Synthesis Of AEL Zeolites In Ionic Liquids

SAPO-11 molecular sieve with AEL structure has been widely used in adsorption,separation,catalysis,isomerization reaction and other fields due to their unique pore structure and suitable acidity.The change of morphology is closely related to their specific surface area,strong/weak acidic site ratio,mesoporous/microporous number,number of active sites and so on.Therefore,morphology regulation of SAPO-11 molecular sieve crystals is of great significance for their application performance.Since the scientific community put forward the concept of"green chemistry",people have paid more and more attention to the problem of environmental protection and energy saving in the chemical industry.As a new,efficient and green synthesis process,ionothermal synthesis has great space for development in the field of molecular sieves synthesis and application.The study of ionothermal synthesis of aluminosilicate molecular sieve is very limited,and the regulation of molecular sieves morphology is less.Therefore,on the basis of ionothermal synthesis SAPO-11 molecular sieves,this paper systematically studies the influence of various synthetic factors on the morphology and properties of SAPO-11 molecular sieves,and explores the synthesis mechanism of AEL molecular sieves in ionic liquids.This paper first synthesizes SAPO-11 molecular sieve in 1-ethyl-3-methylimidazole chloride（[EMIm]Cl）,then the crystallization temperature,crystallization time,phosphoric acid content,ionic liquid content,silicon content is regulated,the effects of these factors on the synthesis and morphology of molecular sieves is studied.The optimum synthesis conditions for SAPO-11 molecular sieve is determined as follows:the molar ratio of materials is:15IL:1Al₂O₃:2P₂O₅:0.2HF:0.1SiO₂,the crystallization temperature is 200℃,and the crystallization time is 24h.After that,it studies the structure guidance of ionic liquids by changing the types of ionic liquids and exploring the influence of the change of ionic liquids on the synthesis SAPO-11 in different synthesis systems,SAPO-11 molecular sieve is successfully synthesized in[EMIm]Cl,1-ethyl-3-methylimidazole bromide（[EMIm]Br）,1-butyl-3-methylimidazole chloride（[BMIm]Cl）.It finds that the anions determine their thermal stability.In the synthetic environment with higher stability（[EMIm]Br system）,the crystals can nucleate and grow rapidly,the size of the sample is larger,and the crystallinity is higher.Cations are related to the charge density of the synthetic system.When the cation is a two-substituted short carbon chain,the charge density is larger and the interaction of the molecular sieves skeleton is stronger,the structure guidance is stronger,it can produce more stable molecular sieve products.To investigate the effect of crystallization on the synthesis and morphology of molecular sieves,microwave crystallization technology is introduced to find that microwave crystallization can greatly shorten the crystallization time,increase the crystallization rate,and reduce the sample size significantly.And synthesizes nano-sized SAPO-11 in[EMIm]Cl,significantly increased the specific surface area and mesoporous volume,and finally formed hierarchical porous SAPO-11 molecular sieve.Lastly,metal heteroatom（Fe,Cu,Co,Zn）is introduced into the ionothermal synthesis aluminum phosphate molecular sieve to synthesize the Me APO-11molecular sieve with AEL structure,and the structure guidance of heteroatom is explored.It finds that the type and content of metal heteroatom can affect the morphology,structure and acid properties of the molecular sieves.It finds that the morphology of the sample by ionothermal synthesis is greatly changed comparing with the traditional hydrothermal synthesis,and the ratio of strong/weak acid content changed obviously.