(208d) Calculation of the Isosteric Enthalpy of Adsorption in Monte Carlo Molecular Simulation: New Equations Addressing Bulk Phase Nonideality and Isosteres of Total Adsorption
In the present work, we reexamine equations for the IEA in light of recent work [5-8] that stresses the importance of analyzing absolute adsorption isotherms during isostere analysis, and accordingly present new fluctuation-based expressions for the IEA for both single- and multi-component adsorption. These expressions account for non-ideality of both the adsorbed and bulk gas phases, regardless of the gas composition. Using flat-histogram sampling in Monte Carlo molecular simulation , we apply these equations to both single- and multi-component gas adsorption to show how TMMC can yield the IEA for an entire isotherm from statistics collected in a single simulation. We also demonstrate that these calculations compare favorably with isostere-based calculations from either the simple Clapeyron equation or the Clausius-Clapeyron, depending departure from ideality in the bulk gas phase. Additionally, we present sample calculations that highlight the differences between the various definitions of the IEA and discuss when these differences may prove critically important. Overall, we aim to place simulation-based IEA calculations on a firmer foundation so that this important thermodynamic quantity may be used more confidently for the design and analysis of adsorption processes.
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