石英吸附甲烷的蒙特卡罗研究

利用巨正则蒙特卡罗模拟方法对甲烷在石英中吸附行为进行了研究，并讨论了不同孔径、不同温度、不同含水量和不同组成对甲烷在石英中吸附行为的影响。研究结果表明：甲烷超额吸附量随着压力的增大而先上升后下降，且随着孔径增大逐渐减小；甲烷与石英相互作用能随着压力增大或孔径减小而减小，说明甲烷在孔中吸附逐渐由能量较高的吸附位向能量较低的吸附位转移；随着温度升高，甲烷等量吸附热减小，甲烷在孔中吸附逐渐由能量较低的吸附位向能量较高的吸附位转移，造成甲烷在石英孔中吸附能力降低，导致甲烷吸附量减小；水分子在孔中以定向方式占据着石英孔壁面，且受到范德华力和静电能共同作用在孔中以堆积形式存在；随着含水量增加，甲烷分子在孔中吸附位并没有随着发生变化，即水分子只占据甲烷分子吸附空间，造成甲烷吸附量减小；气体与石英间相互作用能量大小顺序为氮气>甲烷>二氧化碳，则石英上吸附能力大小的顺序为二氧化碳>甲烷>氮气；多组分竞争吸附中，甲烷在气相中摩尔分数降低、甲烷分子吸附位变化以及甲烷吸附空间减小，综合作用导致了甲烷吸附量减小。

Adsorption of methane in quartz by Grand Canonical Monte Carlo simulation

The adsorption behaviors of methane in quartz have been investigated by using Grand Canonical Monte Carlo simulations,and the influences of different pore sizes,different temperatures,different water contents and different compositions of the methane adsorption on quartz have been discussed.The results show that the excess adsorption of methane increased firstly and then decreased with the increase of the pressure,and increased with the decrease of the pore size.The interaction energy between methane and quartz decreased with the increase of pressure or the decrease of pore size,indicating that the adsorption sites of methane adsorption on the quartz transferred from the higher energy to the lower energy.With the increase of temperature,the isosteric heats of the methane decreased and the adsorption sites of methane adsorption on the quartz transferred from higher energy to lower energy,resulting in the decrease of methane adsorption capacity.The water molecular in the pore of quartz occupied the pore wall in directional way,which was acted upon by the van der Waals force and Coulomb force,resulting in the molecular water accumulation in the pores.With the increase of temperature,the adsorption sites of methane did not change,indicating that the molecular water only occupy adsorption space of the methane,resulting in the decrease of methane adsorption capacity.The interaction energy between gas and quartz decreased in the following order:nitrogen >methane >carbon dioxide,indicating that the adsorption capacity decreased in the following order:carbon dioxide >methane > nitrogen.The mole fraction of nitrogen or carbon dioxide in the gas phase increased,the mole fraction of gaseous methane would decrease,the adsorption sites of methane would change and the adsorption space of methane would deduce,resulting in the decrease of methane adsorption capacity.