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页岩中干酪根结构简化为不同碳氧比石墨结构,利用巨正则蒙特卡罗模拟方法研究甲烷分子在不同碳氧比石墨中吸附行为,讨论了孔径、温度、含水量和二氧化碳对甲烷在不同碳氧比石墨中吸附行为的影响,在此基础上分析碳氧比变化对甲烷吸附行为影响,揭示了甲烷在不同碳氧比石墨中的微观吸附机理以及温度、水分及二氧化碳对甲烷吸附行为的影响及其微观作用机理.研究结果表明:相同碳氧比中,当孔径从1nm增大到20nm时,甲烷在碳氧比为4孔中的平均等量吸附热从19.65kJ/mol减小为7.88kJ/mol,且甲烷过剩吸附量随微孔孔径增大而增大,而随中孔孔径增大而减小;相同孔径中,当碳氧比从4增加到20时,甲烷在孔径1nm中的平均等量吸附热从19.65kJ/mol减小为16.39kJ/mol,且甲烷过剩吸附量随着碳氧比增大而减小;当温度从313K升高到373K时,甲烷在碳氧比为4孔中的吸附逐渐由能量较低的吸附位向能量较高的吸附位转移,甲烷等量吸附热从12.76kJ/mol减小为12.16kJ/mol,造成甲烷过剩吸附量降低;水分子在孔中受到范德华力和静电能共同作用使其聚集在含氧官能团附近,且水分子占据了甲烷分子吸附空间,造成甲烷过剩吸附量降低;在多元组分竞争吸附中,不同碳氧比石墨对二氧化碳的吸附能力大于甲烷.甲烷在气相中摩尔分数降低、甲烷吸附位的变化以及甲烷吸附空间减小将导致了甲烷吸附能力降低.
The kerogen structure in shale is simplified to different carbon / graphite structures. The adsorption properties of methane molecules in different carbon / graphite ratio graphite are studied by using the method of giant regular Monte Carlo simulation. The effects of pore size, temperature, water content and carbon dioxide on the adsorption of methane The influence of carbon and oxygen ratio on the adsorption behavior of graphite was analyzed. Based on the analysis of the influence of the change of carbon / oxygen ratio on the adsorption behavior of methane, the microscopic adsorption mechanism of methane on different carbon / graphite ratio and the effect of temperature, moisture and carbon dioxide on methane adsorption were revealed The results show that when the pore diameter increases from 1nm to 20nm, the average isothermal adsorption heat of methane decreases from 19.65kJ / mol to 7.88 kJ / mol, and the excess methane adsorption increases with the increase of pore size, but decreases with the increase of pore size. When the ratio of carbon to oxygen is increased from 4 to 20 in the same pore size, The average isothermal adsorption heat decreased from 19.65 kJ / mol to 16.39 kJ / mol, and the excess methane adsorption decreased with the increase of carbon to oxygen ratio. When the temperature increased from 313 K to 373 K, The adsorption ratio for the 4 wells is gradually increased by the energy The low adsorption sites shifted to the higher energy adsorption sites, and the equivalent heat of methane adsorption decreased from 12.76kJ / mol to 12.16kJ / mol, resulting in a decrease in the excess methane adsorption. The water molecules in the pores were subjected to van der Waals forces and electrostatic energy Which causes it to accumulate near the oxygen-containing functional groups, and the water molecules occupy the adsorbed space of methane molecules, resulting in a decrease of the excess methane adsorption capacity. In the multi-component competitive adsorption, the adsorption capacities of different carbon and carbon oxides to carbon dioxide are higher than those of methane. The decrease of the molar fraction in the gas phase, the change of methane adsorption sites and the reduction of methane adsorption space will lead to the decrease of methane adsorption capacity.