Synthesis Of Aluminophosphate Molecular Sieves Using Eutectic Mixtures Composed Of Alcohol And Quaternary Ammonium Salts

Ionothermal synthesis, as a new method of preparing phosphate microporous materials,has the unique feature that the ionic liquid acts as both solvent and the template.Ionic eutectic mixture (EU) is usually composed of quaternary ammonium salts and hydrogen bonding donors.EUs exhibit unusual solvent properties that are very similar to those exhibited by ionic liquids, and could also be used in ionothermal synthesis as an alternative to ionic liquids. Quaternary ammonium salts are very attractive structure directing agents, however, using rencent eutectic mixtures in the synthesis of aluminophospate molecular sieves,quaternary ammonium cations can not play their template role, limiting the development of molecular sieves with new structures.So,it is very important to choose the appropriate EU to control the template role of the quaternary ammonium salts.Herein, the new EU composed of alcohol and quaternary ammonium salt were used to synthesize aluminophospate molecular sieves.The detailed synthesis conditions have been systematically investigated, and the typical samples have been characterized by XRD, SEM, CHN and TG The main contents and results are listed as follows:Firstly, aluminophospate molecular sieves have been successfully synthesized in the EUs composed of quaternary ammonium salts and pentaerythritol,and the results of thermogravimetric analysis and CHN elemental analysis showed that the quaternary ammonium cations were occluded in the channels as templates and could induce to form the structures of aluminophospates, different frameworks have been achieved by varying the quaternary ammonium salts.When the quaternary ammonium is tetramethylammonium chloride (TMAC1) or tetramethylammonium bromide (TMABr), aluminophospate UiO-7 has been synthesized, with ZON topology containing intersecting 8-ring channels parallel to the a and b crystallographic axes.UiO-7 could also be synthesized in the EU when the quaternary ammonium is Choline Cloride (ChCl).When the quaternary ammonium is tetraethylammonium chloride (TEAC1) or tetraethylammonium bromide (TEABr), aluminophospate AlPO4-5 has been synthesized, with AFI topology containing 12-ring channels fomed by alternate AlO4 and PO4 parallel to the c crystallographic axes.When the quaternary ammonium is 1,4-diethyl-1,4-dimethylpiperazinium dibromide (DMEPBr),aluminophospate UiO-7 has been synthesized.The SIZ-10 CHA framework consists of double six-membered rings (D6Rs) of alternating aluminum and phosphorus tetrahedra. These are linked through four-membered rings to produce a three-dimensional pore structure with eight-membered ring windows.Secondly, fluoride is an extremely useful mineralizer, it may help solubilize the starting materials under the reaction conditions and in some cases also play a structure directing role.In the EU composed of 1,1-dimethylpiperidinium chloride (DMPCl) and pentaerythritol, when the appropriate amount of HF was added to the initial reaction mixture, AlPO4-17 with the ERI topology containing 8-ring channels parallel to the b crystallographic axes was synthesized,without the addition of HF, AlPO4-22,with the AWW topology containing 8-ring pores channels parallel to the c crystallographic axes was synthesized.Thirdly, pentaerythritol was replaced by neopentyl glycol to investigate the effect of alcohols on the synthesis of aluminophospates.The results showed in the EU based on neopentyl glycol and quaternary ammonium salts,quaternary ammonium salts still determined the structure of the final products, solvent variation only affected the morphology of the samples.