Hyper-parallel tempering Monte Carlo simulations of Ar adsorption in new models of microporous non-graphitizing activated carbon: effect of microporosity

Abstract

The adsorption of gases on microporous carbons is still poorly understood, partly because the structure of these carbons is not well known. Here, a model of microporous carbons based on fullerene-like fragments is used as the basis for a theoretical study of Ar adsorption on carbon. First, a simulation box was constructed, containing a plausible arrangement of carbon fragments. Next, using a new Monte Carlo simulation algorithm, two types of carbon fragments were gradually placed into the initial structure to increase its microporosity. Thirty six different microporous carbon structures were generated in this way. Using the method proposed recently by Bhattacharya and Gubbins (BG), the micropore size distributions of the obtained carbon models and the average micropore diameters were calculated. For ten chosen structures, Ar adsorption isotherms (87 K) were simulated via the hyper-parallel tempering Monte Carlo simulation method. The isotherms obtained in this way were described by widely applied methods of microporous carbon characterisation, i.e. Nguyen and Do, Horvath-Kawazoe, high-resolution α(s) plots, adsorption potential distributions and the Dubinin-Astakhov (DA) equation. From simulated isotherms described by the DA equation, the average micropore diameters were calculated using empirical relationships proposed by different authors and they were compared with those from the BG method.

New Virtual Porous Carbons Based on Carbon EDIP Potential and Monte Carlo Simulations

“…This is caused by the decrease in the percentage of pores above 1 nm. The observed changes correspond with the theoretical results obtained by Setoyama et al [54] and the results of other simulation studies [34,46]. Figure 6 presents the comparison of the APDs curves related to the simulated Ar isotherms.…”

“…The VPCs based on above mentioned Harris model were successfully used in numerous papers of the author and the co-workers for modelling the adsorption properties of activated carbons [3,[33][34][35][36][37][38][39][40][41][42][43]. Harris et al [15][16][17][18][19][20][21] proposed their model basing on the studies of typical non-graphitizing microporous carbons using high-resolution transmission electron microscopy (HRTEM).…”

“…The presence of curved fullerene-like fragments explains important properties of this type of activated carbon like their porosity and high resistance to graphitization. The fact that Harris model contains individual unbound carbon fragments (see for example figure 1 in [34]) is its main drawback. In the case of real carbons it can be expected that particular fullerene-like fragments are interconnected and form a three-dimensional structure.…”

Zeolite microporosity studied by molecular simulation

“…in which N (r, p) is the loading of adsorbed molecules at pressure p, ρ (in units of mmol/ml) is the saturation loading of Ar in pores of diameter r, P (r) is the pore size distribution in units of ml g −1Å−1 , α is the (dimensionless) affinity parameter (0.31 for Ar [53]), E 0 is the characteristic adsorption energy (kJ/mol), p 0 is the saturation vapor pressure, and n(r) is a constant that only depends on r. The total loading θ(p) of Ar in the zeolite is computed by [54,55,56,35,36],…”

Nanoscale Phenomena Occurring during Pyrolysis of Salix viminalis Wood

“…Theoretical simulation of Ar, N 2 , and CO 2 adsorption [39][40][41] in a model pore structure proved particular usefulness of Ar as a probe gas. Low temperature adsorption of N 2 was let to determine PSDs only slightly differing from Ar-based PSDs.…”