Preparation And Modification Of Supported Raney Cu/Al₂O₃ Catalyst On Hydrolysis Of Glycerol To 1,2-Propylene Glycol

Waste fat from animals and plants can be converted into biodiesel by interesterification.In recent years,biodiesel as a renewable energy has developed rapidly,its large by-product glycerol needs to be converted into high added value chemicals?1,2-PDO?,which improve the comprehensive utilization efficiency of biomass resources.The preparation and modification of catalyst with Raney Cu as active component were explored.The catalysts were characterized by SEM,XRD and H₂-TPR.Catalytic activity and 1,2-PDO selectivity for glycerol hydrogenolysis were evaluated in batch and fixed bed reactor,the activity stability,deactivation cause and catalyst regeneration were studied,which has certain guide for the development of glycerol hydrogenolysis to1,2-PDO.Firstly,the catalytic performance of Raney copper catalyst for glycerol hydrogenolysis to 1,2-PDO and the effect of solvent and metal oxides were studied.The results show that polarity of solvents has a significant effect on the activity of catalysts and the selectivity of1,2-PDO.Lower polarity can inhibit the aggregation of Raney copper but it's bad for the separation of 1,2-PDO from the catalyst surface,which lead to higher conversion and lower selectivity.The glycerol conversion was 79.1%and the selectivity of 1,2-PDO was 89.3%at the condition of4.0 MPa,215oC,30%glycerol ethanol solution in batch reactor.Although Raney Cu is easy to prepare,the poor mechanical strength and easy to pulverization.The supported Raney Cu/Al₂O₃ was prepared by forming,calcination and alkali activation.The highest conversion is99.0%and selectivity of 1,2-PDO is 73.6%at 215oC,3MPa,LHSV=1h^-1,H₂/Gly=500:1,20%glcerol solution.Meanwhile,Raney Cu/Al₂O₃ was modified to increase the catalytic activity at mild condition.Modification of Raney Cu/Al₂O₃ catalysts by ZnO and Cr₂O₃ by wet-mixed and alkali impregnation.Finally,the deactivation causes and regeneration conditions of Raney Cu/Al₂O₃ were studied.It was found that the Raney Cu was gradually transformed into crystalline Cu.The regeneration temperature and time were studied by calcination in air atmosphere.The results show that calcination at 650oC for 4 hours can recover the glycerol conversion to 98.9%,the selectivity of 1,2-PDO to 89.3%at 215oC,3MPa,LHSV=1h^-1,H₂/Gly=500,20%glcerol solution.The activity of regenerated catalysts is not stable because of the Raney Cu on the surface were oxidized to CuO in air.The original Raney Cu structure disappeared lead to low stability of the catalyst.