Preparation and High Permeance of SiO2-Modified Substrate Supported ZSM-5 Membrane by Pre-Seeding and Secondary Nucleation

SiO2-modified substrate supported compact ZSM-5 membranes with high permeance were prepared using the secondary nucleation method. The synthesis mixture had a molar composition of 10Na(2)O:84SiO(2): 100NaCl:5TPABr:3500H(2)O. In order to obtain high permeance, a SiO2 meso-porous top layer was added to the macroporous substrate in this study. The SEM images of the seed layer indicate that about 400-500 nm round shaped seeds consisting of 60 nm zeolites fully covered the modifying substrate. The XRD patterns of the zeolite membranes show the purity of the ZSM-5 crystal phase, and reveal the formation of a random orientation on the SiO2-modified substrate. The SEM images of the zeolite membranes indicate that the membranes consist of highly intergrown crystals, with a maximum thickness of about 30 mu m. The results of gas permeability studies indicate that the SiO2-modified substrate supported ZSM-5 membranes show good permeance, with the maximum H-2 permeance achieved being 12.5 x 10(-7) mol S-1 m(-2) p(-1). The maximum H-2/N-2 and H-2/CO permselectivities were 4.01 and 4.37 respectively, which are higher than those of the corresponding Knudsen diffusion. The method used resulted in high permeance, while keeping the sustainable permselectivity, and is therefore desirable for practical applications.