The state of iron sites in the calcined FeAlPO4-5 and its tuning to the property of microporous AlPO4-5 molecular sieve

Abstract

Please cite this article in press as: B. Feng, et al., The state of iron sites in the calcined FeAlPO 4 -5 and its tuning to the property of microporous AlPO 4 -5 molecular sieve, Catal. Today (2015), http://dx. a b s t r a c tThe dispersion and coordination is critical to the nature of metal phases. This article describes an approach of single Fe sites preparing under microporous environment via calcination of the Fe incorporated FeAlPO 4 -5 as well as the tuning to the property of AlPO 4 -5 molecular sieve. The UV, Raman, EPR spectroscopies and H 2 -TPR characterization revealed through the extraction of framework Fe inside the micropore by calcination, extra-framework Fe sites were generated, the dispersion of which was higher than Fe sites of impregnated Fe 2 O 3 /AlPO 4 -5, and it indicated that part of Fe sites of FeAlPO 4 -5 can be with coordination vacancy. It is notable that the presence of single Fe sites was directly observed by Cs-corrected STEM micrograph. NH 3 -TPD and toluene-TPD results both exhibited an enhanced acidity and bond adsorption ability of FeAlPO 4 -5 toward AlPO 4 -5 and the impregnated sample Fe 2 O 3 /AlPO 4 -5. Finally, the FeAlPO 4 -5 turned out to perform higher thiophene desulfurization rate against AlPO 4 -5 and impregnated sample, which can be related to the improvement in the adsorption ability and reactivity for the single Fe sites inside the microporous environment.

Morphology, Activation, and Metal Substitution Effects of AlPO4-5 for CO2 Pressure Swing Adsorption

“…A dominant peak centered at 263 nm is evident for all FeAPO-5 samples with a shoulder at 235 nm attributed to the ligand to metal charge transfer of Fe 3+ in [FeO 4 ] − tetrahedral geometry (Mohapatra et al, 2002 ). The intensity of the above band for the unsubstituted AlPO 4 -5 is negligible compared to the iron containing samples (Feng et al, 2016 ). Notably, for the sample with the highest metal content (10FeAPO-5) the above peak is shifted to higher wavelengths, which is indicative of increased amount of octahedral complexes in extra-framework positions, and the distribution state for the Fe species corresponding to 280 nm in particular can be isolated or clustered (Feng et al, 2016 ).…”

“…The intensity of the above band for the unsubstituted AlPO 4 -5 is negligible compared to the iron containing samples (Feng et al, 2016 ). Notably, for the sample with the highest metal content (10FeAPO-5) the above peak is shifted to higher wavelengths, which is indicative of increased amount of octahedral complexes in extra-framework positions, and the distribution state for the Fe species corresponding to 280 nm in particular can be isolated or clustered (Feng et al, 2016 ). The broad band between 400 and 500 nm is due to Fe d–d transitions and is also indicative of clustering of iron species (Wei et al, 2008 ).…”

Substituting effect of Ce3+ on the AlPO-11 molecular sieve

“…Both the number of Brønsted and Lewis acid sites increased, which was attributed to framework and extra-framework iron sites, respectively. 5 The acidity character had a close relationship with the coordination environment of the framework atoms. Wei et al observed the change of silicon distribution in SAPO molecular sieve after adding Mn 2+ ions.…”