Characterization of FeAPO-5 molecular sieve in the presence of HF and its catalytic performance for phenol hydroxylation

Iron-substituted aluminophosphate molecular sieves (FeAPO-5) were synthesized by hydrothermal crystallization conventionally or in the presence of fluoride ion, respectively. Those synthesized molecular sieves were characterized by X-ray diffraction (XRD), scanning electron spectroscopy (SEM), Fourier transform infrared (FT-IR) spectrometer, ultraviolet visible spectroscopy (UV-vis), electron spin resonance (ESR) and hydrogen temperature programmed reduction (H₂-TPR). The results revealed that the crystallinity and BET of synthesized samples increased apparently in the presence of F⁺. The Fe³⁺ was mainly present in the framework sites of FeAPO-5 molecular sieves, but more unsaturated co-ordinate framework Fe (III) was present in FeAPO-5 by adding HF. Moreover, the FeAPO-5 synthesized in the presence of F⁺ exhibited higher catalytic activity in the phenol hydroxylation than that of synthesized conventionally.