Ionothermal Synthesis And Characterization Of Hierarchical AlPO-34 And FeAPO-34 Molecular Sieves

In this paper,the AlPO-34 molecular sieve and FeAPO-34 molecular sieve as the research focus,under the conditions of ionothermal synthesis of these two molecular sieves at atmospheric pressure,the use of XRD,SEM,N2 adsorption test,UV-Vis and many other characterization methods detailed Analyze and apply the two kinds of molecular sieve materials to the heavy metal cation adsorption and phenol hydroxylation reaction in the sewage according to the nature of the molecular sieve itself.The main results obtained in this paper are as follows:(1)The CHA-type molecular sieve AlPO-34 was successfully prepared under ionic heat conditions using 1-butyl-3-methylimidazolium bromide ionic liquid as solvent and structure directing agent.In the reaction system,cyclohexylamine was added as a co-template agent,and the concentration of cyclohexylamine was changed to obtain different crystalline aluminum phosphate molecular sieves,which proved that the amount of organic amine can be played without entering the framework structure under the conditions of ionothermal synthesis.Molecular sieve crystal form regulation.The synthesis system is different from any previous ionothermal synthesis method of AlPO-34,which opens up a new approach for the ionothermal synthesis of AlPO-34.The aging process was introduced into the ionothermal synthesis process.The product was observed by scanning electron microscopy.The product was a spherical structure formed by the agglomeration of a large number of crystal particles.After aging,the crystal size was effectively reduced and a more regular crystal morphology was brought.The nitrogen adsorption test showed obvious hysteresis loop,indicating that it is a multi-level structure with micropores and mesopores.The preparation process of the hierarchical structure avoids the use of mesoporous templates or complex deformed element treatment and realizes the direct synthesis of molecular sieves with a hierarchical structure.The hierarchical AlPO-34 molecular sieve was prepared and used for the adsorption tests of heavy metal cations of Cr,Cu,Zn and Pb.Due to its high specific surface area and uniform mesoporous/microporous structure characteristics,it exhibits excellent adsorption.ability.Among them,when the concentration of heavy metal ions is 200 ppb,the removal rate of Cr(III)ions can reach 95.68%,the removal rate of Zn(II)ions can reach 94.53%,and the removal rate of Pb(II)ions can reach 92.51%.The removal rate of Cu(II)ion is 89.29%,the highest Cr partition coefficient is 2.21×104,Zn and Pb are slightly lower,about 1.73×104 and 1.24×104,respectively;the Cu distribution coefficient is lower,about 8.34×103.(2)Adding Fe source to AlPO-34 ionothermal synthesis gel,meanwhile,reducing the Al source addition to increase the probability of Fe substitution into the "AlO4" tetrahedron,and successfully prepare the high-speed iron under the conditions of ionothermal synthesis.ICP-AES showed that the iron content in the prepared FeAPO-34 molecular sieve was up to 11.62%,and the framework iron was up to 10.68%.Owing to the same ageing process used in the preparation process,the FeAPO-34 produced exhibits a spherical structure with hierarchical channels within a lower iron content.The prepared FeAPO-34 molecular sieve with different iron content was used as a catalyst for hydroxylation of phenol.The catalytic results show that the increase of iron content can effectively increase the conversion of phenol and the selectivity of hydroquinone within a certain range,but the excessive iron content will lead to the increase of crystal size and affect the crystal agglomeration can not form hierarchical structure,Therefore,the molecular sieve with an iron content of 6.09%has the best catalytic performance,the phenol conversion rate is 41.7%and the selectivity of the hydroquinone is 92.7%.Furthermore,the potential of this system for the preparation of multi-hole high metal content catalysts has also been demonstrated.