| As one of the ideal renewable resources, glycerol can be transformed to glyceryltriacetate by catalytic esterification, and to propanediols, acetol and ethylene glycol bycatalytic hydrogenolysis. Among them,1,2-propanediol and1,3-propanediol areconsidered as the more important products with high value. As a result, the catalyticesterification and hydrogenolysis reactions over a novel catalytic system withheteropoly ionic liquids have been studied in this paper. A series of heteropoly ionicliquids have been prepared and optimized in the esterification and hydrogenolysisreactions to give the suitable reaction conditions. As well, the reaction mechanism hasbeen also discussed.The catalytic activities of the heteropoly-organic hybrid ionic liquids withdifferent anions and cations, accordingly different acidities and other properties, havebeen investigated. The structures of optimized catalysts have been characterized byFT-IRã€TG and1H-NMR. The n-butyl amine potentiometric titration method has beenalso employed to study the effect of anions and cations structures on their acidities andcatalytic performances.The influence of molar ratio of acetic acid to glycerol, dosage of catalyst andreaction time on the catalytic performance have been studied to obtain more glyceryltriacetate. Under the conditions: molar ratio of acetic acid to glycerol6:1,0.026%(molar ratio to glycerol) H2[TEAPS]PW12O40catalyst dosage, reactiontemperature110oC and reaction time8h, the glycerol conversion and selectivity forglyceryl triacetate can reach as high as99%and98%respectively. Moreover,H2[TEAPS]PW12O40catalyst could be reused conveniently without evidentinactivation.In the research of catalytic hydrogenolysis of glycerol to prepare propanediolsover ionic liquids/Raney Ni systems, it has been found that the ionic liquids with acidity could improve the conversion of glycerol. Moreover, the coversions underLewis ionic liquids as well as heteropoly ionic liquid can exceed90%. On the otherhand, only heteropoly ionic liquid has shown a good separating property. Based on thedehydration-hydrogenation mechanism, the catalytic hydrogenolysis of propanediolsand intermediates have been studied to discuss the process of catalytic hydrogenolysisof glycerol. The results have shown that the low selectivity of1,3-propanediol is due toit’s instability under the reaction conditions in this study.Over the optimized composite catalyst [HMIM]3PW12O40/Raney Ni system, thereaction conditions of catalytic hydrogenolysis of glycerol to prepare1,2-propanediolhave been investigated.At the follow optimized conditions:20g40%glycerol solution,[HMIM]3PW12O400.2mmol, Raney Ni0.3g, hydrogen pressure6Mpa(hydrogenalcohol:2.37:1),230℃reaction temperature,11h, the conversion of glycerol and theselectivity for1,2-propanediol can reach83%and57%respectively. Besides, thecomposite catalyst can be recycled expediently with good performances. |
