Structural evolution of dealuminated Y zeolites during various chemical treatments

Aouali, L.; Teanjean, J.; Dereigne, A.; Tougne, P.; Delafosse, D.

doi:10.1016/s0144-2449(88)80229-x

Cited by 35 publications

(13 citation statements)

References 13 publications

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“…Thus the exchange capacity of the material increases per unit of weight. These results on leaching are in agreement with the literature [32][33][34][35][36][37][38][39][40][41][42].…”

Section: Crystal Deagglomeration and Full Fe-exchangesupporting

confidence: 92%

“…In contrast to acid leaching, which removes framework Al [30,31], alkaline treatments preferentially extract Si, as initially reported by the Mobil Research & Development team [32][33][34]. Subsequently, several groups applied this technique in a more extended fashion [35][36][37][38][39][40][41][42]. There have been two major topics of interest: (i) aluminum zoning coupled with desilication and (ii) intracrystalline mesoporosity development to create hierarchical porous systems.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Utilizing full-exchange capacity of zeolites by alkaline leaching: Preparation of Fe-ZSM5 and application in N2O decomposition

Melián‐Cabrera

Espinosa

Groen

et al. 2006

Journal of Catalysis

112

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“…Thus the exchange capacity of the material increases per unit of weight. These results on leaching are in agreement with the literature [32][33][34][35][36][37][38][39][40][41][42].…”

Section: Crystal Deagglomeration and Full Fe-exchangesupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Utilizing full-exchange capacity of zeolites by alkaline leaching: Preparation of Fe-ZSM5 and application in N2O decomposition

Melián‐Cabrera

Espinosa

Groen

et al. 2006

Journal of Catalysis

112

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“…It is assumed that the use of additional HNO 3 caused the collapse of the framework structure and an amorphization of the material. 67 An acid treatment without phosphoric acid leads to severe amorphization as well ( Figure S13). Interestingly, the XRD patterns of sample [USY] P-ST , which are presented in Figure S13, do not show the formation of crystalline AlPO 4 .…”

Section: Faujasitementioning

confidence: 99%

Aluminum-Phosphate Binder Formation in Zeolites as Probed with X-ray Absorption Microscopy

et al. 2014

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In this work, three industrially relevant zeolites with framework topologies of MOR, FAU and FER have been explored on their ability to form an AlPO4 phase by reaction of a phosphate precursor with expelled framework aluminum. A detailed study was performed on zeolite H-mordenite, using in situ STXM and soft X-ray absorption tomography, complemented with (27)Al and (31)P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, XRD, FT-IR spectroscopy, and N2 physisorption. Extraframework aluminum was extracted from steam-dealuminated H-mordenite and shown to dominantly consist of amorphous AlO(OH). It was found that phosphoric acid readily reacts with the AlO(OH) phase in dealuminated H-mordenite and forms an extraframework amorphous AlPO4 phase. It was found that while AlPO4 crystallizes outside of the zeolitic channel system forming AlPO4 islands, AlPO4 that remains inside tends to stay more amorphous. In the case of ultrastable zeolite Y the FAU framework collapsed during phosphatation, due to extraction of framework aluminum from the lattice. However, using milder phosphatation conditions an extraframework AlPO4 α-cristobalite/tridymite phase could also be produced within the FAU framework. Finally, in steamed zeolite ferrierite with FER topology the extraframework aluminum species were trapped and therefore not accessible for phosphoric acid; hence, no AlPO4 phase could be formed within the structure. Therefore, the parameters to be taken into account in AlPO4 synthesis are the framework Si/Al ratio, stability of framework aluminum, pore dimensionality and accessibility of extraframework aluminum species.

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“…Acid treatment of zeolites is a well-known method to modify the Si/Al ratio by Al removal and creating mesoporosity [35,36]. In contrast, treatments using alkaline solutions remove preferentially silicon [37][38][39][40][41][42][43][44]. This will maintain the exchange capacity of the zeolite (Brønsted sites).…”

Section: Utilization Of Full Exchange Capacity Of Zeolitesmentioning

confidence: 99%

Innovations in the synthesis of Fe-(exchanged)-zeolites

2005

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Several aspects on the preparation of Fe-zeolites are discussed. In contrast to the many studies highlighting the characterisation of the active sites, new approaches for incorporation of Fe are presented.Full utilization of exchange capacity of zeolites has been achieved by a controlled alkaline treatment of the parent sample. With this method, iron can be fully exchanged by liquid phase ion-exchange on ZSM5 without the formation of inactive Fe-oxides.The second topic is the use of a mild oxidant (H 2 O 2 , and peroxides in general) to break down strong complexating equilibria during ionexchange by controlled redox titration of the ligands. Hydrogen peroxide oxidizes effectively chelating groups releasing Fe species at a controlled rate. The method is demonstrated for the preparation of Fe-FER through Ferric-citrate.The final concept discussed is the detemplating of the zeolite with the simultaneous incorporation of the iron (combined detemplation and ionexchange). This one-pot preparation minimizes the number of steps considerably. To realize this, a strong oxidant is necessary to remove the organic template, and Fe-cations for exchange. Both requirements are met with the Fenton's-chemistry (Fe 3+/2+ /H 2 O 2 mixtures) involving radical chemistry. #

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Structural evolution of dealuminated Y zeolites during various chemical treatments

Cited by 35 publications

References 13 publications

Utilizing full-exchange capacity of zeolites by alkaline leaching: Preparation of Fe-ZSM5 and application in N2O decomposition

Utilizing full-exchange capacity of zeolites by alkaline leaching: Preparation of Fe-ZSM5 and application in N2O decomposition

Aluminum-Phosphate Binder Formation in Zeolites as Probed with X-ray Absorption Microscopy

Innovations in the synthesis of Fe-(exchanged)-zeolites

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