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本文采用密度泛函理论在B3LYP/6-311++G(d,p)水平上分析了N-甲基吡咯烷酮(NMP)作为萃取剂萃取精馏分离醋酸-水体系的微观机理。优化出NMP-水和NMP-醋酸的稳定构型,分析了稳定构型的相互作用能、振动频率和自然键轨道。与NMP-水相比,NMP-醋酸之间形成的氢键更稳定,且NMP-醋酸之间的相互作用能更大。自然键轨道分析结果进一步证明NMP和醋酸之间形成了更为稳定的络合物,且醋酸为电子受体,NMP为电子供体。NMP与醋酸形成稳定的氢键络合物,显著提高了水/醋酸的相对挥发度,使二者的分离更容易。采用相同的方法计算出了N-甲基乙酰胺(NMA)作为萃取剂在醋酸-水体系中的作用机理,并比较了NMP和NMA的萃取效果,结果显示萃取效果NMP>NMA,与文献报道实验结果一致,为工业应用提供了参考。
In this paper, the density functional theory (DFT) was used to analyze the micro-mechanism of extraction and separation of acetic acid-water system with N-methylpyrrolidone (NMP) as extractant at B3LYP / 6-311 ++ G (d, p) The stable configuration of NMP-water and NMP-acetic acid was optimized, and the interaction energies, vibrational frequencies and natural bond orbital of the stable configuration were analyzed. Compared with NMP-water, hydrogen bonds formed between NMP-acetic acid are more stable, and the interaction between NMP-acetic acid can be greater. Natural bond orbital analysis further demonstrated that a more stable complex was formed between NMP and acetate with acetate as the electron acceptor and NMP as the electron donor. NMP and acetic acid to form a stable hydrogen bond complex, significantly increased water / acetic acid relative volatility, so that the separation of the two easier. The same method was used to calculate the mechanism of N-methylacetamide (NMA) as extractant in acetic acid-water system. The extraction results of NMP and NMA were compared. The results showed that NMP> NMA was reported in the literature The experimental results are consistent, providing a reference for industrial applications.