A catalytic route to lower alcohols from glycerol using Ni-supported catalysts

Abstract

The activity of Ni-supported catalysts on silica and alumina was studied for the transformation of glycerol to lower alcohols, primarily 1-propanol and ethanol. Pressure had a small effect on glycerol conversion whereas temperature had a significant effect on conversion and selectivity. Ni/SiO₂ gave quantitative conversion of glycerol at a lower temperature compared to Ni/Al₂O₃. Ni/SiO₂ also gave a higher selectivity to ethanol and propanol (63%) compared to Ni/Al₂O₃ (52%) at a similar conversion. The higher activity of Ni/SiO₂ can be ascribed to its smaller crystallite size ascertained from XRD analysis. The Ni/SiO₂ catalyst also showed improved reducibility compared to Ni/Al₂O₃. The used catalyst showed sintering of the Ni, which was confirmed by a loss of surface area and average crystallite size. The route to lower alcohols from glycerol is proposed to occur via1,2-propanediol. Biomass is readily converted into biodiesel and glycerol and we have developed a route to convert glycerol into lower alcohols. We have therefore demonstrated that it is possible to convert biomass into biodiesel and lower alcohols (viaglycerol) from the same crop, thus reducing the need to produce ethanol from a separate government-subsidised crop.