Adsorption of Carbon Dioxide, Water and Their Mixtures in Nanoporous Carbons: Experiment and Molecular Simulation

The adsorption of carbon dioxide and in nanoporous carbons in presence of water has been studied using experiments and molecular simulations in a previous study1.This work reported a good agreement between experiments and molecular simulations in terms of effect of water on the pore filling mechanism. However, differences were observed regarding the amounts adsorbed and the isosteric heats of adsorption. These discrepancies have been attributed to a too homogeneous (chemically and geometrically) model to describe the materials. In order to improve adequacy between experimental and simulated data, two heterogeneous model of carbon, wherein oxygenated groups have been added, have been implemented in this study.
The first model consists in a porous material established from a box full of graphene sheets wherein spherical holes of various diameters have been created. The models have been established in order to have the same density and porous volume as the experimental activated carbon used. In a second time, Hydroxyl and carboxyl groups have been added in accordance with the compositions of the activated carbon to describe more accurately the adsorption of water and the effect on the adsorption of carbon dioxide. The second model is the one obtained by RMC by Jain et al. (2005)2 wherein carboxyl and hydrocarbon groups has been added to obtained the composition given in Jain et al.(2006)3.
The results show improvements of the ability of the model to describe the adsorption of CO2 in an activated carbon especially in terms of isosteric heats of adsorption. The pore filling mechanism of the adsorption of water has been correctly described on the grafted models. To increase the number of comparison criteria, molecular simulations and experimental measurements of N2 adsorption at 77 K have been carried out.