EQUILIBRIUM PARTITIONING OF A DIMERIZING FLUID THROUGH A MICROPOROUS SOLID - A MONTE-CARLO STUDY OF THE DENSITY DISTRIBUTIONS AND ADSORPTION-ISOTHERMS

We have considered a simple, hard-core-type model for an inhomogeneous system consisting of a dimerizing fluid and a microporous solid membr ane with a slit shape, The system is confined to a wide slitlike pore, The bulk and porous regions are in thermodynamic equilibrium. Monte C arlo canonical simulation results are presented for the density distri butions of the particles in the bulk fluid region, in layers close to the outer surfaces of the porous solid and inside the crystalline memb rane, We have observed that dimers prefer to be located in the interst ices of the membrane channels rather than in the membrane cavities. Th e pressure is obtained from the density profiles on the walls of a wid e pore. We show that the adsorption isotherms and the partition coeffi cients are sensitive to the association energy between fluid particles . For almost all densities, the partition coefficient of the monomers is found to be higher than for those particles that belong to dimers. This reflects the shape selectivity of the membrane with respect to th e fluid species during adsorption.