Structure modeling of activated carbons used for simulating methane adsorption – A review

Activated carbons (ACs) are highly porous materials with a broad range of applications in industry such as gas storage, water and air purification, gas separation, and catalysis. The microstructure for ACs is still not clearly known in spite of their wide industrial uses. There have been efforts to describe the structure of activated carbons experimentally in relation to its methane adsorption characteristics. In this review, it is assumed that natural gas is sorely composed of CH4 for simplicity (because CH4 is the major component, >90%). Experimental means to unveil the microstructure and many other properties for these ACs have some limitations, to overcome these limitations, ACs structural modeling and simulation become very important to match the properties with the desired methane adsorption characteristics. The major challenge that methane adsorption simulation faces for so long, is the lack of realistic AC models. This paper reviews the current efforts to develop the realistic AC models for methane adsorption, most of the built models are based on experimental carbon structural findings from the previous studies. The structural parameters including pore size distribution (PSD), specific surface area (SSA), pore volume and extent of curvature in the carbon materials and their role to methane adsorption are discussed. The role of chemical properties, such as presence of functional groups and the nature of the functional groups to the adsorption properties of methane, are also introduced. Different pore morphologies (such as slit pore, platelet, spherical, etc.) are studied with their effect on methane adsorption and presented too. It is found that each of the mentioned parameters has its own bearing to methane adsorption. Furthermore, this work analyzes different current techniques used in modeling natural gas adsorption, and the mechanisms are able to reproduce the specific carbon materials for a certain desired set of adsorption characteristic. Some future works are also recommended in this area, so that better representations of ACs can be obtained for methane storage purposes.