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高岭石甲烷吸附规律的分子模拟研究
唐巨鹏,孙胜杰,包思远
0
(辽宁工程技术大学力学与工程学院,辽宁阜新123000)
摘要:
高岭石作为黏土矿物的主要吸附载体,其对甲烷吸附的贡献不可忽略。考虑高岭石独特的1∶1型双层晶体结 构,建立高岭石双层吸附空间模型。采用巨正则系综下的蒙特卡洛方法研究甲烷分子与高岭石超晶胞的定位吸附 模拟和高岭石对甲烷的等温吸附模拟,分析高岭石的晶体结构、温度和含水率对甲烷吸附行为的影响。研究结果 表明:高岭石硅氧四面体层(硅氧烷化面)对甲烷的吸附作用强于铝氧八面体层(铝氧羟基化面),甲烷优先吸附于 硅氧烷化面;吸附的甲烷分子呈聚集态分布于硅氧四面体六元环空穴上方位置,且以正三角锥构型吸附最为稳定; 在280~400 K温度下,高岭石吸附甲烷符合Langmuir等温吸附类型,且属于物理吸附;甲烷吸附量和吸附热均随温 度升高而呈线性降低,证实可以利用低温条件下的吸附量预测高温条件下的吸附量;高岭石吸水饱和前,水分子的 存在不会改变高岭石对甲烷的吸附趋势和类型,仅降低甲烷吸附量,当含水率由0增至20.94%,甲烷吸附量下降 35.06%。
关键词:  分子模拟  蒙特卡洛方法  高岭石晶体结构  页岩气吸附  吸附量
DOI:10.13673/j.cnki.cn37-1359/te.2019.04.006
基金项目:国家自然科学基金项目“煤系页岩瓦斯吸附解吸渗流与变形耦合作用多尺度联动机制研究”(51374119)。
Molecular simulation of methane adsorption on kaolinite
TANG Jupeng,SUN Shengjie,BAO Siyuan
(School of Mechanics and Engineering,Liaoning Technical University,Fuxin City,Liaoning Province,123000,China)
Abstract:
Kaolinite,as the main adsorbent carrier of clay minerals,cannot be ignored for its contribution to methane adsorption. The double-layer adsorption space model of kaolinite was established in the consideration of the unique 1∶1 double-layer crystal structure of kaolinite. Using the Grand Canonical Monte Carlo method,localized adsorption simulation of single methane molecule in kaolinite supercell and adsorption isothem simulation of methane in kaolinite were carried out to analyze the effects of kaolinite crystal structure,temperature,and moisture content on the adsorption behavior. The results show that the adsorption of methane on kaolinite silico tetrahedron(silicoxylated surface)is stronger than that of Al oxygen eight surface layer(aluminum oxygen hydroxylated surface). Methane adsorbs on the alkoxylation surface with priority.The adsorbed methane is clustered in the position above the six membered ring hole of silicon tetrahedron and the adsorption with the triangular pyramid configuration is the most stable. The adsorption of methane on kaolinite at 280-400 K is consistent with Langmuir isothermal adsorption type and belongs to physical adsorption. The adsorption capacity and adsorption heat of methane decrease linearly with the increase of temperature. It is confirmed that the adsorption capacity at high temperature can be predicted according to low temperature. Before kaolinite is saturated with water,the presence of water does not change the adsorption trend and the type of methane adsorption,and it only reduce the amount of methane adsorption. When the water content increases from 0 to 20.94%,the adsorption capacity of methane is reduced by 35.06%.
Key words:  molecular simulation  Monte Carlo method  kaolinite crystal structure  shale gas adsorption  adsorption capacity

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