Supported zeolite membrane by vapor-phase regrowth

A new method for preparing slipper-red zeolite membrane is proposed. A layer of colloidal MFI zeolite is deposited on a porous ultrafiltration support, on which a silica barrier layer has been precoated. The composite is then heated at 100 degrees C under saturate water vapor for 30 h to obtain a very thin zeolite membrane with a glassy took. Under SEM, the zeolite membrane exhibits obvious void when the particles deposited were 100 x 150 nm in size. The particles are packed much closer if 80 x 100-nm particles were used. With smaller (60 x 80 nm) particles, the boundary between particles fuses together, and a continuous zeolite membrane could therefore be prepared. The membrane thickness could also be reduced by depositing less colloidal zeolite for regrowth to obtain a continuous zeolite membrane as thin as 0.5 mu m on top of a multilayer porous alumina support. Some preferred orientation of the elliptical zeolite particles is observed on the surface of the membrane but no preferred crystallograph orientation is confirmed. The reproducibility of this preparation method was checked by room temperature permeation measurements of several gases. Nearly identical results were obtained On two separately prepared membranes. Permeation results also confirmed that there were very few, if not free of pinholes in the zeolite membrane so prepared.