Testing isotherm models and recovering empirical relationships for adsorption in microporous carbons using virtual carbon models and grand canonical Monte Carlo simulations

Abstract

Using the plausible model of activated carbon proposed by Harris and co-workers and grand canonical Monte Carlo simulations, we study the applicability of standard methods for describing adsorption data on microporous carbons widely used in adsorption science. Two carbon structures are studied, one with a small distribution of micropores in the range up to 1 nm, and the other with micropores covering a wide range of porosity. For both structures, adsorption isotherms of noble gases (from Ne to Xe), carbon tetrachloride and benzene are simulated. The data obtained are considered in terms of Dubinin-Radushkevich plots. Moreover, for benzene and carbon tetrachloride the temperature invariance of the characteristic curve is also studied. We show that using simulated data some empirical relationships obtained from experiment can be successfully recovered. Next we test the applicability of Dubinin's related models including the Dubinin-Izotova, Dubinin-Radushkevich-Stoeckli, and Jaroniec-Choma equations. The results obtained demonstrate the limits and applications of the models studied in the field of carbon porosity characterization.

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

“…The differentiation was performed numerically by the approximation of the data by the empirical function (the results were calculated with the resolution of 0.01 kJ/mol). Finally, the simulated isotherms were fitted by the Dubinin-Astakhov (DA) model, which is one of the most popular equations used in the adsorption area [36,62,63]. The DA adsorption isotherm equation may be written as [46]:…”

“…Despite this failure, the utility of Harris et al model is unquestionable. It may be treated as a good model approximation of the microstructure of real activated carbons, as proven, for example, by recovering different experimentally observed empirical correlations [36].…”

Simulating the changes in carbon structure during the burn-off process

“…geometric) pore size distribution (PSD) of the VPC models, we applied the method proposed by Bhattacharya and Gubbins [19] and used by us previously (see for example [7][8][9][10][11][12][13][14]). In this method, a uniform grid of points is generated in the simulation box (here 100 Â 100 Â 100) and for each such a point (located in a pore), the largest sphere containing this point (and situated in the pore) is found.…”

“…VPC models are often applied in carbon science and using those models together with molecular simulation techniques it is possible, for example, to analyse the mechanisms of adsorption [2][3][4][5] and immersion [6] and to check the reality of the model of 'hard' carbon proposed by Harris and co-workers [7][8][9][10][11][12][13][14]. Furthermore, the origin of different empirical relationships applied in adsorption science have been studied [9], with the model of Harris et al particularly helpful in understanding the mechanisms of adsorption of different gases (noble gases, benzene, nitrogen, carbon tetrachloride) from gaseous phase [9] as well as the mechanisms of phenol adsorption from aqueous solutions [11]. Since the model presents our conceptualisation of so-called hard activated carbon, in this study, we try to check if similar regularities are observed if one uses the models of 'soft' carbon, obtained using Molecular Dynamics (MD).…”

A molecular model for carbon black primary particles with internal nanoporosity

“…Based on the knowledge gained from experiments, simulation methods have been widely developed to model and characterize the nanostructures of carbon [33][34][35][36][37][38][39][40][41]. There are mainly two types of modeling approaches to build structures of nanoporous carbon materials, namely reconstruction methods and mimetic methods.…”