Preparation,Modification And Application Of SAPO-34 Zeolite Membrane

SAPO-34 zeolite has excellent thermal stability,acid resistance stability and unique pore structure.At present,most of the related studies focus on catalysis,adsorption and gas separation,while the research on liquid separation is rarely reported.Therefore,a kind of SAPO-34 zeolite membrane with good liquid separation performance was prepared in this paper,and its modification and application were studied.The specific research contents are as follows:1.SAPO-34 zeolite was prepared by hydrothermal synthesis method as seed crystal,and SAPO-34 zeolite membrane was synthesized on α-Al2O3 hollow fiber support by primary and secondary synthesis,respectively.The crystal morphology of the samples was characterized by scanning electron microscopy(SEM)and X-ray diffractometry(XRD).SAPO-34 zeolite membrane was used to separate organic solution by pervaporation.The influences of synthesis times,Si-Al ratio,operating temperature,type of organic matter and concentration of organic matter in the raw material liquid on the separation performance of zeolite membrane in the pervaporation test were systematically explored,and the stability of SAPO-34 zeolite membrane in the long-term operation of different kinds of raw material liquid was tested.The results show that the crystal shape of SAPO-34 zeolite films prepared by four different Si-Al ratio formulations after hydrothermal synthesis at 150℃ for 48 h was all cube.In addition,SAPO-34 zeolite has a good performance in pervaporation separation of small molecular organic matter solution,and the separation effect can be optimized by adjusting the concentration of organic matter in the feedstock solution and the operating temperature.When the raw material solution was 90 wt.%ethanol-water solution and the operating temperature was 65℃,the separation factor can reach 1782,and the corresponding flux was 0.92 kg/(m2·h).When the raw material solution was 90 wt.%acetic acid-aqueous solution and 90 wt.%isopropanol-aqueous solution,the separation factors can reach 1424 and 1488,respectively,and the corresponding osmotic fluxes were 0.86 kg/(m2·h)and 0.80 kg/(m2·h),respectively.2.SAPO-34 zeolite was modified by adding cobalt nitrate hydrate directly into the synthetic solution.Co-SAPO-34 zeolite films with different metal element cobalt(Co)content were synthesized by the secondary growth method on α-Al2O3 hollow fiber support,respectively.SEM and XRD were used to characterize the microstructure of the modified zeolite membrane.EDS was used to verify the introduction and content of Co.BET was used to measure the specific surface area of the modified zeolite.Co-SAPO-34 zeolite membrane was studied for the separation of organic matter solution by pervaporation and the retention of dye.In the dye interception experiment,the preferred Co-SAPO-34 zeolite membrane synthesized in one time was selected to systematically explore the effects of Co addition,calcination times and dye types on the interception performance of the zeolite membrane,and the stable operation time of the zeolite membrane in the dye was tested.The results showed that:When 500 ppm NaCl or Na2SO4 was added to Congo red solution at the operating temperature of 20℃,the rejection rate of the modified zeolite membrane for Congo red was 95.7%,the rejection rate of NaCl was 15%and that of Na2SO4 was 22%.The corresponding flux was 6.5 L/(m2·h).