Adsorption of argon from sub- to supercritical conditions on graphitized thermal carbon black and in graphitic slit pores: A grand canonical Monte Carlo simulation study

Abstract

Grand canonical Monte Carlo simulation of argon adsorption at the surface of silica nanopores: Effect of pore size, pore morphology, and surface roughness J. Chem. Phys. 120, 2913 (2004) In this paper we consider the adsorption of argon on the surface of graphitized thermal carbon black and in slit pores at temperatures ranging from subcritical to supercritical conditions by the method of grand canonical Monte Carlo simulation. Attention is paid to the variation of the adsorbed density when the temperature crosses the critical point. The behavior of the adsorbed density versus pressure ͑bulk density͒ shows interesting behavior at temperatures in the vicinity of and those above the critical point and also at extremely high pressures. Isotherms at temperatures greater than the critical temperature exhibit a clear maximum, and near the critical temperature this maximum is a very sharp spike. Under the supercritical conditions and very high pressure the excess of adsorbed density decreases towards zero value for a graphite surface, while for slit pores negative excess density is possible at extremely high pressures. For imperfect pores ͑defined as pores that cannot accommodate an integral number of parallel layers under moderate conditions͒ the pressure at which the excess pore density becomes negative is less than that for perfect pores, and this is due to the packing effect in those imperfect pores. However, at extremely high pressure molecules can be packed in parallel layers once chemical potential is great enough to overcome the repulsions among adsorbed molecules.

On the anatomy of the adsorption heat versus loading as a function of temperature and adsorbate for a graphitic surface

“…Usually we correct the cross-well depth of interaction energy with a factor to account for the deviation from this rule [10][11][12][13]. For xenon dealt with in this paper, A = B = 0 and C = D = 1.…”

A grand canonical Monte Carlo simulation study of argon and krypton confined inside weakly attractive slit pores

“…This formation of layers occurs only inside the attractive pores at given conditions of pressure, temperature, pore attractiveness and pore size but is not observed in the hard wall pores without uniform potential at the same conditions of pressure, temperature and pore size. Do and Do [42] also noted the increase in the number of layers formed with slit height for LJ argon adsorbed in Steele wall pores at high pressures though lesser number of layers were observed at lower pressures inside the wider pores. The density profiles for pores with 1 wf =k B ¼ 4:81 K have not been reported in the figures for purposes of clarity and also not discussed in the text.…”

“…Research on adsorption of argon inside pores has been extensively carried out by the Do group at the University of Queensland, Australia using GCMC simulations. [41] The influence of pressure, temperature and slit height on the behaviour of argon confined in graphitic slit pores has been studied by Do and Do [42]. GCMC predictions of excess pore density and density profiles of argon in graphitic slit pores are also reported by Do et al [43].…”

Effects of confinement on the molar enthalpy of argon adsorption in graphitic cylindrical pores: A grand canonical Monte Carlo (GCMC) simulation study

“…This is because the bulk gas density changes significantly for a small change in pressure near the critical point [41]. As the temperature is increased, the maximum of the isotherm is less sharp (298 and 400 K) because of the smaller change in the bulk gas density with pressure.…”