Catalytic Hydrogenolysis Of Glycerol To 1,2-propanediol Over Cu/B/Ca/Al₂O₃ Catalysts

The CaO and K2O modified catalysts Cu/B2O3/CaO/Al2O3 and Cu/B2O3/K2O/CaO/Al2O3 were prepared by impregnation-combustion method,and the influence of additives was investigated.It found that the addition of CaO can improve the performance of hydrogenolysis of glycerol remarkably.The optimal mass fraction of CaO in the support is 15%.The structure and acidity of catalyst were changed by calcium oxide.The catalysts were characterized by BET,XRF,XRD,H2-TPR,NH3-TPD and CO2-TPD.The results showed that pore volume and active sites were increased with the addition of CaO,and its alkalinity is increased with the addition of CaO and K2O.The catalyst 15Cu-5B-15CaO-Al2O3,with a weight loading of 5%B2O3 and 15%of copper and 15%CaO of support,was developed.High yield(>97%)of propylene glycol was obtained with 100%conversion of glycerol under condition of low WHSV of 0.7 h-',240 ?,n(H2)/n(GL)?8.5 and 5.0 MPa hydrogen pressure.The stability of catalyst and mechanism of deactivation were investigated in this paper.The catalyst Cu/B/K/Ca/Al showed the high initial glycerol conversion and selectivity of propylene glycol for 300 h,and the conversion of glycerol declined to 92%within a few hours.Increasing the temperature and reducing space velocity of glycerol could improve the glycerol conversion to 98%and 99%,respectively.Cyclohexane,which could form an azeotropic system with water of product,was added to the reaction.It found that the catalyst durability was prolonged,which meant cyclohexane could change hydrothermal environment.Characterization results such as BET,XRD,XRF,TG-DTA,showed that surface area and calcium oxide were decreased,but copper content did not show obvious change after long time reaction.The deactivated catalyst regenerated by air calcination exhibited an initial glycerol conversion of 99.5%.The surface area and copper particle dispersion were increased.The macro kinetics of the glycerol hydrogenolysis was also studied,with the apparent activation energy,and reaction order of glycerol estimated to be 89.29 KJ/mol,-1.34,respectively.