H_2O和CH_4在煤表面竞争吸附机理
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摘要
为从微观上探讨H_2O和CH_4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 H_2O and CH_4 on high rank coal surface,the C_(30)H_(14)(nine benzene rings) representing local surface of high rank coal was constructed.The interaction between methane molecules,H_2O molecules and the local surface of coal was analyzed by density functional theory.The results show that the adsorption of H_2O molecules on the coal surface is more stable than that of methane,and the adsorption energies of H_2O and CH_4 with the most stable adsorption configuration is -13.23 and -10.13 kJ/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 H_2O molecules could compel CH_4 molecules onto the less stable site.When two molecules(H_2O and CH_4) interact with the coal surface,the total energy of H_2O molecule in the adsorption state and methane molecule in the desorption state is the lowest.From the molecular level,H_2O molecules play a dominant role in the competitive adsorption between H_2O and methane.
In order to study the mechanism of competitive adsorption of H_2O and CH_4 on high rank coal surface,the C_(30)H_(14)(nine benzene rings) representing local surface of high rank coal was constructed.The interaction between methane molecules,H_2O molecules and the local surface of coal was analyzed by density functional theory.The results show that the adsorption of H_2O molecules on the coal surface is more stable than that of methane,and the adsorption energies of H_2O and CH_4 with the most stable adsorption configuration is -13.23 and -10.13 kJ/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 H_2O molecules could compel CH_4 molecules onto the less stable site.When two molecules(H_2O and CH_4) interact with the coal surface,the total energy of H_2O molecule in the adsorption state and methane molecule in the desorption state is the lowest.From the molecular level,H_2O molecules play a dominant role in the competitive adsorption between H_2O and methane.
引文
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[2]俞启香,程远平.矿井瓦斯防治[M].北京:中国矿业大学出版社,2012.YU Qi-xiang,CHENG Yuan-ping. Mine gas control[M]. Beijing:China University of Mining and Technology Press,2012.
[3] ZHANG Xiang-liang,LIN Bai-quan,ZHU Chuan-jie,et al. Improvement of the electrical disintegration of coal sample with different concentrations of Na Cl solution[J]. Fuel,2018,222:695-704.
[4] LIN Bai-quan,ZHANG Xiang-liang,YAN Fa-zhi,et al.Improving the conductivity and porosity of coal with Na Cl solution for high-voltage electrical fragmentation[J]. Energy and Fuels,2018,32(4):5010-5019.
[5]熊祖强,袁广玉,陶广美.综放工作面注水降尘技术[J].西安科技大学学报,2013,33(4):394-399.XIONG Zu-qiang,YUAN Guang-yu,TAO Guang-mei.Water injection and dust control technology in fully mechanized top coal caving face[J]. Journal of Xi’an University of Science and Technology,2013,33(4):394-399.
[6]肖知国,王兆丰.煤层注水防治煤与瓦斯突出机理的研究现状与进展[J].中国安全科学学报,2009,19(10):150-158.XIAO Zhi-guo,WANG Zhao-feng. Research status and progress of coal seam water injection to prevent coal and gas outburst[J]. Chinese Journal of Safety Science,2009,19(10):150-158.
[7] ZHAO Yang-sheng,QU Fang,WAN Zhi-jun,et al. Experimental investigation on correlation between permeability variation and pore structure during coal pyrolysis[J]. Transport in Porous Media,2010,82(2):401-412.
[8]冯增朝,赵东,赵阳升.块煤含水率对其吸附性影响的试验研究[J].岩石力学与工程学报,2009,28(A02):3291-3295.FENG Zeng-zhao,ZHAO Dong,ZHAO Yang-sheng. Experimental study on the impact of water ratio to adsorption on lump coal[J]. Chinese Journal of Rock Mechanics and Engineering,2009,28(A02):3291-3295
[9]李晓华,王兆丰,李青松,等.水分对新景矿3号煤层瓦斯解吸规律的影响[J].煤炭科学技术,2011,39(5):47-50.LI Xiao-hua,WANG Zhao-feng,LI Qing-song,et al.Moisture affected to gas desorption law of No. 3 seam in Xinjing mine[J]. Coal Science and Technology,2011,39(5):47-50.
[10] Day Stuart,Sakurovs Richard,Weir Steve. Supercritical gas sorption on moist coals[J]. International Journal of Coal Geology,2008,74(3):203-214.
[11]相建华,曾凡桂,梁虎珍,等. CH4/CO2/H2O在煤分子结构中吸附的分子模拟[J].中国科学(地球科学),2014,44(7):1418-1428.XIANG Jian-hua,ZENG Fan-gui,LIANG Hu-zhen,et al. Molecular simulation of the CH4/CO2/H2O adsorption onto the molecular structure of coal[J]. Scientia Sinica(Terrae),2014,44(7):1418-1428.
[12]夏阳超,刘晓阳,刘生玉.褐煤表面含氧官能团对水分子的吸附机理[J].煤炭转化,2016,39(4):1-5.XIA Yang-chao,LIU Xiao-yang,LIU Sheng-yu. Adsorption mechanism of water molecules onto oxygen containing functional groups of lignite[J]. Coal Conversion,2016,39(4):1-5.
[13] ZHANG Jun-fang,Clennell M B,Dewhurst D N,et al.Combined monte carlo and molecular dynamics simulation of methane adsorption on dry and moist coal[J].Fuel,2014,122(15):186-197.
[14]王宝俊,凌丽霞,赵清艳,等.气体与煤表面吸附作用的量子化学研究[J].化工学报,2009,60(4):995-1000.WANG Bao-jun,LING Li-xia,ZHAO Qing-yan,et al.Quantum chemistry study on adsorption of gas on coal surface[J]. Journal of Chemical Industry and Engineering Society of China,2009,60(4):995-1000.
[15] XU He,CHU Wei,HUANG Xia,et al. CO2adsorptionassisted CH4desorption on carbon models of coal surface:A DFT study[J]. Applied Surface Science,2016,375:196-206.
[16] FU Yu-tong,SONG Yu. CO2-adsorption promoted CH4-desorption onto low-rank coal vitrinite by density functional theory including dispersion correction(DFT-D3)[J]. Fuel,2018,219:259-269.
[17] ZHOU Ya-nan,SUN Wen-jing,WEI Chu,et al. Theoretical insight into the enhanced CH4desorption via H2O adsorption on different rank coal surfaces[J]. Journal of Energy Chemistry,2016,25(4):677-682.
[18] Grimme S,Ehrlich S,Goerigk L. Effect of the damping function in dispersion corrected density functional theory[J]. Journal of Computational Chemistry,2011,32(7):1456-1465.
[19] Grimme S,Antony J,Ehrlich S,et al. A consistent and accurate ab initio parametrization of density functional dispersion correction(DFT-D)for the 94 elements H-Pu[J]. Journal of Chemical Physics,2010,132(15):154104.
[20] Sony P,Puschnig P,Nabok D,et al. Importance of van der Waals interaction for organic molecule-metal junctions:adsorption of thiophene on Cu(110)as a prototype[J]. Physical Review Letters,2007,99(17):176401.
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