| Energy issue is a problem that cannot be ignored in today's society.As a green energy,ethanol is in big demand and is widely used as a liquid fuel alone or mixed with gasoline as fuel,which will help to reduce oil dependence and to save oil resources.Ethanol can be produced by the bio-fermentation process,but the concentration is lower than that of 10wt%due to the inhibition of the product(ethanol),the separation of ethanol from the fermentation system is a key technology in the area of ethanol production and application.Pervaporation as a new kind of separation process has many advantages such as easy operation,low energy consumption and high efficiency and so on.MFI-type(silicalite-1)membrane show strong hydrophobic performance since it molecular sieve contain no aluminum element.It has great potential application to separation of traces organic compounds from aqueous solutions especially in ethanol/water mixture.However,there are still some difficulties in the preparation of the non-defective silicalite-1 membrane and applied in the pervaporation separation of ethanol/water mixed solution.There are several key processing parameters on synthesis of non-defective silicalite-1 zeolite membrane,including the amount of seed crystal,seed size,the molar ratio the of synthetic solution,the crystallization temperature,the synthetic time,the support material and so on.In this paper,the silicalite-1 zeolite membrane was prepared by the secondary growth method using the stainless steel and ?-Al2O3 ceramic as the support and the effect of molar ratio,crystallization time,crystallization temperature,the support material on the properties of membrane were explored by SEM,XRD and EPMA.The separation performances of the silicite-1 membranes for ethanol/water mixture were investigated by the pervaporation experimental setup.(1)The effects of crystallization temperature(T),crystallization time(t),template content(TPAOH/TEOS molar ratio)and water content(H2O/TEOS molar ratio)on the silicite-1 seed appearance of the impact were investigated.The average particle size of seed decreased with the increase of crystallization temperature,crystallization time,template content and synthetic liquid water.When the crystallization temperature was 175 °C,the crystallization time was 8 hours,the molar ratio of TPAOH/TEOS is 0.3 and the synthesis molar ratio of H2O/TEOS is 160,the seed size appearance the uniform size and average particle size is 500nm.(2)The effects of the separation of the ethanol/water on the silicalite-1 zeolite membrane synthesized on the stainless steel and the a-Al2O3 ceramic support were investigated.When the stainless steel as a support,the feed temperature is 60 °C and the concentration is 5wt%,the separation factor was only 4.2,and the total permeation flux is 1.8kg ·m-2· h-1.When the support was ?-Al2O3 and the other conditions were same,the factor was 26,the total permeation flux was 1.48 kg·M-2·h-1.(3)The effects of crystallization temperature(T),crystallization time(t),template content and water content on Silicalite-1 zeolite membranes were investigated.When temperature was 175 °C,the crystallization time was 8 h,the TPAOH/TEOS molar ratio of the synthesis solution was 0.1,the molar ratio of H2O/TEOS was 60,the surface of the prepared zeolite membrane was uniform and continuous,the membrane showed the high separation selectivity to 5wt%Ethanol/water mixture.(4)The effects of temperature and concentration on separation performance for 5 wt%ethanol/water mixture using silicalite-1 zeolite membrane were investigated.When the temperature of the feed ranged in 30-70 °C,the separation factor and the permeation flux increased with the temperature increasing.When the concentration ranged in 5-20 wt%,the permeation flux and the separation factor decreased with the increase of the concentration. |
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