Synthesis Of {111} Preferential Oriented NaY Zeolite Membraenes And Preliminary Study On Pervaporation Performance

The unique structural features of NaY-type zeolite membrane, such as high aluminum content of the skeleton and the presence of highly dispersed Na+ around the cage hole give, given it stronger hydrophilic and polar. Those and the large aperture (0.74 nm) and three-dimensional cage-like pore structure of the zeolite make it can be used preperentially in the separation of water/organic, alcohol/organic and benzene/alkane mixtures. The zeolite membranes have drawn much attention by now.In this thesis, for the first time, on a-Al2O3 substrates, the {111} preferentially oriented continuous and compact NaY-type zeolite membranes were prepared by aging synthetic mixture-secondary in situ method and by secondary growth of the EMT-type zeolite seed layers. The EMT-type zeolite seed, seed layers and NaY-type zeolite membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and spectroscopy (EDX). The membranes synthesized were used to separate the methanol/dimethyl carbonate mixture. The details are as following:1. By aging synthetic mixture-secondary in situ method, the NaY-type zeolite membranes were prepared. The effects of aging method, aging time, crystallization temperature and crystallization time on the structure of the membranes obtianed by the first time in situ crystallization were investigated. The results showed that the membranes with stir aging method and aging for 24 h covered the substrates more completely. With the crystallization time of 6 h, the membranes were pure, without the zeolite of P-type. The membranes with the crystallization temperature of 100? were {111} preferentially oriented.2. The NaY zeolite membranes were prepared using the secondary growth method. The EMT seeds were obtained using the template and non-template methods, respectively. The zeolite seed synthesized by crown-16 ether was denoted as A. The crystal grains were about 2-3?m with the crystallization time of 6 d and 10 d. The FAU-type zeolite appeared when the crystallization time was 10 d. So the crystals with 6 d were selected as seeds. The seed synthesized by non-template method was denoted as B. The more appropriate crystallization time was 36 h at temperature of 30?, and the crystal grains were about 20 nm and the SOD type zeolites formed at shorter crystallization time.Seed layer A and seed layer B were prepared by ultrasonic method. When the amount of seeds solution was 0.75 mL (0.2 wt.% seed ethanol solution), both the larger seeds A and the smaller seeds B can not covered the surface of the substrates. When the amount of the seeds solution was 1.0 mL, the two kinds of seed layers covered the substrates surface completely. By secondary growth, the seed layer A grew to be randomly oriented and compact membrane and the seed layer B grew to be {111} preferentially oriented and compact membrane. The membrane from seed layer B was asymmetric, with a seed layer between the top compact membrane and substrate. Both the membranes were about 10?m.3. NaY-type membranes synthesized were used to separate the mixture of methanol/dimethyl carbonate by pervaporation. The membrane growing from seed layer B possess the best pervaporation performance. For the solution of mass ratio 50/50, at 50?, the permeation flux was 7.85 kg m-2 h-1 and the separation factor was 4. The membrane can separate the mixture to some extent but the result was lower that that reported.