Studies On The Ionothermal Synthesis Of Copper-containing Aluminophosphate Molecular Sieves And Their Catalytic Performance

Heteroatom-containing aluminophosphate molecular sieves are widely used in many applications?especially catalysis?owing to their structure selectivity and tunable active sites.Currently,molecular sieves are mainly synthesized by hydrothermal or solvothermal methods.Ionothermal synthesis developed recently has many advantages,such as negligible vapor pressure,safety,convenience,and high efficiency,which may well create new possibilities for the synthesis of molecular sieves.In this thesis,CuAPO-5 molecular sieves have been ionothermally synthesized and applied in the dehydration of fructose to HMF for the first time.The main results are as follows:1)CuAPO-5 molecular sieves with different Cu-doped amount have been synthesized in the ionic liquid 1-butyl-3-methylimidazolium bromide?[BMIM]Br?.Reaction variables have been adjusted systematically,such as kinds and amounts of amines,crystallization temperature and time.The results demonstrate that CuAPO-5?AFI phase structure?was formed in[BMIM]Br yet the products were CuAPO-11?AEL phase structure?in[EMIM]Br,which effectively confirms the structure-directing effect of ionic liquids.Furthermore,CuAPO-5 were synthesized with different relative crystallinity under the following variable conditions:various amines?n-DPA,TEA,n-BTA,TEAOH?,different amount of amine?mole ratio TEAOH/Al₂O₃=0.75,1.5,2.25 and 3.0?,different crystallization temperature?160-280??and different crystallization time?0.5-4h?.This shows that CuAPO-5 can be synthesized under a wide range of ionothermal conditions.Then the appropriate conditions of ionothermal synthesis CuAPO-5 with high crystallinity were confirmed:initial reactants including 1.0 Al₂O₃:2.55 P₂O₅:x Cu O:0.6 HF:20[BMIM]Br:1.5TEAOH?x=0,0.10,0.20,0.30,0.40?were synthesized at 190°C for 1h.2)The CuAPO-5 ionothermally synthesized has been applied in the dehydration of fructose to HMF with Ionic liquid as a reaction solvent and the effect of Cu-doped amount on the catalytic activity was studied.By evaluating catalytic performance and characterizing physicochemical properties of CuAPO-5,the structure-activity relationship of CuAPO-5 catalysts was preliminarily explored.Results were presented by following techniques:scanning electron microscopy?SEM?,N₂physical adsorption-desorption?BET?,electron spin resonance spectroscopy?ESR?,Fourier transform infrared spectroscopy?FT-IR?,ultraviolet-visible absorption spectroscopy?UV-Vis?,X-ray fluorescence spectroscopy?XRF?,NH₃-temperature programmed desorption?NH₃-TPD?.It has been demonstrated that the framework Cu species in the[Cu O₄]tetrahedral geometry were observed after the introduction of Cu²⁺,which results to the increasing acidity of the framework.However,the excessive dose of Cu²⁺unfortunately deposited on the external surface of framework or existed in the channels,which resulting in the decrease of the specific surface area and pore volume.Therefore,the combined action of Cu introduction results to the different catalytic activity of CuAPO-5 as shown below:CuAPO-5?0.10?>CuAPO-5?0.15?>CuAPO-5?0.05?>CuAPO-5?0.20?.The CuAPO-5?0.10?can obtain 90.6%yield of HMF,93.1%conversion of fructose and 97.3%selectivity of HMF?at 110°C for 120min?.