Preparation Of MCM-22 And ZSM-5 Zeolite Membranes On Tubular Porous Ceramic Supports

Compared to organic membranes or other inorganic membranes,zeolite membranes have a variety of advantages,including:good resistance to high temperature,high pressure and chemical corrosion such as acid and alkali,excellent mechanical stability,molecular size level and uniform pore size,exchangeable pores intra-channel cations,tunable framework silica-alumina ratio,and T-site atoms?Si,Al?that can be replaced with other atoms.Therefore,zeolite membranes have a wide range of important applications in the fields of adsorption and separation,catalytic membrane reactors,and sensors.How to prepare dense and high-permeation flux zeolite membranes has always been a difficult and hot topic.In this experiment,MCM-22 and ZSM-5 zeolite membranes were prepared on the inner wall of ceramic tubes.The MCM-22 and ZSM-5 molecular sieves have better stability and wider application range than the A-type zeolite membranes that are currently reported in the research.In the research work of this thesis,the conditions for the synthesis of zeolite membranes were screened and optimized,and the permeation and separation performance of the zeolite membranes for gas separation was investigated.The main research contents and results are as follows:?1?Synthesis and properties of MCM-22 zeolite membrane on theinner surface of tubular alumina ceramic tubes.First,MCM-22 crystals and ITQ-2 zeolite crystals were synthesized and used as seed crystals in molecular sieve membrane secondary growth method and carrier surface modifier before synthesis of zeolite membrane.The effects of various synthesis conditions on the synthesis of zeolite membranes were investigated in detail,including:water content,alkalinity and silica-alumina ratio of the synthesis system,and crystallization time,ITQ-2 modification times,and optimized synthesis conditions were obtained.The structure and morphology of the synthesized MCM-22 zeolite membrane were characterized and its gas permeation separation performance was tested.The results showed that the molar ratio of synthetic fluid components for 0.5HMI:0.075Na₂O:1.OSiO₂:0.033Al₂O₃:54H₂O,96 hours synthesized under the condition of 150?,the temperature of 550? was calcined at a rate of 0.5?/min for 5 hours to obtain the best performance of zeolite membranes.The lamellar structure of MCM-22 zeolite precursor was stripped,and ITQ-2 molecular sieve with MCM-22 zeolite and large specific surface area was obtained.The MCM-22 zeolite membrane was synthesized using an ITQ-2 zeolite modified support.The results of XRD and SEM show that uniform and dense zeolite films are synthesized on alumina ceramic tubes.The thickness of the synthesized MCM-22 zeolite membrane is 17.32?m,and the selectivity is 3.65 for H₂/N₂,indicating that the synthesized zeolite membrane has a certain gas separation capability.while the permeability of gas is H₂,which is 1.09×10^-6 mol·s^-1·m^-2·Pa^-1,and N₂ is 2.98×10^-7 mol·s^-1·m^-2·Pa^-1.?2?Synthesis and properties of ZSM-5 zeolite membrane on theinner surface of tubular alumina ceramic tubes.The ZSM-5 zeolite membranes were synthesized on kaolin-free tubular ceramic alumina supports modified with kaolin and kaolin.The effects of the silica-alumina ratio,the water content,the amount of templating agent,and the synthesis time of the synthetic system were examined in detail,and the optimized synthesis conditions were obtained.The structure and morphology of the as-synthesized ZSM-5 zeolite membrane were characterized,and its gas permeation separation performance was tested.That is,when the molar ratio of each components in the synthetic liquid is 0.8TPAOH:5TEOS:500H₂O:4NaOH:0.015NaAlO₂,the temperature is 180?,the synthesis is 12 hours,and the calcination is carried out at a rate of 0.5?/min for 8 hours at 550?,XRD and SEM results show that the synthesized film has a good appearance.Subsequently,in order to reduce the defects of the synthetic membrane and increase the permeation selectivity of the zeolite membrane,the support was further modified by kaolin which rich in silica-aluminum components.The single-component gas permeation of the zeolite membrane synthesized on the modified layer by the modified method showed that the selectivity to H₂/N₂ is 4.15,and the gas permeability at this time is H₂ of 1.36×10^-6 mol·s^-1·m^-2·Pa^-1,N₂ is 3.28×10^-7 mol·s^-1·m^-2·Pa^-1.