Study On Oxidative Carbonylation Of Biomass-based Glycerol To Glycerol Carbonate Over Pd/CeO₂ Catalyst

With the development of the biodiesel industry,there is a large amount of glycerol produced as a byproduct.To maintain the balance of the glycerol in existing market,how to convert glycerol into high value-added products and achieve efficient use of resources have become the focus of research.Using glycerol and CO to synthesize high value-added glycerol carbonate is one of the important ways to reuse glycerol.Oxidative carbonylation of glycerol uses glycerol,CO and other simple and cheap chemicals to synthesize glycerol hydrocarbons,and water is the only theoretical byproduct.It is an atomic economical and environmentally friendly process.Firstly,CeO₂ nanotubes were prepared by hydrothermal method using CeCl₃·7H₂O as the cerium source,and the Pd/CeO₂-NTsJ catalysts were prepared by impregnation method.In the process,CeO₂ nanotubes were as the support for the oxidative carbonylation of glycerol.In the reaction,glycerol:Pd=1479?molar ratio?,CO 3.3 MPa,O₂ 1.7 MPa,140°C,1.7 h,the conversion of glycerol was 93.5%,and the selectivity of glycerol carbonate reached 99.9%.But it was severe for catalyst to be recycled after three times in inactivation,the conversion of glycerol was merely 61.5%.Secondly,in order to solve the inactivation of impregnation method,we prepared the Pd/CeO₂-NTsY catalyst was prepared by in-situ method and the reaction conditions was optimized.In the reaction,glycerol:Pd=1479?molar ratio?,CO 3.3 MPa,O₂ 1.7 MPa,140°C,2 h,the conversion of glycerol was 89.6%and the selectivity of glycerol carbonate was up to 99.9%.After 5 recycles of the catalyst,the conversion of glycerol was 75.8%.Via the characterization analysis,the main reason for inactivation of the catalyst was the loss of the active component Pd;in addition,the active component Pd has accumulated during the reaction system,which was another important reason for the inactivation of the catalyst.The Pd/CeO₂-NTsY catalyst prepared by the in-situ method can effectively reduce these problems and maintain high catalytic activity.Finally,PdCl₂ was immobilized in the ionic liquid to form PdCl₂ ionic liquid complex that increased the rate of electron transfer and catalyst circulation through the ionic liquid,thereby increased the catalytic activity of the catalyst.We find that[BMIM]BF₄ played a catalytic effect on the oxidative carbonylation of glycerol to some extent,but it did not reach the original intention of fixing PdCl₂,and the occurrence of side reactions was accompanied by the introduction of ionic liquids.Therefore,the further research on the application of ionic liquids in the oxidative carbonylation of glycerol is needed...