基于吸附位理论的CO2/CH4在高岭石中竞争吸附的分子模拟  

Molecular Simulation of CO2/CH4 Competitive Adsorption in Kaolinite Based on Adsorption Potential Theory

作　　者：宋正平 张彬 康天合 SONG Zheng-ping,ZHANG Bin, KANG Tian-he(Institute of Mining Technology, Taiyuan University of Technology, Taiyuan 030024, China)

机构地区：[1]太原理工大学采煤工艺研究所

出　　处：《矿物岩石地球化学通报》2018年第4期724-730,共7页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(51174141,50974093)

摘　　要：为了阐明CH4与CO2在高岭石中的竞争吸附机理,采用蒙特卡洛方法构建了高岭石超胞模型,模拟计算了高岭石吸附CH4与CO2在不同温度及压力条件下的变化规律,分析了不同孔径对高岭石吸附CO2和CH4的影响。结果表明,不同温度下高岭石对CH4与CO2分子的吸附量均符合Langmuir模型,在相同压力条件下,高岭石对CO2分子的吸附量远远大于对CH4分子的吸附量;293.15 K时,高岭石对CO2的吸附具有明显的竞争优势,CH4在CO2分子的影响下不再符合Langmuir曲线,说明高岭石与CO2分子的相互作用强于与CH4之间的相互作用;随着孔径的增大,高岭石对CH4与CO2的吸附量均减小,表明CH4和CO2主要吸附在微孔中;高岭石吸附CH4与CO2分子后体系的总能量和非成键能发生了变化,说明高岭石与CO2的相互作用能要强于高岭石与CH4的相互作用能,高岭石对CH4的吸附为典型的物理吸附,而对CO2的吸附以物理吸附为主,且伴随着微弱的氢键作用。研究结果为阐明CO2和CH4在黏土矿物的赋存机理以及CO2驱替CH4的研究提供了一定的理论依据。In order to elucidate the competitive adsorption mechanism of CH4 and CO2 in kaolinite,we have constructed the kaolinite supercavity model by using Monte Carlo method,simulated and calculated effective variations of kaolinite adsorbing individual gas or mixed gas of CH4 and CO2 at various temperatures（ 283. 15 K,293. 15 K,313. 15 K） and pressures（ 1 MPa,2 MPa,…,9 MPa,10 MPa）,analyzed effects of various pore sizes（ 0. 72 nm,1. 44 nm,2. 88 nm） of kaolinite on the adsorption of CO2 and CH4,respectively. The results show that the capacity of kaolinite adsorbing CH4 and CO2 is consistent with that of the Langmuir curve at various temperatures. Under the same pressure conditions,the capacity of kaolinite adsorbing CO2 is much larger than that of kaolinite adsorbing CH4; The adsorption of CO2 by kaolinite has obviously competitive advantage comparing to the adsorption of CH4 in the mixed CO2/CH4 gas. The capacity of adsorbing CH4 is no longer accorded with that of the Langmuir curve under the influence of CO2. These indicate that The intensity of interaction between kaolinite and CO2 molecules is stronger than that of the interaction between kaolinite and CH4 molecules.With the increase of pore sizes of the kaolinite,the capacities of kaolinite adsorbing CH4 and CO2 are decreased,indicating that CH4 and CO2 are mainly adsorbed in micro-pores of kaolinite. The variations of the total system energy and nonbonding energy of the kaolinite caused by its adsorption of CH4 and CO2 molecules indicate that the interaction energy of kaolinite and CO2 is stronger than that of kaolinite and CH4. The adsorption of CH4 by kaolinite is a typical physical ad-sorption,while the adsorption of CO2 by kaolinite includes major physical adsorption and minor chemical adsorption of weak hydrogen bonding effect. Our research results have provided a certain theoretical basis for elucidating the adsorption mechanism of CO2 and CH4 molecules by kaolinite and for studying the mechanism of CH4 substituted by CO2 in clay minerals.

关 键 词：高岭石 吸附位 竞争吸附 分子模拟 

分 类 号：TE319[石油与天然气工程—油气田开发工程]