Study Of Silicon Molecular Sieve Membrane Used For Enriching Oxygen

Microporous inorganic membranes (rp0~~<1nm) have great potential for gas separation because of not only its good stability towards higher temperature and corrosive atmosphere but also its molecular sieve property. Typical molecular sieve microporous membranes are carbon-based (CMS) and silica-based structure (Si-MS). Because of the carbon-based structure, the CMS membranes are not suitable for hot oxygen environment, but Silica-based molecular sieve membranes can overcome the drawback and show an even higher selectivity and permeability. So, the investigators have paid more attention to the Si-MS . There are three typical methods to produce silicon-based membranes. They are sol-gel process ,CVD method and pyrolysis method .Comparing with the conventional membranes prepared by sol-gel and CVD methods, separation factors of pyrolysis membranes are much higher. In most cases, permeability of pyrolysis membranes are 10 times higher than the sol-gel and CVD membranes while the separation factors 1-3 times of the conventional membranes. Commonly, if you want to fabricate a pyrolysis Si-MS membrane, the precursor with stereo structure is made first, then the precursor is pyrolyzed, dehydrogenated and decarbonized in an activate atmosphere at high temperature, and finally the skeleton structure which main composition is S1Ox in final product is formed The gaps of the skeleton structure which constitute the pores of the resultant membranes are restricted to a rather lower level. An important reason is that the precursors of these membranes are polymerized by defunctional monomer. It means that the skeletons are composed of irregular arranged macromolecular chains and thus the gaps of the skeletons have random sizes, or, in other words, the pore sizes have a wilder distribution. In this work, we find a feasible way to meet our requirements. Firstly, a silicon resin material with regular molecular arrangement is polymerized by stereospecific polymerization process. Then a silicon molecular sieve membrane with much better permeability and permselectivity is made by pyrolyzing the polymeric resin. The high rate of terminal product which is as high as 80 90% is achieved by adopting the preparation technology that have been developed completely. At last an apparatus used for enriching oxygen is made from the membrane. Its working effect is remarkable, for example, the content of oxygen is 41% and the flux is 18.62l1m2d under the pressure of 0.3 Mpa. Furthermore, the preparation process of the membrane is simple, inexpensive and highly reproducible.