羟乙基乙二胺/甲基二乙醇胺混合醇胺溶液吸收CO_(2)的密度泛函研究  

Density functional theory investigation on carbon dioxide absorption process in aqueous solutions of methyl-di-ethanolamine and N-(2-aminoethyl)-ethanolamine

作　　者：姜蔚 刘艳升[2] 邵子奇 郝亚苹 芦泽宇 JIANG Wei;LIU Yan-sheng;SHAO Zi-qi;HAO Ya-ping;LU Ze-yu(PetroChina Fuel Oil Co.,Ltd Research Institute,Beijing 100195,China;College of Chemical Engineering and Environment,China University of Petroleum,Beijing 102249,China)

机构地区：[1]中石油燃料油有限责任公司研究院,北京100195 [2]中国石油大学(北京)化学工程与环境学院,北京102249

出　　处：《分子科学学报》2022年第5期407-414,共8页Journal of Molecular Science

基　　金：国家自然科学基金资助项目(21576287)。

摘　　要：根据两性离子机理对羟乙基乙二胺(AEEA)和甲基二乙醇胺(MDEA)的混合醇胺水溶液吸收CO_(2)的反应步骤进行了理论研究,在B3LYP/6-311++G(d,p)计算水平下,对各个反应的过渡态构型进行了优化,并确定了反应路径及反应能垒.根据反应能垒确定了吸收CO_(2)过程中的主要反应,并基于过渡态理论对主要反应的反应速率常数进行了计算,反应速率常数针对隧道效应进行了校正.研究结果表明,在吸收过程中,CO_(2)更易于与AEEA中的伯胺N原子发生反应生成两性离子,然后再与溶液中含有碱性基团的物质发生分子间氢转移.其中,两性离子的形成过程为吸收过程的速控步骤,在298 K下的反应速率常数为4.59×10^(4) L·mol^(-1)·s^(-1),随着温度上升,反应速率常数显著增加.氢转移的反应速率常数显著高于前者,3种碱性基团在氢转移过程中起到的作用比较相似,298 K下的反应速率常数也很接近.AEEA和MDEA会催化CO_(2)与水反应并生成碳酸氢根,但逆反应能垒低,反应产物不稳定,容易分解.According to the‘zwitterion mechanism’,carbon dioxide absorption process in aqueous solutions of methyl-di-ethanolamine(AEEA)and N-(2-aminoethyl)-ethanolamine(MDEA)is studied in this work.The transition state and intermediate structures were optimized at the B3 LYP/6-311++G(d,p)level.Use intrinsic reaction coordinate theory to calculate reaction paths and reaction energy barriers.To make the result more accurate,zero point energy correction is used to revise the energy of molecular structures.Each transition state is confirmed by the frequency calculation,and there is only one virtual frequency and the vibration direction connects the reactant to the product.The main reactions in the absorption process were determined according to the energy barrier of each reaction,and the reaction rate constants of main reactions were calculated based on the transition state theory.Between 298 K and 318 K,tunneling effect has great influence on the reaction constant,thus the correction term of transmission coefficient was added.The results show that during the absorption process,COis more likely to react with primary amine of AEEA to generate‘zwitterion’,then intermolecular hydrogen transfer occurs between the‘zwitterion’and the basic substance in the solution.The formation path of the‘zwitterion’is the rate-controlling step in the absorption process,and the reaction rate constant is 4.59×10^(4)L·mol^(-1)·s^(-1)at 298 K and it increases significantly with the rise of temperature.There are three kinds of basic groups in the aqueous solution:the primary amine of AEEA,the secondary amine of AEEA and the tertiary amine of MDEA.These groups play similar roles in the process of hydrogen transfer,thereby the reaction rate constant are also similar(1.52×10,3.05×10^(9)and 2.36×10^(9)L·mol^(-1)·s^(-1)).The calculated results are in good coincidence with the experimental results.In this work,the possibility of intramolecular hydrogen transfer is also discussed,the results show that the energy barrier of this proces

关 键 词：醇胺 吸收 密度泛函理论 过渡态理论 反应速率常数 

分 类 号：O604[理学—化学]