PARTICLE DISTRIBUTION IN A MICROPOROUS MATERIAL

Equilibria in zeolites and other microporous materials are discussed. We present an independent particles in a box approach, which leads to a thermodynamic description of internal occupation equilibria of the type ZXi-1 + ZXi+1 ⇄ 2ZXi, where Z denotes the framework of the material and X the particles that can interchange places. The independent particles in a box are defined by considering a crystal consisting of a finite number of unit cells or boxes each of which can be filled with a specific number of particles. All empty sites in a box have equal probability to be occupied, independent of the number of particles present, as long as sites are available. Each time a particle does fall in a box, the probability for a next one to hit this box is reduced by 1 divided by the number of sites available in an empty box. Hence, as soon as a box is filled, the probability for a particle to hit it becomes zero. The maximum number of particles in the system is equal to the maximum number of sites in a box multipli...