New insights into the ideal adsorbed solution theory

Abstract

The GCMC technique is used for simulation of adsorption of CO2-CH4, CO2-N2 and CH4-N2 mixtures (at 298 K) on six porous carbon models. Next we formulate a new condition of the IAS concept application, showing that our simulated data obey this condition. Calculated deviations between IAS predictions and simulation results increase with the rise in pressure as in the real experiment. For the weakly adsorbed mixture component the deviation from IAS predictions is higher, especially when its content in the gas mixture is low, and this is in agreement with the experimental data. Calculated activity coefficients have similar plots to deviations between IAS and simulations, moreover obtained from simulated data activity coefficients are similar qualitatively as well as quantitatively to experimental data. Since the physical interpretation of activity coefficients is completely lacking we show for the first time that they can be described by the formulas derived from the expression for G(ex) for the ternary mixture. Finally we also for the first time show the linear relationship between the chemical potentials of nonideal and ideal solutions and the reduced temperature of interacting mixture components, and it is proved that the deviation from ideality is larger if adsorption occurs in a more microporous system.

Structural prediction of graphitization and porosity in carbide-derived carbons

“…EDIP has been successful in MD simulations of graphitization processes [42,43,44,45,46] and in HRMC and MC models of nanoporous carbon. [36,30,47,31] To bridge the gap between the experimental and simulation timescale we develop an Arrhenius framework which allows correlation between the experimental and simulation temperatures. In agreement with experiments, we observe that at low temperature the structures are disordered and as temperature increases graphitic fragments develop, forming stacks at the highest temperatures.…”

Experimental and Neural Network Modeling of Partial Uptake for a Carbon Dioxide/Methane/Water Ternary Mixture on 13X Zeolite

“…Each of these theoretical models has their own limitations, for example, IAST is based on the assumption that the adsorbate mixture behaves like an ideal solution and, therefore, it is inappropriate to predict nonideal adsorptions. Frequently, IAST becomes less accurate at high densities of the adsorbate phases, even for mixtures that are relatively ideal . In the case of nonideal solution theories (such as RAST and VSM), additional adsorption data are necessary to obtain reliable adsorption predictions of multicomponent systems.…”

“…Frequently,I ASTb ecomes less accurate at high densities of the adsorbate phases, even for mixtures that are relatively ideal. [8][9][10] In the case of nonideal solutiont heories( such as RAST and VSM), additional adsorption data are necessary to obtain reliablea dsorption predictions of multicomponent systems.T here is al ack of adequatee xperimental data on ternary and higher component mixtures, [11] and as light changeo ft he adsorbent generally requires ac hangeo fp arameters in the present adsorption models.A lso,t here is certainly insufficient data reported on the effect of operating conditions and adsorption parameters, in terms of temperature,p ressure,a nd initial mixture compositions,e specially if water vapor is involved in the mixture. [12][13][14] TheG ERG (Groupe EuropØen de Recherches Gazires) equationofs tate enables the calculationoft hermal and caloric properties for natural gases and other mixturest hat con-sist of 18 components,t hat is,C H 4 ,N 2 ,C O 2 ,e thane,p ropane, n-butane,i sobutane, n-pentane isopentane, n-hexane, n-heptane, n-octane,H 2 ,O 2 ,C O, H 2 O, He,a nd Ar, in addition to some of the heavy hydrocarbon components,w hich exist in natural gas mixtures,a nd hydrogen sulfide,w hich exists in some streams.W ilhelmsen et al [15] evaluated the predictions from Soave-Redlich-Kwong (SRK) with Penelouxs hift, Peng-Robinson (PR), Lee-Kesler, (State R&D Program for Utilization of Natural Gas) SPUNG/SRK EoS,a nd the multiparameter approachG ERG-2004,f or CO 2 and CO 2 mixtures (i.e., CO 2 with CH 4 ,N 2 ,a nd O 2 ).…”

Net, excess and absolute adsorption in mixed gas adsorption

“…4, there are regions where one can find a solution, which is not unique as pointed out by Furmaniak et al (2015). The net adsorption framework will yield one feasible solution in a mixture for positive reduced grand potentials up to the maximum corresponding to the more weakly adsorbed component.…”

“…Recently Furmaniak et al (2015) pointed out the fact that Talu's approach leads to a reduced grand potential that has a maximum above a certain pressure. This can be understood considering the fact that once the net adsorbed amount becomes negative the integral equation, Eq.…”