Mass transport in zeolite membranes for gas treatment: a new insight

This chapter represents an insight of a novel approach concerning modelling and characterization of the mass transport of light gases (e.g., CO2, H2, CH4, CO) in zeolite membranes, like silicalite and NaY. In particular, Knudsen and surface diffusion are paired to each other by the adsorption loading, which interestingly implies the presence of the blocking effect of the Knudsen flow, reduced at low temperature and high pressure because of the adsorbed molecules. It is shown how the necessary adsorption parameters, like heat of adsorption and saturation loading, are evaluated from adsorption isotherms as a function of temperature using a systematic methodology accounting for the weaker interaction of the molecules with increasing temperature. This methodology allows permeance and selectivity to be evaluated, providing a way to predict with efficacy the membrane behaviour in a wide range of temperature and pressure under mixture condition, allowing to identify the optimal working conditions.