Experimental Study Of Catalytic Hydrogenolysis Of Glycerol Into Propanediol With Cu-Based Catalysts

With the development of the biodiesel industry byproduct glycerol market is already saturated, high-value-added utilization of glycerol can further promote the development of bio-diesel and related industries.Therefore, it is significant to study the hydrogenolysis of glycerol to produce valuable propylene glycol.In this paper, the performance of glycerol catalytic hydrogenolysis under different acidic and alkaline conditions has been studied with Cu-based catalysts prepared by incipient impregnation method in a stainless steel autoclave. The effects of different properties of the carrier, proton acid additives, modified solid acid catalyst, catalyst preparation method and reaction conditions etc. in the catalytic hydrogenolysis have been systematically investigated. Meanwhile, we have studied the glycerol hydrogenolysis with Pt-based catalyst as a comparison.First, the Cu-based catalysts with supporter γ-Al2O3, SiO2, SiC and MgO were investigated. The highest glycerol conversion rate of 31.4%and the1,2-PD selectivity of64.3%were achieved with MgO as supporter, but much byproduct was generated at the same time. And the other three catalysts gave a relatively good catalytic activity and selectivity for1,2-PD which closed to selectivity of90%, but only with the acidic supporter SiO21,3-PD was generated which the selective was1.5%. Second, the glycerol hydrogenolysis in an acidic media was studied. It was shown that by adding H2SO4(B acid) which the amount was n(H+):n(Cu)=1:1as a substrate solution additive,1,3-PD was promoted, but meanwhile some side reactions happened and led to a substantial reduction of the selectivity of1,2-PD. Third, the Cu-based catalyst modified by proton acid which containing tungstic was investigated. The addition of phosphate tungstic acid improved the catalytic activity of glycerol hydrogenolysis and promoted the selectivity of1,3-PD. On the other hand, similar side reactions occurred, too. And they weakened with the increase of catalyst calcination temperature, because more and more phosphate tungstic acid was possibly decomposed and the acidity of the supporter decreased. At last the mechanism of glycerol reaction with Cu-based catalyst in the presence of proton acid and the corresponding thermodynamic calculations was analyzed, and we give the reason of side reactions.