温和条件下甲烷提高水合物储氢稳定特性机理  

Mechanism of methane in improving the stability of hydrate hydrogen storage under mild conditions

作　　者：王芳[1,2] 穆金池 张政[1] 黄泽皑 郭利红 周莹[1,2] WANG Fang;MU Jinchi;ZHANG Zheng;HUANG Zeai;GUO Lihong;ZHOU Ying(School of New Energy and Materials,Southwest Petroleum University,Chengdu,Sichuan 610500,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation//Southwest Petroleum University,Chengdu,Sichuan 610500,China;Sichuan Golden-Elephant Sincerity Chemical Co.,Ltd.,Meishan,Sichuan 620031,China)

机构地区：[1]西南石油大学新能源与材料学院 [2]油气藏地质及开发工程全国重点实验室·西南石油大学 [3]四川金象赛瑞化工股份有限公司

出　　处：《天然气工业》2024年第2期188-196,共9页Natural Gas Industry

基　　金：国家自然科学基金项目“定向调控甲烷活化生成抗积碳中间体提升Ni/Ce O_(2)光热催化甲烷干重整性能研究”(编号:22209136);四川省自然科学基金项目“油水乳液/低维纳米流体水合物促进剂用于甲烷制合成氨脱碳关键技术”(编号:2023NSFSC0108);四川省重点研发项目“功能化碳纳米管阵列快速捕获分离CO_(2)关键技术”(编号:2022YFSY0050)。

摘　　要：CH_(4)作为促进剂可大幅降低水合物储氢苛刻的热力学条件并提高H_(2)水合物的总储能密度,但目前对CH_(4)提升水合物储氢机理的认识较为缺乏。为此,通过分子动力学模拟研究并建立了CH_(4)/H_(2)双客体分子水合物模型,采用径向分布函数、构象分析和均方位移等方法综合分析了不同温度和压力下水合物结构的稳定性,探究了H_(2)占据孔穴位置、占据比例和水合物热力学稳定性之间的关联,揭示了温和条件下CH_(4)促进水合物储氢的微观机理。研究结果表明:(1)纯H_(2)水合物在严苛条件下笼型结构破损严重,而纯CH_(4)水合物在263~273 K及5~20 MPa温压条件下能稳定存在,说明CH_(4)水合物具备良好的热力学稳定性;(2) 263 K下储氢结构更为稳定,而5^(12)小笼可填充1~2个H_(2)分子,5^(12)6~2大笼中最佳储存3个H_(2)分子,且大笼储氢结构对水合物稳定性影响大,受温度的影响更为敏感。结论认为,CH_(4)/H_(2)水合物储氢体系3L+2S、3L+2L、2S+2S体系在263 K、15~20 MPa温和条件下综合性能较好,其中3L+2S具备最优的热力学稳定性,储氢密度可达0.301%(质量百分比),该研究成果可为水合物储氢技术开发提供理论指导和技术参考。Methane as an accelerator can significantly reduce the harsh thermodynamic conditions of hydrogen storage in hydrates and increase the total energy storage density of hydrogen hydrate.At present,however,the mechanisms of methane in improving hydrate hydrogen storage have not been understood.In this paper,the CH_4/H_(2) double-guest molecular hydrate model is established by virtue of molecular dynamics simulation.Then,the stability of hydrate structure at different temperatures and pressures is comprehensively analyzed by means of radial distribution function,conformation analysis and mean square displacement.Finally,the relationships between the position and proportion of H_(2) occupied holes and the thermodynamic stability of hydrate are explored,and the microscopic mechanism of methane promoting hydrogen storage in hydrate under mild conditions is revealed.And the following research results are obtained.First,the cage structure of pure hydrogen hydrate is seriously damaged under harsh conditions,while pure methane hydrate can remain stable at 263-273 K and 5-20 MPa,indicating that methane hydrate has good thermodynamic stability.Second,the hydrogen storage structure is more stable at 263 K,while the 5^(12) small cage can be filled with 1 to 2 H_(2) molecules,and the 5^(12)6^(2) large cage can optimally store 3 H_(2) molecules.The hydrogen storage structure of the large cage has a great influence on the stability of the hydrate and is more sensitive to temperature.In conclusion,the CH_4/H_(2) hydrate hydrogen storage systems 3L+2S,3L+2L and 2S+2S perform better under the mild conditions of 263 K and 15-20 MPa.And among them,the system 3L+2S is the best in thermodynamic stability with the hydrogen storage density of 0.301%(mass fraction).The research results can provide theoretical guidance and technological reference for the development of hydrate hydrogen storage technology.

关 键 词：氢气水合物 甲烷 储氢技术 储氢密度 分子动力学 储氢机理 稳定性 

分 类 号：TK91[动力工程及工程热物理]