H2O和CH4在煤表面竞争吸附机理

(1.中国矿业大学 煤矿瓦斯与火灾防治教育部重点实验室,江苏 徐州 221116; 2.中国矿业大学 安全工程学院,江苏 徐州 221116)

密度泛函理论; 竞争吸附; 吸附位; 吸附能

Competitive adsorption mechanism of H2O andCH4on coal surface
LIN Bai-quan1,2,LI Yong1,2,YANG Kai1,2,KONG Jia1,2,ZHANG Xiang-liang1,2

(1.Key Laboratory of Coal Methane and Fire Control,Ministry of Education,China University of Mining and Technology,Xuzhou 221116,China; 2.School of Safety Engineering,China University of Mining and Technology,Xuzhou 221116,China)

density functional theory; competitive adsorption; adsorption site; adsorption energy

DOI: 10.13800/j.cnki.xakjdxxb.2018.0602

备注

为从微观上探讨H2O和CH4在煤表面竞争吸附的机理,构建C30H14(9个苯环)代表煤局部表面,通过密度泛函理论分析甲烷分子,水分子和煤局部表面之间的相互作用。结果 表明,水分子在煤表面的吸附比甲烷分子在煤表面的吸附更加稳定,二者以最稳定吸附构型吸附时的吸附能分别为-13.23 kJ/mol和-10.13 kJ/mol.当甲烷分子与已吸附水分子的煤表面作用时,甲烷分子吸附能显著下降,吸附平衡距离增大,表明水分子能迫使甲烷吸附到不稳定位置。水分子和甲烷共存时,水分子处于吸附状态,甲烷分子处于脱附状态且总能量最低,进而从分子水平表明水和甲烷竞争吸附时水处于主导地位。

In order to study the mechanism of competitive adsorption of H2O and CH4 on high rank coal surface,the C30H14(nine benzene rings)representing local surface of high rank coal was constructed.The interaction between methane molecules,H2O molecules and the local surface ofcoal was analyzed by density functional theory.The results show that the adsorption of H2O molecules on the coal surface is more stable than that of methane,and the adsorption energies of H2O and CH4 with the most stable adsorption configuration is -13.23and -10.13kJ/mol,respectively.When methane molecules interact with the coal surface with pre-adsorbed water,the adsorption energy of methane molecule decreases significantly and the adsorption equilibrium distance increases,which indicates that the H2O molecules could compel CH4 molecules onto the less stable site.When two molecules(H2O and CH4)interact with the coal surface,the total energy of H2O molecule in the adsorption state and methane molecule in the desorption state is the lowest.From the molecular level,H2O molecules play a dominant role in the competitive adsorption between H2O and methane.