Study On Catalytic Hydrogenolysis Of Glycerol To Propylene Glycol

1,2-propanediol (1,2-PDO) and1,3-propanediol (1,3-PDO) are two versatile chemicals. The synthesis of1,2-PDO and1,3-PDO from glycerol is an environment-friendly process. Research on the catalysts used in these processes is of academic and application value.Firstly, a series of catalysts were prepared and their catalytic performance for producing1,2-propanediol through hydrogenolysis of glycerol was investigated and the results showed that Cu/MgO has the best catalytic activity. Secondly, Cu/MgO catalyst was modified by either acid or alkali and the effects on the catalytic performance after the modification were studied. The addition of NH4H2PO4, H3BO3, La(NO3)3·6H2O, etc. improved the acidity with different degree. The experiment results showed that the increase of acid amount could enhance the selectivity of1,2-propanediol. However decrease in the acid intensity could reduce the conversion of glycerol and the yield of1,2-propanediol. The addition of LiOH, NaOH, KOH and so on promoted the transformation of glycerol and the formation of1,2-propanediol. Additionally the enhancement in the catalytic performance was also attributive to the high dispersion of active ingredient on the support surface and to the strong interactions between them. The result of modification with LiNO3, NaN03, KNO3, RbN03, CsNO3and so forth showed that moderate alkalinity could increase the conversion of glycerol and the yield of1,2-propanediol. Lastly, the catalytic performance of some silica-supported copper-heteropoly acid catalysts and the effect of solvent like1-propanol on the hydrogenation of glycerol to1,3-propanediol were studied. It was found that Cu-H4SiW12040/Si02exhibited the best catalytic performance and1-propanol solvent was beneficial for the formation of1,3-propanediol. Under the reaction conditions of weight ratio of Cu-H4SiW12040/Si02/glycerol=11:100,1-propanol as solvent,50%glycerol solution, reaction temprature of180℃, reaction time of16h, H2initial pressure of9.0MPa and stirring rate of600r/min, the conversion of glycerol was28.3%, the yield and selectivity of1,3-propanediol reached6.32%and22.3%, respectively. Within the reaction time of32h, the conversion of glycerol, the selectivity and yield of1,3-propanediolin kept roughly stable. Furthermore, poor catalyst stability was probably caused by the growth of Cu0particle grain size, the loss of copper species and silicotungstic acid. Furthermore GC-MS was used for analysis of the by-products and possible side-reactions.