Synthesis Of Silicalite-1Zeolite Membrane And Its Application In Separation Of Ethanol From Water

Silicalite-1membrane is a hydrophobic membrane with all-silica structure. It has strong adsorption and transportation property to ethanol over water. Silicalite-1membrane has great power to bring tranditional fermentation techonology to be trending towards serialization and industrialization. Here is the destination that we were doing researches about Silicalite-1membrane.Researching the synthesis condition of each size of Silicalite-1seeds in microwave oven was put to the first step in this work. Then we used different sizes of seeds to prepare hierarchically-sized seed layer which could lead to highly-compact and c-oriented Silicalite-1membrane. This membrane has good separation performance in separation of ethanol from water and has excellent repeability which gave it potential to be applicated in other process of zeolite membrane preparation.1. In order to achieve the assumption of hierarchically-sized seed layer, we had explrated the synthesis condition of each size of Silicalite-1seeds in microwave, and each size of silicalite-1seeds between0.1and3μm could be prepared by certain condition. These work shows that with the synthesis temperature getting higher, with the synthesis time getting longer and the water content getting more, silicalite-1zeolites would getting bigger. Microwave condition favors the growth rate of silicalite-1zeolites which also show coffin-shaped. When fluoride ion was adding, the same size silicalite-1zeolites would correspond to different synthesis condition, and each size of silicalite-1seeds between0.25and7μm could be prepared in another series of synthesis conditions. These work shows that when fluoride ions were adding, it can’t synthesize silicalite-1zeolites in microwave oven, and normal oven would give the twinning structure to F-silicalite-1zeolites in normal oven. This twinning structure appears that two small single crystal twinning to two sides of b-axis of one big single crystal.2. An excellent seed layer can evolve to high-quality zeolite membrane. With regard to this, we have proposed an assumption of hierarchically-sized seed layer and put it in reality on mullite tube first. With this kind of seed layer we prepared a a series of highly-compact Silicalite-1membrane. XRD patterns have showed that these membranes are typically c-oriented with highly twinning structure. Using these membrane to the separation of5% ethanol/water under60℃, the highest separation factor can be53.1with flux of2.93kg/(m2h). Also, the relative standard deviation (RSD) of separation factor,4.7%, was showing high repeability.3. We have also tested the applicability of hierarchically-sized seed layer on (α-Al2O3tube, which shows the same morphology with the one on mullite tube. In The same separation system, it presents a little lower flux and separation factor, but still high repeability.4. Inner-outer synthesis mode was also investigated in this paper. When it comes to use this membrane in the same pervaporation system, the separation factor was also as high as the membrane synthesized in outer synthesis mode, but with varied flux, such as higher than3kg/(m2h) or lower than2kg/(m2h). However, it indicated that higher performance could be expected.