Studies On Synthesis Of Ethylene Glycol Monoethyl Ether Acetate By Transesterification On Solid Bases

Due to very strong solubility for polymers,ethylene glycol monoether acetate as a new all-purpose solvent is used in very broaden applying fields.The main problems in the present industry production for ethylene glycol monoether acetate by transesterification are as follows:most of the catalysts being used are expensive and toxicity and they also can not be recycled.In this paper,we firstly use heterogeneous basic catalysts in the transesterification reaction for the synthesis of ethylene glycol monoether acetate.Three kinds of inorganic solid bases such as hydrotalcite-like solid base,oxide solid base and supported solid base have been studied in this paper for the catalytic synthesis of ethylene glycol monoether ether acetate(EEA) by transesterification.The synthesis of propylene glycol methyl ether acetate(PMA) as a member of P series which is less poisonous is also studied.1.Synthesis of EEA by transesterification on Mg-Al hydrotalcite-like solid baseMg-Al hydrotalcite-like solid bases with different molar ratios of Mg and Al were prepared using co-precipitation method.The results were shown below:(1) When n(Mg/Al)=3,the Mg-Al hydrotalcite-like solid base had a good catalytic effect in synthesis of EEA and the yield of EEA was 90.8%.(2) The Mg-Al hydrotalcite-like solid base with n(Mg/Al)=3 was characterized by many apparatus.These results showed that the material had a typical structure of hydrotalcite-like compound brucite-layer and also had a stability catalytic effect.2.Synthesis of EEA by Transesterification on Oxide Solid Base such as MgO and CaO(1) The activity of MgO was mainly from OH which was due to its surface adsorption of H₂O,but the activity of CaO mainly resulted from O^2- in it.(2) By using the solid base CaO(800℃,5 h) as a best selected catalyst,the optimal reaction conditions and excellent results are given as follows:molar ratio of ester and EE was 4:1,the amount of catalyst(based on the whole amount of the reactant) was 1.0 wt%,reaction temperature was 80 to 100℃, reacted 5 h under common pressure,the yield of EEA was 99.0%.(3) It was very convenient to recycle the solid base CaO(800℃,5 h).It could be recovered after 5 times reuse without significant loss of its catalytic activity.3.Synthesis of EEA by Transesterification on Supported Solid BaseThe supported solid bases were prepared by an incipient wetness impregnation method.Using KF,K₂CO₃ and KOH as active substance respectively,different carriers and different loading were studied.The results are as follows:(1)The best supported catalyst was 10%K₂CO₃/Al₂O₃.(2)By comparing,we found that the best catalyst was 10%K₂CO₃/Al₂O₃.(3)By comparison of traditional homogeneous catalysts,it proved that 10% K₂CO₃/Al₂O₃ has a better activity and it is inexpensive and reusable.(4) 10%K₂CO₃/Al₂O₃ was always used for different ethylene glycol ether as reactants.The results were always excellent and the yields of aimed products were more than 95%.(5) The reaction mechanism was discussed in order to give something valuable for further research.4.Synthesis of PMA(1) By using the solid base 10%K₂CO₃/Al₂O₃ as catalyst,the optimal reaction conditions and excellent results are given as follows:molar ratio of ester and PM was 6:1,the amount of catalyst(based on the whole amount of the reactant) was 1.0 wt%,reaction temperature was 80 to 100℃,reacted 5 h under common pressure,the yield of EEA was 95.9%.(2) It is also very convenient to recycle the solid base 10%K₂CO₃ Al₂O₃.It could be recovered after 5 times reuse without significant loss of its catalytic activity. (3)By comparison of traditional homogeneous catalysts,it proved that 10% K₂CO₃/Al₂O₃ is an excellent heterogenous catalyst in synthesis of PMA.