煤表面分子对甲烷吸附力场研究

西安科技大学 理学院,陕西 西安 710054

密度泛函; 吸附模型; 平衡结构; 密立根电荷

Study on the adsorption force field of methane on coal surface molecules
YANG Hua-ping,LI Ming

(College of Sciences,Xi'an University of Science and Technology,Xi'an 710054,China)

density function theory; absorption model; equilibrium structure; mulliken charges

DOI: 10.13800/j.cnki.xakjdxxb.2015.0116

备注

采用密度泛函理论DFT方法,建立煤大分子骨架模型,并以范德华力作用半径为边界条件,构建煤大分子对CH4分子吸附的量子动力学模型,在6-311G++基组上对煤大分子骨架模型和吸附模型结构进行优化,通过密立根电荷量分析了煤大分子表面的吸附空位,以及甲烷气体分子从游离态到吸附态的物理结构和特性变化。研究结果表明,煤表面分子和甲烷分子之间的吸附力场主要是静电场,甲烷分子在吸附过程中被极化,产生电偶极矩,C-H分子键长增大,吸附质和吸附剂之间的范德华力主要是诱导力和色散力以及甲烷分子被极化后的取向力,煤大分子表面的吸附空位可以通过煤大分子中各原子的密立根电荷量分析定量确定,通过模型结构优化发现,同一吸附空位可以对应多种甲烷分子吸附平衡结构,煤对甲烷分子的吸附为多分子层吸附。

The coal molecule model and the absorption model of coal and methane were established and optimized according to Van der Walls force with density function theory of 6-311G++ sets,the physical structure and molecular electric changes of methane molecules were analyzed from the free state to the absorption state,the adsorption site on the surface of coal can be determined by the mulliken charges of the coal molecule.The results show that the force field between the adsorbed methane molecular and coal surface molecules is mainly electrostatic field,the methane molecules are polarized with the electric dipole moment in the adsorption process,and its bond length increases.The adsorption force between the adsorbate and adsorbent is mainly induced forces,dispersion forces and orientation force,the adsorption site on the surface of coal may be quantitatively checked by the mulliken charges analysis.The optimization results also reveal the same adsorption site can correspond to multiple adsorption equilibrium structure of methane,which means the absorption between the coal and methane is multilayer adsorption.