Chen Xintong, Wu Di, Miao Feng, Xiao Xiaochun, Liu Xueying, Zhai Wenbo
School of Mechanics and Engineering, Liaoning Technical University, Fuxin 123000, China.
Liaoning Key Laboratory of Mining Environment and Disaster Mechanics, Liaoning Technical University, Fuxin 123000, China.
Langmuir. 2024 Oct 22;40(42):22108-22122. doi: 10.1021/acs.langmuir.4c02480. Epub 2024 Oct 10.
Shale contains numerous organic micropores with significant potential for CO storage. To precisely evaluate the CO storage potential of shale reservoirs, it is essential to accurately quantify the adsorption of CO within these pores. This study used Grand Canonical Monte Carlo (GCMC) molecular simulations to analyze the CO adsorption behavior in organic micropores of varying sizes. The study clarified the number and width of the CO adsorption layers in micropores of various sizes and proposed a method for segmenting the multilayer adsorption structure. Additionally, the classic Ono-Kondo lattice (OK) model was extended to characterize pore-filling adsorption, incorporating solid-gas and gas-gas interactions. Accurate characterization of CO multilayer adsorption and precise calculation of CO absolute adsorption in micropores were achieved. Results indicate that CO exhibits pore-filling adsorption behavior in organic micropores, forming a multilayer adsorption structure governed by the pore size. Following symmetry principles, the adsorption layer structure in organic micropores can be simplified to a maximum of three layers. When only one adsorption layer forms, its width equals the gas-accessible pore size. For two or more layers, the width of the original layer stabilizes as additional layers form. The stable adsorption layer widths, from nearest to farthest from the pore wall, are 0.33, 0.45, and 0.39 nm. The improved OK model accurately describes CO excess and absolute adsorption isotherms across different pore sizes and calculates the CO density in each adsorption layer, showing high consistency with GCMC simulation results. These findings highlight the importance of understanding the CO multilayer adsorption structure for accurately estimating CO adsorption in organic micropores.
页岩含有大量有机微孔，具有显著的二氧化碳储存潜力。为了精确评估页岩储层的二氧化碳储存潜力，准确量化这些孔隙内二氧化碳的吸附至关重要。本研究采用巨正则蒙特卡罗（GCMC）分子模拟方法，分析了不同尺寸有机微孔中二氧化碳的吸附行为。该研究明确了不同尺寸微孔中二氧化碳吸附层的数量和宽度，并提出了一种划分多层吸附结构的方法。此外，扩展了经典的小野 - 近藤晶格（OK）模型以表征孔隙填充吸附，纳入了固 - 气和气 - 气相互作用。实现了对二氧化碳多层吸附的准确表征以及对微孔中二氧化碳绝对吸附量的精确计算。结果表明，二氧化碳在有机微孔中表现出孔隙填充吸附行为，形成了受孔径控制的多层吸附结构。根据对称原理，有机微孔中的吸附层结构最多可简化为三层。当只形成一个吸附层时，其宽度等于气体可进入的孔径。对于两个或更多层，随着额外层的形成，原始层的宽度趋于稳定。从最靠近孔壁到最远，稳定吸附层的宽度分别为0.33、0.45和0.39纳米。改进后的OK模型准确描述了不同孔径下二氧化碳的过剩吸附和绝对吸附等温线，并计算了每个吸附层中的二氧化碳密度，与GCMC模拟结果高度一致。这些发现突出了理解二氧化碳多层吸附结构对于准确估计有机微孔中二氧化碳吸附的重要性。
