(339f) Monte Carlo Simulation of High Pressure CO2 Adsorption Isotherms for Characterization of Micro-Mesoporous Carbons

CO₂ has been proposed as probe molecule to characterize micro-mesoporous carbons due to its ability to adsorb at elevated temperatures, which allows for higher diffusion rates and penetration into narrow micropores. Recently, a quenched solid density functional theory (QSDFT) kernel of isotherms was developed [1] for the adsorption of CO₂ at elevated temperature and pressure, for the first time enabling the characterization of both the micro- and mesoporosity of a carbon material in a single measurement. While this effort represents a significant improvement in the capabilities of computational methods for carbon characterization using CO₂ adsorption, DFT cannot completely capture the subtler properties of CO₂ that are a product of its non-spherical molecular geometry, nor the effects of heterogeneous pore structure present in amorphous carbons.

This work presents a novel adsorption model for CO₂ adsorption in heterogeneous (rough) carbon nanopores at 273 K, calculated using Hybrid Reverse (HR) and Grand Canonical (GC) Monte Carlo. The models of slit-shaped and cylindrical pores are developed using heterogeneous pore walls, which molecular structure is fitted with HRMC to the radial distribution function of a reference amorphous carbon. Validation of model parameters is done by: (1) vapor-liquid equilibrium calculations in a bulk system; (2) prediction of adsorption isotherm on graphite surface; (3) comparison of the isotherms with experimental data and the QSDFT isotherms. The calculated isotherms are combined into adsorption kernels and used to generate the surface area, pore volume, and pore size distribution of several characteristic carbon materials.

1. Cimino R., C.K., Thommes M. and Neimark A. V., Characterization of Hierarchically Structured Porous Carbons by High Pressure CO2 Adsorption.