The Synthesis Research Of Aluminophosphate Molecular Sieves Via Efficient Green Method

Due to its porosity and high specific area,molecular sieve is widely applied in the field of adsorption,catalysis and ion exchange.Aluminophosphate molecular sieve,as the third generation zeotype material,is a prominent one among the zeotype family,which have received tremendous interest in its synthesis,characterization and catalytic performance.Compared with hydrothermal and solvothermal synthesis,ionothermal and solvent-free synthesis are two new methods in the reaction system.These two methods exhibit many advantages,such as high yield,low waste emission,and energy-saving,which can provide a green and sustainable approach for the preparation of zeolite.In this work,sorts of aluminophosphate molecular sieves,with high crystallinity,regular morphology and hierarchical pores,have been synthesized by the ionothermal and solvent-free method.The main research contents are as follows:An LTA topology Aluminophosphate molecular sieve was high efficiently synthesized by an improved ionothermal method from a gel containing low-dosage ionic liquids and structure-directing agent(SDA).The influences of organic amine type,crystallization temperature,the molar ratio of ILs/Al2O3,the molar ratio of Amine/Al2O3,and seed crystals on the synthesis of LTA-type material were investigated in detail,to refine the synthetic conditions.The resultant LTA molecular sieves were characterized by XRD,SEM,TG-DTA,CHN elemental analysis,solution 13 C NMR,EDX and N2 physisorption.The results indicate that LTA-type molecular sieve is synthesized even by adding a small amount of seed crystal into initial gels,of which both molar ratios of ILs/Al2O3 and Amine/Al2O3 are decreased to 0.67.Utilization rate of inorganic raw materials during as-synthesis is up to 86% under the optimal conditions.It is the cooperative structure-directing effect between morpholine and 1-ethyl-3-methylimidazolium cations that guides the formation of LTA molecular sieve.The high zeolite yield,as well as high specific surface area,is obtained from this method after calcination.It is also a hierarchically porous material with both micropores and mesopores inside.AlPO4-11 with AEL topology has been successfully synthesized under solvent-free conditions.The key influential factors controlling the crystallization of AFI structure,such as,HF/Al2O3 and DIPA/Al2O3 molar ratio,and the milling were thoroughly investigated.The resultant AEL molecular sieves were characterized by XRD,SEM,TG-DTA,CHN element analysis and N2 physisorption.The results indicate that the addition of seed crystals exhibits little effect or even negative effect on the phase purityand crystallinity of the products.On the contrary that mechanochemical pretreatment can not only affect the morphology of AEL zeolite,but also,more importantly,can improve the phase purity and reduce the consumption of structure-directing agent.Moreover,the mechanochemical pretreatment and its combination with seed crystals can be used as two powerful tools to increase the mesopore volume and yields of AEL zeolite.