Preparation Of NaA Zeolite Membrane And Its Application

Zeolite NaA has a pore structure of eight-membered ring,small pore size of 0.42nm,and it's extremely hydrophilic.Thus it exhibits a good separation of organic matter in pervaporation dehydration,especially for ethanol and isopropanol solution.In addition,zeolite NaA membranes have the advantages of good chemical stability,thermal stability and strong mechanical strength.However,because of the high cost and the method of preparation needs to be improved,the zeolite NaA membranes have not been widely used for industrial application until now.Therefore,the key to the application of membrane in large-scale industrial production is to reduce the cost and find a better preparation method.Most of the secondary growth method and vapor-phase transformation method have been reported.The secondary growth method is influenced by seed crystal,the uniform particle size and high purity crystal preparation process is more complex,this method is widely used in the laboratory,but is not conducive to enlarge the production;because There is amorphous gel phase to use,the membrane prepared by vapor-phase transformation is easily lead to cracks the needle hole.Therefore,in order to prepare a continuous and dense NaA zeolite membrane with high separation performance,this paper proposes an improved method of in-situ hydrothermal preparation of NaA zeolite membrane on the outer surface of tubular?-Al₂O₃,it can solve the problem of nutrient supply shortage effectively.The prepared membranes were characterized by XRD and SEM,and the pervaporation performance of the prepared membranes was evaluated and compared via pervaporation device.The main contents and conclusions are as follows:?1?The improvement of in-situ hydrothermal synthesisThe effect of synthesis conditions on the properties of zeolite NaA membrane was studied from two aspects:promoting crystal growth and increasing the number of nuclei.By the carrier tube and the synthetic solution are aged together,so as to achieve the aim of increasing number of crystal nucleus.Increase the density of nucleation sites,but the prepared zeolite NaA membrane is discontinuous.The C₂H₅OH/H₂O separation factor is15.96,permeation flux is 2.593mol/?h·m²?;By updating synthetic solution during the crystallization process provides fresh crystal nucleus and nutrition,so as to achieve the aim of promoting crystal growth,the prepared zeolite NaA membrane is breakup,the C₂H₅OH/H₂O separation factor is 15.53,permeation flux is 2.617mol/?h·m²?;by rotating crystallization method to improve the supply of membrane nutrition,the prepared zeolite NaA membrane is mixed and discontinuous,the C₂H₅OH/H₂O separation factor is 13.61,and the permeation flux is 2.262mol/?h·m²?;carrier before aging preset and update the synthesis of liquid used at the same time to modified in-situ hydrothermal method,continuous density of NaA zeolite membrane was prepared,the improved hydrothermal preparation of zeolite NaA membrane's C₂H₅OH/H₂O separation factor is 20.2,permeation flux is 2.596mol/?h·m²?.?2?Zeolite NaA membrane permeates vaporized dehydration in organic solventsWe also have applied the prepared NaA membrane on the?-Al₂O₃ carrier for the dehydration of ethanol,isopropyl alcohol,acetone and pyridine.Results show that a ethanol solution with high purity of 99.21 wt.%can be obtained from the output,when the feedstock is a 89 wt.%ethanol solution,the feed temperature is 75?,and the treatment capacity is 8600mL/?h·m²?;That a acetone solution with high purity of 99.21wt.%can be obtained from the 95wt.%acetone solution,the feed temperature is 54?,and the treatment capacity is 3440mL/?h·m²?;The isopropanol solution with high purity of 99.37wt.%can be obtained from the 95wt.%isopropanol solution,the feed temperature is 80?,and the treatment capacity is 6880mL/?h·m²?;The pyridine solution with high purity of 99.61wt.%can be obtained from the output,when the feedstock is a 95wt.%pyridine solution,the feed temperature is 96?,and the treatment capacity is 1720mL/?h·m²?.