Liu Jinlu, Xi Shun, Chapman Walter G
Department of Chemical and Biomolecular Engineering , Rice University , 6100 Main Street , Houston , Texas 77005 , United States.
Langmuir. 2019 Jun 18;35(24):8144-8158. doi: 10.1021/acs.langmuir.9b00410. Epub 2019 May 28.
CO competitive sorption with shale gas under various conditions from simple to complex pore characteristics is studied using a molecular density functional theory (DFT) that reduces to perturbed chain-statistical associating fluid theory in the bulk fluid region. The DFT model is first verified by grand canonical Monte Carlo simulation in graphite slit pores for pure and binary component systems at different temperatures, pressures, pore sizes, and bulk gas compositions for methane/ethane with CO. Then, the model is utilized in multicomponent systems that include CH, CH, and C3+ components of different compositions. It is shown that the selectivity of CO decreases with increases in temperature, pressure, nanopore size, and average molecular weight of shale gas. Extending the model to more realistic situations, we consider the impact of water present in the pore and consider the effect of permeation of fluid molecules into the kerogen that forms the pore walls. The water-graphite interaction is calibrated with contact angle from molecular simulation data from the literature. The kerogen pore model prediction of gas absolute sorption is compared with experimental and molecular simulation values in the literature. It is shown that the presence of water reduces the CO adsorption but improves the CO selectivity. The dissolution of gases into the kerogen matrix also leads to the increase in CO selectivity. The effect of kerogen type and maturity on the gas sorption amount and CO selectivity is also studied. The associated mechanisms are discussed to provide fundamental understanding for gas recovery by CO.
利用分子密度泛函理论（DFT）研究了在从简单到复杂孔隙特征的各种条件下，CO与页岩气的竞争吸附，该理论在体相流体区域简化为微扰链统计缔合流体理论。首先通过巨正则蒙特卡罗模拟在石墨狭缝孔隙中，针对不同温度、压力、孔径以及甲烷/乙烷与CO的体相气体组成的纯组分和二元组分系统，对DFT模型进行了验证。然后，将该模型应用于包含不同组成的CH₄、C₂H₆和C₃⁺组分的多组分系统。结果表明，CO的选择性随着温度、压力、纳米孔径以及页岩气平均分子量的增加而降低。将模型扩展到更实际的情况，我们考虑了孔隙中存在的水的影响，并考虑了流体分子渗透到形成孔壁的干酪根中的影响。利用文献中分子模拟数据的接触角对水 - 石墨相互作用进行了校准。将干酪根孔隙模型对气体绝对吸附的预测与文献中的实验值和分子模拟值进行了比较。结果表明，水的存在降低了CO的吸附，但提高了CO的选择性。气体溶解到干酪根基质中也导致CO选择性增加。还研究了干酪根类型和成熟度对气体吸附量和CO选择性的影响。讨论了相关机制，为通过CO进行气体回收提供基本认识。
