the presence of MgO and led to higher catalytic activity Interestingly the glycerol conversion of the regenerated CuZnO/MgO catalyst prepared by COP was as high as that of the fresh catalyst.