Analysis of the microporous texture of a glassy carbon by adsorption measurements and Monte Carlo simulation. Evolution with chemical and physical activation

Abstract

A mesoporous glassy carbon has been chemically (KOH) and physically (CO 2) activated in order to improve its micropore volume while preserving the well-defined mesopore network. The microporosity of the glassy carbon and the evolution of the micropore texture with activation have been studied by means of Monte Carlo simulation and gas adsorption. Micropore size distributions obtained from simulated adsorption isotherms on slit-shaped pores revealed different accessibilities of methane and nitrogen to the microporous texture of the original sample, indicating the presence of constrictions in the micropore network. Both activating agents are able to increase the micropore volume generating new micropores, although KOH showed to be more effective. While CO 2 treatment preserved some hindrances to the access of nitrogen molecules to the micropores, KOH activation generates a more accessible micropore network. Therefore, chemical activation by KOH is a suitable way to increase the adsorption capacity of glassy carbons while preserving the mesoporous structure. Molecular simulation of adsorption linked to experimental adsorption of different gases, has proven to give very satisfactory results in analysing the evolution of the micropore texture and accessibility of carbon materials by different activation treatments.