A modified model for estimating excess adsorption of methane in moist nanoporous silica

Excess adsorption is usually used to measure the adsorption capacity of porous materials. Negative excess adsorption, which is unphysical and deviates from experiments, is noted in the usual computational model for methane adsorption in moist silica with nano-sized pores. Water-occupied volume, which is usually neglected in macro-porous models, is responsible for such deviations. A modified model for computing excess adsorption of methane in moist and nano-porous is proposed by taking into account the effect of water-occupied volume, which becomes significant in a small pore with a high water content. The modified model produces positive excess adsorption that matches better with available experiments. The proposed modification would be helpful for the prediction of methane reserves and productions.