Competitive adsorption of a binary CO 2 –CH 4 mixture in nanoporous carbons: effects of edge-functionalization

Zhao

et al. 2018

Energy Tech

Capturing CO2 from flue gas is recognized as a key process to improve the environment, therefore, developing a new cost‐effective sorbent is crucial. In this study, the calcite slit‐nanopores with various pore sizes ranging from ∼5 Å to ∼30 Å were constructed, the grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were used to examine the microscopic behaviors of CO2 and N2 in calcite slit‐nanopores. Diverse adsorption layer structures for CO2 and N2 molecules as single component in calcite slit‐nanopores are found as the pore size changing, of which the CO2 represents a transformation from single adsorption layer to five adsorption layers, while N2 represents a variation from single adsorption layer to three adsorption layers. Meantime, different adsorption orientations of CO2 and N2 molecules adsorbed close onto the calcite pore surface are also found. Moreover, strong competitive adsorption of CO2 over N2 is found due to the different interactions between CO2 and N2 molecules with the calcite pore surface, the capacity of competitive adsorption decreases with the pore size increasing. The self‐diffusion and isosteric heat of CO2 and N2 molecules in calcite slit‐nanopores are also examined to demonstrate the different adsorption intensities of gases in calcite slit‐nanopores. This work demonstrates the detailed microscopic behaviors of CO2 and N2 molecules in calcite slit‐nanopores, which not only enriches the theoretical knowledge about gases adsorption in calcite slit‐nanopores, but also gives out the feasibility of capturing CO2 from flue gas by calcite‐based substances.

Section: Resultssupporting

confidence: 76%

Exploration of Capturing CO₂ from Flue Gas by Calcite Slit‐Nanopores: A Computational Investigation

Zhao

et al. 2018

Energy Tech

“…For CH 4 , the gas molecule is trapped in the concave sites of the pore surface. This is because, in contrast to CO 2 , the CH 4 molecule is tetrahedral with a C atom in the center surrounded by four H atoms, which are repelled by the H atoms of the surface hydroxyl groups, hence the interactions between CH 4 molecules and the pore surface are much weaker than those of CO 2 (Table ). Therefore, the rough surface plays another factor in addition to the adsorption interactions between the gas molecule and the pore surface.…”

Section: Resultsmentioning

confidence: 99%

Simulation to Enhance Shale Gas Recovery Using Carbon Dioxide in Silica Nanopores with Different Sizes

Zhao

et al. 2017

Energy Tech

An understanding of molecular behavior on a microscopic level is always important not only to find out the natural principles but also to decide how to solve problems in applications. In this study, the grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were employed to investigate the adsorption and diffusion properties of CH4 and CO2 in silica nanopores with different sizes, and the displacement of residual CH4 in silica nanopores by CO2 at a constant temperature of 323 K and various pressures was studied. The microscopic molecular states of the adsorbed CH4 and CO2 in nanopores of various sizes are different. The competitive adsorption of CO2 over CH4 occurs broadly because of the different intensity of interactions between the gases molecules and the pore surface, of which the degree decreases with the increase of the pore size. An effective displacement process of residual adsorbed CH4 by CO2 was performed, and it is found that the displacement is enhanced with the increase of the CO2 bulk pressure and that the pore size has a significant influence on the displacement. According to the results, CO2 capture and storage (CCS) and the enhancement of CH4 recovery could be achieved at the same time in silica nanopores. This work provides microscopic information on the molecular behavior of CH4 and CO2 in silica nanopores and testifies to the efficiency of the displacement of CH4 by CO2 in silica nanopores with various sizes to provide useful guidance for applications in the enhancement of shale gas recovery by CO2.

“…Weniger et al showed that as the increase of vitrinite content, the amount of adsorbed carbon dioxide decreases significantly, while the amount of adsorbed methane remains unchanged (Figure ). Lu et al studied binary gas adsorption on nanoporous carbon with different functional groups . It was found that the difference of molecular functional groups significantly affects the selectivity factor.…”

Section: Factors Affecting the Adsorption Of Tcgmentioning

confidence: 99%

A review of gas transport and adsorption mechanisms in two‐component methane‐carbon dioxide system

Guo

et al. 2019

Int J Energy Res

Summary Injecting carbon dioxide for shale gas recovery enhancement (CO2‐ESGR) is an effective method to improve gas production and also realize the CO2 geosequestration. In the CO2‐ESGR system, there are two‐component gases (TCG) coexisted. The gas transport and adsorption mechanisms are different from the single‐component gas system. However, most of current work is still focused on single‐component gas (ie, methane). Many mechanisms have not been considered in the study of CO2‐ESGR study. In order to conduct reliable numerical simulation for CO2‐ESGR, a clear understanding of the transport and adsorption mechanisms for TCG system is necessary. In this review, we focused on two key issues regarding CO2‐ESGR: the fluid transport and competitive adsorption. The fundamental mechanisms and models for pure gas and TCG transport have been comprehensively summarized. The adsorption models for TCG system have been reviewed and analyzed. Models such as extended Langmuir model, ideal adsorption solution model, and lattice density functional model have been compared. Also, the factors affecting the competitive adsorption of TCG in shale have been illustrated. The main factors include organic matter content, shale composition, pore structure, water content, and pressure. At last, the problems existed in current research of transport and adsorption models for TCG have been analyzed. The issues that are necessary to be considered in CO2‐ESGR technology have been proposed so that more accurate numerical simulation and more reliable production prediction can be achieved.