氨基甲酸酯型有机催化剂的制备及应用

Preparation and application of carbamate organocatalyst

碳酸乙烯酯(EC)和四乙烯五胺(TEPA)通过加成反应制备了用于酯交换合成碳酸甲乙酯(EMC)的氨基甲酸酯型有机催化剂(TEPA-EC)。采用FTIR、NMR对其结构进行了表征,分析了其催化机理,考察了合成和使用条件对催化效率的影响,对TEPA-EC的稳定性和耐水性进行了测试。结果表明,TEPA-EC中的叔胺基甲酸羟乙酯基团通过协同氢键催化酯交换反应;EC与TEPA按物质的量比5∶1在140℃反应2 h制得的TEPA-EC具有较高的催化活性。对于n(DMC)∶n(EtOH)=2∶1在78℃反应7 h的酯交换反应,当EtOH 4.60 g、TEPA-EC用量为1%时(以原料总质量计,下同),EtOH的转化率为59.50%、EMC的选择性为83.77%,催化效率与工业化应用的乙醇钠相当;用量3%的TEPA-EC在8次重复使用和14次带水循环使用过程中,EtOH的转化率、EMC的选择性分别在62.35%、86.03%和57.33%、87.91%左右,优于乙醇钠的稳定性和耐水性。

A carbamate organocatalyst(TEPA-EC)for the synthesis of methyl ethyl carbonate(EMC)was synthesized from addition reaction of tetraethylenepentamine(TEPA)and ethylene carbonate(EC),then characterized by FTIR and NMR,and further analyzed for its catalytic mechanism.The influence of synthesis and application conditions on the catalytic activity and transesterification efficiency of TEPA-EC were investigated,followed by assessment on its stability and water resistance.The results showed that the hydroxyethyl tert-aminoformate group in TEPA-EC could facilitate the transesterification between dimethyl carbonate(DMC)and ethyl alcohol(EtOH)via synergistic hydrogen bonds.The TEPA-EC with high catalytic activity could be obtained under reaction conditions of n(EC)∶n(TEPA)=5∶1,temperature 140℃and reaction time 2 h.The conversion of EtOH and selectivity of EMC reached 59.50%and 83.77%,respectively,when DMC reacted with EtOH(4.60 g)by a molar ratio of 2∶1 at 78℃for 7 h with 1%(based on the total mass of raw materials,the same below)TEPA-EC.The TEPA-EC displayed comparable catalytic efficiency to that of sodium ethoxide used in industrial application.When 3%TEPA-EC was recycled 8 times alone and 14 times with water,the conversion of EtOH and the selectivity of EMC fluctuated around 62.35%,86.03%and 57.33%,87.91%,respectively,demonstrating much better stability and water resistance than sodium ethoxide.