氨基甲酸酯型有机催化剂的制备及应用

Preparation and application of carbamate organocatalyst

摘要:

利用碳酸乙烯酯（EC）和四乙烯五胺（TEPA）原料，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）；以FTIR、NMR对其结构进行了表征，分析了催化机理；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按摩尔比5∶1在140 ℃反应2 h制得的TEPA-EC催化剂具有较高的催化活性。对于DMC与EtOH按照摩尔比2∶1在78 ℃反应7 h的酯交换反应：TEPA-EC用量为原料总质量1%时，EtOH转化率（X）为59.50%、EMC选择性（S）为83.77%，催化效率与工业化应用的乙醇钠相当；3%用量的TEPA-EC在8次重复使用和14次带水循环使用过程中，X与S分别在62.35%、86.03%和57.33%、87.91%附近波动，表现出远优于乙醇钠的稳定性和耐水性。

Abstract:

A carbamate organocatalyst (TEPA-EC) for the synthesis of methyl ethyl carbonate (EMC) was synthesized by the addition reaction between tetraethylenepentamine (TEPA) and ethylene carbonate (EC). The structure of TEPA-EC was characterized by FTIR and NMR, and the catalytic mechanism was analyzed. The effects of synthesis and application conditions of TEPA-EC were investigated on its catalytic activity and transesterification efficiency, respectively. The stability and water resistance of TEPA-EC were also assessed. The results shows that the hydroxyethyl tert-aminoformate group of TEPA-EC can facilitate the transesterification between dimethyl carbonate (DMC) and ethyl alcohol (EtOH) via synergistic hydrogen-bonding. The TEPA-EC catalyst of high catalytic activity can be obtained when EC reacts with TEPA at 140℃ for 2 hours by a molar ratio of 5∶1. When DMC reacts with EtOH by a molar ratio of 2∶1 at 78℃ for 7 hours and the amount of TEPA-EC accounts for 1% of the total mass of raw materials, the conversion of EtOH and selectivity of EMC are 59.50% and 83.77% respectively. The catalytic efficiency of TEPA-EC is comparable to that of sodium ethoxide used in industrial applications. For the transesterification under the same conditions as above, the conversion of EtOH and selectivity of EMC fluctuate around 62.35%, 86.03% and 57.33%, 87.91% respectively during 8 times of repeated use and 14 times of circulated use with water, when the amount of TEPA-EC catalyst is 3% of the total mass of raw material. TEPA-EC shows much better stability and water resistance than sodium ethoxide.