Isotherms isosteres constructed from

We have examined whether a simple non-bonded potential can be developed to be (i) transferable from one zeolite to another and (ii) to simulate without parameter adjustment isosteric heats at different temperatures and sorption uptake isotherms. The sorption of methane into Na- and K- zeolite X, and Na-and K-clinoptilolites was considered. Models for Na-X and K-X were constructed based on the averaged crystallographic results. The non-bonded parameters in a Lennard-Jones potential were iteratively adjusted so as to best reproduce the experimental isosteric heats in Na-X and K-X over a small temperature range. Methane-methane interaction parameters were taken from earlier work [89] and a final iteration was made so as to better fit the experimental sorption isotherms in clinoptilolite. This single and simple non-bonded potential parameter set then reproduces to a reasonable degree... 

A set of such isotherms is shown in Fig. 9 for the system ethylbenzene/ H-ZSM-5. From such sets, in turn, isosteres were constructed and isosteric heats of adsorption, Qiso, determined via the Clausius-Clapeyron equation. This is illustrated in Fig. 10 using the system ethylbenzene/H-ZSM-5 as an example. 

The bands at 1595 and 1443 cm are very close to those observed with the slightly acidic samples Nos. 5 and 6 (see Table 1). They were easily removed by short purging with helium or evacuation. From sets of spectra analogous to those of Fig. 12 (reversible) uptake curves were obtained similar to those of Fig. 8, and likewise isotherms (see, e.g.. Fig. 14) and isosteres (Fig. 15) were constructed therefrom. 

An adsorption isotherm is the relationship at constant temperature between the partial pressure of the adsorbate and the amount adsorbed at equilibrium. Similarly an adsorption isobar expresses the functional relationship between the amount adsorbed and the temperature at constant pressure, and an adsorption isostere relates the equilibrium pressure of the gaseous adsorbate to the temperature of the system for a constant amount of adsorbed phase. Usually it is easiest from an experimental viewpoint to determine isotherms. The coordinates of pressure at the different temperatures for a fixed amount adsorbed can then be interpolated to construct a set of isosteres, and similarly to obtain an isobaric series. 

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