Abstract: N-methylacetamide(NMA) was used as entrainer in separating acetic acid from water with extractive distillation, and the interaction mechanism in this process was studied by using the density functional theory.The optimization geometries and vibration frequencies of NMA-acetic acid and NMA-water complexes were calculated at the B3LYP/6-311G(d,p) level.After the basis set superposition error (BSSE) correction and the zero point vibration energy (ZPE) correction, the interaction energies for three types of NMA-acetic acid complexes and one type of NMA-water complex were -44.3,-35.5,-32.4 and -16.0 kJ·mol-1 respectively, which showed that NMA had a great affinity for acetic acid than water.The boiling point of the NMA-acetic acid complex was higher than that of acetic acid so that acetic acid is easily preserved in the liquid phase, which is in agreement with the VLE experiment for NMA+acetic acid+water system that gave a relative volatility of 3.0—4.0.The results of natural bond orbital (NBO) population analysis revealed that there was charge-transfer in the complex formation, and acetic acid acted as electron acceptor during this transformation.

摘要： 以N-甲基乙酰胺（NMA）作溶剂，用理论计算方法对萃取精馏醋酸脱水过程的作用机理进行研究。NMA与水\醋酸之间都有氢键形成，经计算得到NMA-醋酸复合物的稳定化能在-32.4~-44.3kJ/mol之间，且平面构型的NMA-醋酸复合物稳定能较高，而NMA与单分子水的稳定化能仅为-16.0kJ/mol。这说明NMA对醋酸具有选择性结合能力，使得醋酸不易挥发到汽相中去；这与VLE实验结果相一致，加入NMA可将水对醋酸的相对挥发度提高至3.0~4.0。用自然键轨道(NBO)分析表明，以上两种复合物形成过程中均伴随着电荷转移现象，整体上醋酸分子作为电荷受体而存在。