Crystal Morphology Of AEL Structure Molecular Sieves By Microwave Irradiation And Research Of Isomorphous Substitution

AlPO₄-11 molecular sieve consists of 10-membered ring channels with elliptical pore, which has excellent thermal stability and hydrothermal stability. After isomorphous substitution, these materials with adjustable acidity and catalytic active centers have been widely used in catalysis, petrochemical technology and biological engineering, etc. The present works were applied to synthesize AlPO4-11 molecular sieves with high crystallinity using traditional hydrothermal method. And the synthesized condition was investigated on the basis of previous work. Meanwhile, the effect of the synthesized condition on crystals morphology and crystallization process was systematic investigated by microwave method. After synthesized SAPO-11 and ZAPO-11 molecular sieves by direct crystallization, AEL structure molecular sieves with high content of anisotropic atoms were also syntheisized by microwave secondary method. And the products were characterized by XRD, SEM and FT-IR.1. By adjusting the usage of templates, crystallization time and use of HF, AlPO4-11 molecular sieves with high crystallinity were synthesized by traditional hydrothermal method using diisopropylamine as templates. Through adjusting the crystallization time, the result of XRD and SEM was investigated together after adding HF into the synthesized system. It showed that HF shortened the induced period of AlPO4-11 molecular sieves crystallization while the crystals grew slowly to big clump.2. By investigating the effect of synthesized pressure, the optimal synthesized pressure was fixed at 400 kPa. After ageing, it is found that ageing process leaded to the change of crystallization process, therefore, molecular sieves with different morphologies were obtained.3. When the reactant molar ratio was fixed at n(Al₂O₃): n(P₂O₅): n(DIPA): n(H₂O)=1: 1.25 : 1 : 100, AlPO₄-11 molecular sieves aggregated to spheric morphology in the microwave system under 400 kPa for 6 h. After adding some cetylpyridinium chloride, the spheric aggregates were improved to get sleek surface. It is found that the morphologies of AlPO₄-11 aggregates changed from sphere to clump then to faggot by extending the crystallization time.4. Rod-like AlPO₄-11 molecular sieves were synthesized by microwave method after adding some HF. With increasing the usage of HF, XRD diffraction intensity of lattice planes(200)and(002)changed to contrary, which was consisted with the crystal morphology changes to get perfect rod-like crystals. The effect of fluorin ions on the crystallization process and crystal morphology was also discussed by increasing the usage of H₂O, the substitution HCl to HF and adding HF in the second synthesis.5. For the crystallization mechanism of AlPO₄-11 molecular sieves in the microwave environment, it is found that AlPO₄-11 molecular sieves were transformed from the hexagonal berlinite crystals after a period of crystallization.6. Rod-like SAPO-11 and ZAPO-11 molecular sieves without any aggregation were synthesized by direct crystallization using microwave technology.7. Rod-like SAPO-11 and ZAPO-11 molecular sieves with high content of anisotropic atoms were synthesized by microwave secondary method. At the same time, the effect of the HF usage and different zince source on the product's crystal phase and crystallinity was also investigated.8. By compared with traditional hydrothermal secondary method, it is found that the main factor to accelerate the isomorphous substitution of anisotropic atoms was microwave effect in the microwave secondary synthesis.9. The composition of elements and acidic centers on the surface of SAPO-11 and ZAPO-11 molecular sieves synthesized by direct crystallization and microwave secondary method were characterized. The microwave secondary method might bring more anisotropic atoms to the surface of molecular sieves to produce more acidic centers compared with direct crystallization.