Thermodynamic study of the linde sieve 5A + methane system

Abstract

The heat capacity from 50 to 300 K of the empty sieve and of samples containing 0.893, 1.808 and 4.099 methane molecules per cavity are reported. A large “hump” with its maximum near 200 K is found in the plot of the contribution of the sorbate against temperature for all three sorption systems. Adsorption isotherms have been measured over the range 194 to 300 K, and from these the isosteric heat of sorption has been calculated.

A statistical mechanical theory for point particles sorbed in the α-cavities of Linde Sieve 5A has been examined for the case in which the sorbate–sorbate interactions and the interactions between each sorbate molecule and an element of the cage wall are of the Lennard-Jones 6–12 type. In the course of the treatment the sorbate-wall interactions are approximated by a potential derived from the Lennard-Jones and Devonshire cell model. For the evaluation a coupling parameter modification of the usual Monte Carlo procedure has been developed, which should prove useful in other adsorption studies. Fairly good agreement with the results for methane as sorbate are obtained for the isotherms and for the isosteric heats, but not for the heat capacities.