Factors Affecting The Structure-Directing Effect Of Methylamine And Ethylenediamine In The Synthesis Of Open-Framework Aluminophosphates

Zeolites are widely used in catalysis,adsorption,separation and ion exchange due to the diversity of their framework structures,regular channel structure,excellent surface properties.The synthesis of zeolites and related open-framework aluminophosphates need organic amines.But the structure-directing effect can be affected by so many factors,such as the framework and the amount of the structuredirecting agents,the p H and composition of gel mixture,temperature and time of crystallization,solvent polarity and so on.It is so difficult that useing the structuredirecting effect to directly synthesize the aluminum phosphate compound with the target structure.Therefore,it is very important to clarify the mechanism of structuredirecting.In this dissertation,we investigated two synthesis of open-framework aluminophosphates with fine tuning of organic amine structure,we investigated the factors affecting the structure-directing effect of amine.The main results are summarized as follows:1.The influence of environment change around N-atom on the structure-directing effect of organic amine(MA/DMA)in the synthesis of open-framework aluminophosphates was investigagted.By heating the initial gel with the molar composition of n(Al2O3): n(P2O5): n R(MA/DMA): n(H2O)=1 : 1 : 1 : 277 at 200°C,aluminophosphate molecular of Al PO4-53 and Al PO4-21 were obtained,respectively.Protonated methylamine and dimethylamine were located in the framework of Al PO4-53 and Al PO4-21 to balance the negative charge of the framework,respectively.The crystallization processes were investigated by X-ray diffraction(XRD),elemental analysis(ICP)and p H measurement.The difference of the crystallization process and the calculation of the theoretical data indicated that a charge matching between the formal charge density of organic amines and the framework charge density was observed.Furthermore,the difference in the structure of organic amines leads to the charge change around N atom.Then the crystallization process and the liquid phase composition and p H was changed and the final crystal structure was changed.2.The influence of length of carbon-chain on the structure-directing effect of organic amine(EDA/1,3-DAP)in the synthesis of open-framework aluminophosphates was investigagted.By heating the initial gel with the molar composition of n(Al2O3): n(P2O5): n R(EDA/1,3-DAP): n(H2O)=1 : 1 : 1 : 277 at 180°C,aluminophosphate molecular of Al PO4-12 and Ui O-26 were obtained,respectively.Diprotonated ethylenediamine and 1,3-propanediamine were located in the framework of Al PO4-12 and Ui O-26 to balance the negative charge of the framework,respectively.The crystallization processes were investigated by X-ray diffraction(XRD),elemental analysis(ICP)and p H measurement.By comparing the crystallization process and the calculation of the theoretical data,we got some results.These results indicated that the length of the carbon-chain change around N atom of organic amines can affect the amount of charge and the charge density on it,which accordingly affects its structuredirecting ability.Then the Al PO4-12 was changed to the Ui O-26 with a small charge density.