Simulation study on the effect of pore structure and surface curvature of activated carbon on the adsorption and separation performance of CO2 /N2

Abstract

In this paper, the Grand Canonical Monte Carlo (GCMC) method was used to explore the effects of four pore structures (disordered pore, wedge pore, carbon nanotube and slit pore structures) and surface curvature of activated carbon on the adsorption and separation of CO2/N2. On the whole, carbon nanotubes have the greatest selectivity for CO2, followed by disordered pores, wedge pores and slit pores. The effect of pore structure on the interaction energy of gas molecules is similar to that of selectivity, in which the fluid-solid potential energy between adsorbates and adsorbents plays an important role. Due to the different affinity between adsorbate molecules and activated carbon, CO2 with high affinity is more sensitive to the change of pore size. Therefore, under high pressure, the density of CO2 in the slit pore is greater than that in the wedge pore. However, N2 with poor affinity is limited by the surface area, resulting in the density of it in the wedge pore is always higher than that in the slit pore. Although the existence of non-six membered corannulene rings in activated carbon can’t always cause the increase of specific surface area, the surface curvature of activated carbon caused by it can increase strong energetically adsorption sites. Hence, the surface curvature plays a positive role in the adsorption density, interaction energy and CO2 selectivity. The discovery of CO2/N2 adsorption and separation at the molecular level is expected to provide valuable insights.