AFI Molecular Sieves Formation Templated By Imidazolium-Based Ionic Liquids Under Ionothermal And Hydrothermal Conditions
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Date
2016-08
Authors
Ghoy, Jia Pei
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Abstract
Ferroaluminophosphate (FeAPO-5) and aluminophosphate (AlPO-5) molecular sieves of AFI topology have been successfully synthesized under ionothermal and hydrothermal conditions, respectively. The former approach employed 1-benzyl-2,3-dimethylimidazolium chloride ([bzm]Cl), as a structure-directing agent (SDA) while the latter used 1-benzyl-2,3-dimethylimidazolium hydroxide ([bzm]OH), 1-propyl-2,3-dimethylimidazolium hydroxide ([pm]OH) and 3-(2,3-dihydroxypropy)-1,2-dimethylimidazolium hydroxide ([dhm]OH) as the SDAs. The formation of FeAPO-5 under ionothermal condition using H3PO3 as a phosphorus source was investigated by spectroscopy and microscopy analyzes where the phenomenon involved induction, nucleation and crystallization processes. The results obtained showed that the incorporation of Fe3+ has enhanced the crystallization rate of FeAPO-5. During the crystallization process, FeNKX-2 intermediate was first obtained prior to phase transformation to FeAPO-5. The fast crystallization rate of FeAPO-5 was explained by the presence of Fe3+ as an intermediary electron-transfer medium promoting the fast release of phosphorus nutrient, P5+, from phosphite, P3+, a reservoir that required for the crystallization of FeAPO-5. A possible mechanism for the growth of FeAPO-5 crystals via new synthesis route was also proposed based on the experimental results and time-dependent studies. The hydrothermal synthesis of AlPO-5 was investigated by using
imidazolium-based SDAs containing three different functional groups. The results showed that the SDA molecules containing different functional groups of different polarity and molecular size had a significant effect on the rate of crystallization, degree of crystallinity, morphology and solid yield of the AlPO-5 crystals produced. The AlPO-5 crystals which were synthesized by using [dhm]OH, which had polar diol functionality, was found to have the highest rate of crystallization, the highest degree of crystallinity and highest solid yield compared to the case of using [pm]OH and [bzm]OH which contained less polar functional groups.
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AFI topology have been successfully synthesized under , ionothermal and hydrothermal conditions.