Mechanistic insights into confined methane adsorption in carbon nanopores at the molecular level

Abstract

For methane adsorption, little attention has been given to the comprehensive effect of fluid-wall and fluid–fluid interactions in confined carbon pores. The simplified local density (SLD) model is suitable for confined adsorption studies. However, it has not been unified due to the various utilizations of the equation of states (EOSs). Eighteen selected cubic EOSs were modified, including the first given expressions of confined attractive parameters with the (3/8)σff assumption. After comparing 36 SLD models, the Redlich-Kwong-Soave-type EOS and the (3/8)σff assumption were recommended for accurate confined adsorptions. The confined effect has little impact on fluid–fluid repulsion. As the size of carbon nanopores decreases, the confined adsorption is negatively affected by the decreasing fluid–fluid attractive potential and positively affected by the growing fluid-wall interactive potential. When nanopores are larger than 3 nm, the adsorption is not affected by the confined effect. Our research provided novel mechanistic insights into confined methane adsorption.