The Zeolite ZSM-5 membrane study; synthesis, permeation and modeling.

Zeolite particles formed in the synthesis solution assume a negative charge due to electrical double layer effects. The membranes synthesized via electrophoretic deposition produce a thin continuous zeolite ZSM-5 layer on the porous alumina substrates. The thickness of membranes can be controlled by varying the precursor concentration, applied potential, and synthesis time. The permeation for a variety of gases through the membranes is examined. The diffusion properties are measured at near ambient temperature and pressure. Selectivity of n-butane over iso-butane is observed on every membrane. The diffusion coefficient of gases on ZSM-5 is also evaluated by gas adsorption on zeolite powders. The results of these studies show an ability to predict the effective diffusion coefficients. The estimation of molar fluxes across the membranes using the Maxwell-Stefan approach predicts a higher flux for thinner membranes. However, the calculations also show that even minor defects in the membrane have a great effect on the permeation rates.