Potential Applications of Zeolite Membranes

Zeolite membranes are able to separate continuously mixtures of substances on the basis of differences in molecular size and shape and also on the basis of different adsorption properties. Zeolite membranes are also interesting for the use in membrane reactors due to their thermal and chemical resistance. However, reproducibility problems and high cost hinder their industrial application. The one-step and the secondary growth are the two methods used in the preparation of zeolitic membranes. The secondary growth method, decoupling zeolite nucleation from crystal growth, allows the optimization of the operating conditions for each step. Seeding is a critical step that can influence the membrane’s quality. A new procedure for the seeding crystals was designed and used to achieve the selective zeolitic layer on the inner tubular support surface. The membranes prepared for the secondary growth method coupled with the cross-flow seeding procedure were used in different processes. First of all, Faujasite (FAU) zeolite membranes were used in CO selective oxidation (SelOx) in simulated membrane reactors reformate gas. Another example showed the possibility to use mobile-type five (MFI) membranes for water desalination by means of vacuum membrane distillation process.