Permporometry Characterization Of Pore And Defect Size Distribution For Supported Zeolite Membranes

As alumino-silicalite crystalline materials, zeolite membranes have regularly controllable pores of molecular dimensions. A defect-free zeolite membrane is monocrystalline or polycrystalline film, which consist of molecular sieve pores and with no defects such as cracks, pinhole or grain boundary defect. Molecular sieve separation mechanism is the foundation of gas separation, and this is also the goal of molecular sieve membrane development. So far, however, due to the intrinsic qualities of zeolite molecular sieve membrane and the imperfect on the synthetic technology, defects always form inevitably, which limit the large-scale industrial application of molecular sieve membrane, therefore, molecular sieve membrane defects become one of the main limit for realizing industrialization. Hence, how to eliminate disadvantages and improve the method of preparation and template-removal of molecular sieve membranes are very dispensable. Moreover, thin molecular sieve membrane of high-flux, high-selectivity and no-defects is important for their applications in laboratory studies and process industries.Pore size and pore size distribution of molecular sieve membrane is a very important parameter, which have a serious impact on separation performance. Hence, the evaluation of pore size and pore size distribution of the zeolite membrane has very important significance. The measurement of the permeance of a non-condensable gas as a function of the vapor pressure of condensable gas in the feed stream allows the estimation of pore size distribution by permporometry and instrument designed by our laboratory. To obtain the mathematical model for the evaluation of pore size distribution of zeolite membranes, we consider the inverse process of permporometry. The pore of zeolite membrane can be divided into countless intervals and in each interval the permeance of non-condensable gas can be calculated respectively, at last, the pore size distribution of zeolite membrane can be calculated by integral mean value theorem and recursive method.In this paper, permporometry experiment combined with a mathematical model can evaluate pore size distribution of zeolite membranes effectively. As a result, permporometry provide a technological mean to evaluate the completeness and separation performance of zeolite membrane, meanwhile, permporometry also provide an effective guidance for the synthesis of zeolite membrane and the removal of template.