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基于量子化学计算的尿素醇解制备碳酸乙烯酯反应机理研究

发表时间:2015-02-15  浏览量:1873  下载量:815
全部作者: 杨伯伦,程进,康程,张应
作者单位: 西安交通大学化学工程与技术学院
摘 要: 采用密度泛函理论(density functional theory,DFT)对尿素(Urea)与乙二醇(EG)反应制备碳酸乙烯酯(EC)的微观机理进行了研究。在B3LYP/6-31G(d,p)水平上优化了反应体系中所有反应物、中间体、过渡态和产物的几何构型,通过振动频率分析和内禀反应坐标(internal reaction coordinate,IRC)跟踪验证了过渡态分析的正确性。计算结果表明:每一步反应均有H原子的转移,EG羟基与反应物形成的氢键对反应有促进作用;反应有直接醇解-消去和分解-加成-消去2条路径,其中后者的势垒低,为主反应路径;主反应路径中最后一步羟乙基氨基甲酸酯(HEC)消去氨气生成EC反应的势垒最高,为整个反应的控制步骤。
关 键 词: 化学工程基础学科;反应机理;密度泛函理论;尿素;碳酸乙烯酯
Title: Mechanism of synthesis of ethylene carbonate from urea and ethylene glycol: quantum chemistry computing
Author: YANG Bolun, CHENG Jin, KANG Cheng, ZHANG Ying
Organization: State Key Laboratory of Multiphase Flow in Power Engineering, School of Chemical Engineering and Technology, Xi'an Jiaotong University
Abstract: The mechanism for the synthesis of ethylene carbonate (EC) from urea and ethylene glycol (EG) has been studied based on the density functional theory (DFT). At the B3LYP/6-31G (d, p) level, the geometries of all species in the reaction system (reactants, isomers, transition states and products) were optimized. The transition states were validated by the vibrational frequency analysis and the calculations of the internal reaction coordinate (IRC). The computational results were as follows: firstly, transfer of H atoms was in every step of the reaction, and H-bond with hydroxyl of EG promoted the reaction; secondly, the reaction had two possible paths, direct-alcoholysis-elimination and decomposition-addition-elimination, and the main reaction pathway was the latter because of it’s low energy barrier. Finally, elimination reaction of 2-hydroxyethyl carbamate (HEC) to EC was the control step of entire reaction due to its highest energy barrier.
Key words: basic subject of chemical engineering; reaction mechanism; density functional theory; urea; ethylene carbonate
发表期数: 2015年2月第3期
引用格式: 杨伯伦,程进,康程,等. 基于量子化学计算的尿素醇解制备碳酸乙烯酯反应机理研究 [J]. 中国科技论文在线精品论文,2015,8(3):296-304.
 
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