The Synthesis Research Of New Aluminophosphate-Based Molecular Sieves Via Co-template Directing Method

Zeolite crystals,as a kind of microporous crystal material with uniform pore structure and pore size,was wildly used in catalysts,adsorbents and ion exchangers.The development,synthesis and characterization of novel aluminophosphate or heteroatom aluminophosphate molecular sieve have attracted much attention.Compared with hydrothermal/solvothermal method,the ionothermal method,solvent-free method and microwave heating method are novel green synthesis routes,which provide a new perspective for realizing green synthesis of molecular sieves.Based on improved ionothermal method and solvent-free method,three kinds of aluminophosphate molecular sieve with-CLO-type,ATN-type and LEV-type were synthesized.The research projects are as follows:Firstly,based on improved ionothermal method,a novel aluminophosphate molecular sieve with-CLO topology was synthesized using low dosage of ionic liquid as solvent and template.The effects of crystallization temperature,time and type of template on the crystal phase of-CLO aluminophosphate molecular sieve were discussed in detail.The product-CLO molecular sieve was characterized by XRD,SEM,N₂ physical adsorption and desorption,TG-DSC,CHN elemental analysis and liquid ¹³C NMR.According to the results,both the ionic liquid and the diisopropylamine are exists in the framework of-CLO,which indicated the ionic liquid and diisopropylamine synergistically guide the synthesis of the-CLO molecular sieve.In addition,it has obvious advantages such as high utilization of inorganic atoms and lower ionic usage,which is in line with the green synthesis concept and beneficial for promoting the development and application of the-CLO molecular sieve material and the ionothermal synthesis method.Secondly,a novel iron-aluminophosphate molecular sieve with ATN-type was synthesized by solvent-free method for the first time.The effects of crystallization time,temperature,Al₂O₃/P₂O₅,Fe₂O₃/Al₂O₃ and the addition amount of template on the synthesis process were studied in detail.The composition and structural characteristics of resultant FeAPO-39molecular sieves were intensively studied by XRD,FT-IR,TG-DTA,CHN elemental analysis,ICP-AES,SEM,TEM,N₂ physisorption,UV/Vis diffuse reflectance spectroscopy and M?ssbauer spectroscopy analyses.The results indicate that DPA molecules may codirect the synthesis of ATN zeolites along with additional structure-directing agent NH₄⁺ions resulting from iron source.Owing to the specific structure-directing role provided by iron source,the synthetic strategy presented in this paper may provide a potential application in the solvent-free synthesis of other aluminophosphate zeolites.At last,iron-containing aluminophosphate molecular sieve with LEV-type?Fe-LEV molecular sieve?has been successfully synthesized via microwave-assisted ionothermal method in low-dosage of eutectic mixture solvent,which is the first example of Fe incorporated aluminophosphates with the LEV-type.The effects of crystallization time,temperature,Al₂O₃/P₂O₅,HF/Al₂O₃,Fe₂O₃/Al₂O₃ and the addition amount of tetraethylammonium bromide on the material were studied in detail.The structure and morphology of representative Fe-LEV sample,as well as the structure directing effect of eutectic mixture were thoroughly analyzed by various techniques including XRD,²⁷Al and ³¹P MAS NMR,ICP-AES,DR UV-Vis,ESR,XPS,N₂ adsorption/desorption,NH₃-TPD,SEM,TEM,EDX,CHN elemental analysis,TG-DTA and FT-IR spectra.It was found that only combined precursor with proper structure-directing agent can yield Fe-LEV molecular sieve,in which choline cations and intact tetraethylammonium bromide molecules were identified to be the structure-directing agents.Most importantly,this method can not only shorten synthesis time,but also synthesize Fe-LEV molecular sieve with high surface area and iron content,as well as hierarchical structure,which means that these zeolite materials have great potential in some industrial applications.