Selective conversion of glycerol to propylene glycol over copper zine oxide/magnesium oxide-aluminium oxide catalysts

Abstract

The present study focused on improving catalytic activity and stability of CuZnO/MgO-Al2O3 catalysts for dehydroxylation of glycerol to propylene glycol. The co-precipitation method was used to prepare the MgO(x)-Al2O3(y) mixed oxide supports by varying the ratios of x:y from 5:95, 10:90, 15:85, 20:80, and 30:70. Cu and ZnO were loaded on mixed oxide supports by incipient wetness impregnation method. The catalytic activity of catalysts was tested in a packed-bed reactor at 250 °C and 500 psig under hydrogen pressure. The CuZnO/MgO exhibited the highest stability, while CuZnO/Al2O3 gave the highest catalytic activity. However, the glycerol conversion over CuZnO/Al2O3 was continuously dropped with longer reaction time. Interestingly, CuZnO /MgO (15)-Al2O3 (85) provided both high catalytic activity and stability. The TPR profiles showed that the strong metal support interaction of catalysts increased with amount of loaded MgO, resulting in well dispersed CuO grains. Compared to CuZnO /Al2O3, CuZnO /Mg0 (15)-Al2O3 (85) showed higher catalytic activity and stability when yellow grade glycerol was used as feed. In addition, the reaction stability of CuZnO/MgO (15)-Al2O3 (85) was not affected by the mixed NaOH in feedstock.