Intrapore Synthesis of Silicalite Membranes

Abstract

The zeolitic layer of most supported zeolite membranes lies partially outside of the pores and partially inside the pores of the support. Coronas t al prepared ZSM-5 membranes by two techniques, one resulting in an external layer with little pore infiltration, the other resulting in a patchy external layer and a deep internal layer, the fatter structure having better separation properties. Generally, it has proven difficult to determine which of the two layers is responsible for the separation properties. Intrapore separation layers have the advantage that they can be grown on supports of lesser quality and are not susceptible to crack formation during calcination. In this study intrapore membrane growth was achieved by means of seeding inside the pores of the support. Subsequent growth of the seeds led to pore filling by the zeolite up to a certain depth from the external surface. In a departure from previous ZSM-5 membrane studies, growth of the zeolite layer was carried out at temperatures below 100°C that dispenses with pressure vessels and allows facile stirring and midsynthesis change of solution.

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