CHAPTER 7. Mass Transport in Zeolite Membranes for Gas Treatment: A New Insight

Abstract

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