Supported MFI Zeolite Membranes for Water Treatment

Intense research efforts are being dedicated to the development of zeolitic membranes in different separation processes when polymeric membranes cannot be utilized owing to the high operating temperature and the presence of aggressive solvents [1]. Different preparation techniques have been developed to obtain almost defect free zeolite membranes. Nowadays, despite these efforts, the industrial applications are only represented by LTA and T membranes for organic solvent dehydration [2]. The most used method is the secondary growth. It decoupling zeolite nucleation from crystal growth allows the optimization the operating conditions of each step independently. It presents two steps: seeding and growth. Seeding is a very crucial step. More controllable seeding procedures involve the filtration of a zeolite water slurry through a porous support. However, coverage uniformity problems can happen using tubular supports. This problem can be overcame using a seeding where the filtration is combined with the rotation and tilting of the support [3]. In this work MFI zeolite membranes on tubular alumina supports were prepared by secondary growth method, using the new cross-flow seeding procedure. The influence of different seeding parameters on the membrane quality was investigated to improve the membrane quality. Morphology of the zeolite layer and crystals topology were observed by scanning electron microscopy and X-ray diffractometry, respectively. The prepared membranes were also characterized in gas and liquid phases by permeation tests.