1. Introduction
In recent years microporous materials have attracted considerable attention because of their characteristics features as molecular sieving materials. The use of microporous materials to make membranes for molecular sieve applications such as gas separation is an ever-growing area of research [1]. Over the last decade, microporous silica membranes have been considered to be promis- ing materials for clean-energy systems since they can separate small molecules from gas mixtures based on their different kinetic diameter [2]. Due to the microporous nature of the silica network, silica membranes allow the permeation of small gas molecules such as H2. Hence, silica membranes with high flux of H2 as well as high selectivity of H2 over others gasses such as CO2, N2 and CH4 have been prepared by sol–gel method and dip-coating [3,4]. Sol–gel technique is a simple and effective way for the synthesis of microporous silica membranes. Therefore, from economical point of view, molecular sieve silica membranes are becoming very competitive against traditional non-hydrostable and expensive metal membranes such as palladium and its alloys.