The Ionothermal Synthesis And Charaterization Of Phosphates Molecular Sieves

Crystalline porous materials such as zeolites are of interest in a number ofareas of modern science, particularly those associated with catalysis, gas storage,ion exchange and so on. The modern industrial application presents us a newchallenge with regard to the framework and properties of molecular sieves. It isalways international focus to explore new zeolites with new structures. To ourknowledge, the different chemistry of the solvents has a notable effect on thestructures and properties of the molecular sieves. Ionic liquids or deep eutecticmixtures as the green solvent on the synthesis of the molecular sieves haveattracted focus over recent years, due to their special properties such asnegligible vapor pressure, high conductivity, product separation, high solubilityand so on, as well as plenty of different chemistry of usable ionic liquidsprovided more chance for the synthesis of molecular sieves with novelframework. Aiming at preparing molecular sieves with nove framework byionothermal method, we investigated the possibility and synthetic rule ofpreparation of aluminium phosphate and zinc phosphate molecular sieves indeep eutectic mixture based on benzoic acid/choline chloride, urea/quaternaryammonium salts(tetramethylammonium chloride, tetraethylammonium bromide,tetrapropylammonium bromide, choline chloride), 1,3-dimethylurea/tetraethyl-ammonium bromide, 1,3-dimethylurea/1,1-dimethylpiperidinium chloride. Thetypical samples were characterized by XRD, SEM, TG and FT-IR. The mainresults are listed as follows.Firstly, the molecular sieve ZON with 8-ring windows could be synthesizedin the deep eutectic mixture system of HF-Al₂O₃-P₂O₅-benzoic acid/cholinechloride. The conditions in the synthesis of molecular sieve ZON were:Al₂O₃:P₂O₅:EU:F^-=14.7:31:322:1(mol ratio), crystallization temperature of180℃and crystallization time of 3days. The molecular sieve ZON was hexagonsheet crystal accumulation up to 160×140μm. It belonged to orthorhombic withspace group Pbca(61), a=14.546(3)(?), b=15.190(3)(?), c=16.550(3)(?). It wasproved that molecular sieves could be synthesized in the new solvent formed bybenzoic acid/choline chloride, which acted as the roles of solvent and template.Secondly, the feasibility of the synthesis of aluminium phosphate molecularsieves with novel frameworks in the deep eutectic mixtures based onurea/quaternary ammonium salts was studied by ionothermal synthesis, as wellas the influences of the compositions of reaction mixture. The experimentalresults showed that molecular sieve AlPO₄-CJ₂ could be synthesized in thedifferent deep eutectic mixtures when the chemical compositions of reagentswere Al:EU=0.07:1(mol ratio) and P/Al was appropriate, and crystallizationtemperature and time were 180℃and 3days, respectively. Because of the influence of the ammonium, which is partial decomposition of the urea, noaluminium phosphate molecular sieve with different frameworks wassynthesized by changing different quaternary ammonium salts.Thirdly, the large single crystals of molecular sieve (NH₄)ZnPO₄-HEXcould be synthesized in the deep eutectic mixture system of P₂O₅-HF-ZnO-urea/choline chloride. The optimum parameters in the synthesis of molecular sieve(NH₄)ZnPO₄-HEX were: P : F^-: Zn : EU=2.57 : 5.31 : 1 : 167(mol ratio),crystallization temperature of 180℃and crystallization time of 69h. The largesingle crystals of molecular sieve (NH₄)ZnPO₄-HEX up to 130×30×30μm wereof high transparency, whose both sides were perfect hexagonal prismatic shapesand the middle was prism. It belonged to hexagonal system with space groupP63, a=10.70(?), b=10.70(?), c=8.71(?),α=90°,γ=120°. It was proved that zincphosphate molecular sieves could be synthesized in the deep eutectic mixturebased on urea/choline chloride.Fourthly, the molecular sieve ZnPO₄-1 with unknown structure could besynthesized in the deep eutectic mixture system of P₂O₅-HF-ZnO-1,3-dimethyl-urea/tetraethylammonium bromide. The optimum parameters in the synthesis ofmolecular sieve ZnPO₄-1 were: P:F^-:Zn:EU=2.23:1.83:1:43.12(mol ratio),crystallization temperature of 180℃and crystallization time of 3days. Thesingle crystals of molecular sieve ZnPO₄-1 were cuboid shape up to150×90×20μm. The crystal data: a=13.89(?), b=7.05(?), c=6.69(?),α=β=γ=90°.Finally, the molecular sieve ZnPO₄-2 with unknown structure could besynthesized in the deep eutectic mixture system of P₂O₅-HF-ZnO-1,3-dimethyl-urea/1,1-dimethylpiperidinium chloride. The optimum parameters in thesynthesis of molecular sieve ZnPO₄-1 were: P:F^-:Zn:EU=2.23:2.29:1:47.65(molratio), crystallization temperature of 180℃and crystallization time of 3days.The single crystals of molecular sieve ZnPO₄-2 were club-shaped up to60×14×3μm.