CO_(2)置换CH_(4)水合物技术中主、客体分子间作用的DFT研究  

A DFT study of the interaction between host and guest molecules in the replacement of CH_(4) in natural gas hydrate by CO_(2)

作　　者：陈浩 颜克凤[2,3,4,5] 李小森 陈朝阳[1,2,3,4,5] 张郁 徐纯刚[1,2,3,4,5] CHEN Hao;YAN KeFeng;LI XiaoSen;CHEN ZhaoYang;ZHANG Yu;XU ChunGang(Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences,Guangzhou 510640;Key Laboratory of Gas Hydrate,Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences,Guangzhou 510640;Guangzhou Center for Gas Hydrate Research,Chinese Academy of Sciences,Guangzhou 510640;Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development,Guangzhou 510640;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院广州能源研究所,广州510640 [2]中国科学院广州能源研究所中国科学院天然气水合物重点实验室,广州510640 [3]中国科学院广州天然气水合物研究中心,广州510640 [4]广东省新能源和可再生能源研究开发与应用重点实验室,广州510640 [5]中国科学院大学,北京100049

出　　处：《北京化工大学学报（自然科学版）》2021年第2期31-40,共10页Journal of Beijing University of Chemical Technology(Natural Science Edition)

基　　金：国家自然科学基金重点项目(51736009);广东省促进经济发展专项资金(海洋经济发展用途)(粤自然资合[2018]002号/粤自然资合[2020]044号)。

摘　　要：天然气水合物是新型清洁能源,围绕CO_(2)置换CH_(4)水合物技术的研究对天然气水合物的资源开采和减少全球碳排放具有重要意义。其中,置换机理的解析是CO_(2)置换CH_(4)水合物技术的关键问题,对提升置换效率具有重要作用。为深入阐述置换机理的本质,采用量子力学(QM)方法对水合物中主、客体双分子聚体间的相互作用进行模拟。利用不同的密度泛函理论(DFT)方法对双分子聚体的结构及单点能进行计算分析,在对CO_(2)置换CH_(4)水合物过程的研究中,获得QM方法下进行几何结构优化和单点能计算的较优的计算参数。采用对称性匹配微扰理论(SAPT)进行能量分析,解析主、客体相互作用中各分子的贡献,并通过计算波函数信息分析约化密度梯度函数(RDG)、独立梯度模型(IGM)和静电势,定向研究主、客体分子间最主要的相互作用。研究结果表明CO_(2)置换CH_(4)水合物过程中主、客体分子间的作用主要由静电作用贡献,色散和诱导作用占比较小;在置换过程中,客体分子由CH_(4)转变为CO_(2)时色散作用影响减弱,静电作用影响加强。因此,静电作用是置换过程的关键,提高与H2O的静电作用是提升置换效率的有效方法。所得结果为CO_(2)置换CH_(4)水合物技术的发展提供了理论指导。Natural gas hydrate is a new type of clean energy. Studies of the replacement of CH_(4) in natural gas hydrate by CO_(2) have profound significance for both the exploitation of natural gas hydrate resources and the reduction of global carbon emissions. The micro-mechanism is a key issue in the replacement technology, and plays an important role in maximizing replacement efficiency. In this work, quantum mechanics(QM) methods have been used to simulate the interaction between host and guest dimers in hydrates to elaborate the replacement mechanism. By comparing the geometry and single point energy results calculated using different density functional theories(DFT), the optimal structure and calculated energy parameters for the process of the replacement of CH_(4) by CO_(2) were obtained. Decomposition energies were calculated by symmetry adapted perturbation theory(SAPT) in order to analyze the contribution of each molecule to the interaction between host and guest species in the hydrate. The reduced density gradient function(RDG), independent gradient model(IGM), and electrostatic potential results were obtained by analysis of wavefunction information in order to probe the key interactions between host and guest. The results showed that the interaction between the host and guest molecules during the replacement of CH_(4) by CO_(2) is mainly provided by electrostatic interaction, with only minor contributions from dispersion and induction effects. In the replacement process, the influence of dispersion effects was reduced when the guest molecule was changed from CH_(4) to CO_(2), and the electrostatic interaction was enhanced. The results indicated that electrostatic interaction is the major factor controlling the replacement of CH_(4) by CO_(2), and the increased electrostatic interaction between CO_(2) and H2O enhances the replacement efficiency. This study can provide theoretical guidance for the development of the necessary technology for the replacement of CH_(4) in natural gas hydrates by CO_(2).

关 键 词：天然气水合物 CO_(2)置换CH_(4)水合物过程 量子力学 对称性匹配微扰理论(SAPT) 密度泛函理论(DFT) 

分 类 号：TE31[石油与天然气工程—油气田开发工程]