(645b) Deformation of Nanoporous Carbons Induced By Multicomponent Adsorption: Insight from the SAFT-DFT Model

Predicting adsorption and mechanical properties of nanoporous carbons is of paramount importance for numerous practical applications, such as mixture separations, electrodes and supercapacitors, gas storage, carbon capture, and enhanced natural gas recovery. Most industrial applications involve multi-component adsorption that is complicated in the case of compliant nanoporous carbons, which expand and contract upon adsorption and desorption of guest molecules.

In this work, we consider the deformation of nanoporous carbons during the adsorption of mixtures, focusing on the specific context of carbon dioxide displacement of natural gas from shale and coal. ^[1] We use the density functional theory (DFT) augmented by the perturbed chain statistical associating fluid theory (SAFT) ^[2] to model adsorption of fluid mixtures in carbon nanopores at geologically relevant temperatures and pressures. The SAFT-DFT model allows for calculating the adsorption stress that is the driving force of adsorption-induced deformation. ^[3] First, we consider the case-study system of adsorption of methane and carbon dioxide mixtures in pores of various sizes and calculate the adsorption stress as the function of the fluid composition. Next, we explore the mixtures of carbon dioxide and alkanes and determine how the hydrocarbon chain length affects the carbon dioxide co-adsorption and the stress exerted on the carbon matrix. Calculations are performed in the wide range of pressures and temperatures characteristic to geological conditions.

1. Corrente, N. J.; Zarȩbska, K.; Neimark, A. V., Deformation of Nanoporous Materials in the Process of Binary Adsorption: Methane Displacement by Carbon Dioxide from Coal. J. Phys. Chem. C 2021, 125 (38), 21310-21316.
2. Liu, J.; Wang, L.; Xi, S.; Asthagiri, D.; Chapman, W. G., Adsorption and phase behavior of pure/mixed alkanes in nanoslit graphite pores: an iSAFT application. Langmuir 2017, 33 (42), 11189-11202.
3. Ravikovitch, P. I.; Neimark, A. V., Density functional theory model of adsorption deformation. Langmuir 2006, 22 (26), 10864-10868.