... O 28 ] 6− decavanadate polyoxoanion and a novel [Al 4 (OH) 6 (H 2 O) 12 ] 6+ polyoxocation. * E-mail: akampf@nhm.org . Manuscript handled by G. Diego Gatta 17 3 2021 16 6 2021 Copyright © 2022 by the Mineralogical Society of America 2022 Mineralogical Society...

... vanadoaluminate heteropolycation (“flat-Al 10 V☐ 2 ”), ideally [(V 5+ O 2 )Al 10 (OH) 20 (H 2 O) 18 ] 11+ , closely related to the technologically important flat-Al 13 polyoxocation. * E-mail: akampf@nhm.org Manuscript handled by G. Diego Gatta 25 6 2019 31 8 2019 Copyright © 2020...

...-pillared smectites modified with Ce and La. Pillaring of clays with Al polyoxocations (Keggin type Al 13 ) and a large variety of other complexing cations has been reported many times since the seventies. McCauley (1988) described in a patent the preparation of thermally stable pillared clays with large...

... chloride ions which could prevent the diffusion of polyoxocations within the interlayer space ( Palinko et al. , 1996 ). The solid was air dried and the resulting product was calcined for 2 h at different temperatures. The conditions used in the preparation of all the materials described are shown...

...-exchanges and dissociations at the solution-oxide interface. Here we suggest the feasibility of making other heteroatom substitutions in the MAl 12 class of polyoxocations ( Johansson 1960 ), having the stoichiometry [MO 4 Al 12 (OH) 24 (H 2 O) 12 ] 6/7/8/+ and having the ɛ-isomer structure...

...Fig. 1. Powder XRD patterns of Mt clay exchanged with Al polyoxocations at different ratios (R) of mmol of Al/g of clay: (a) R = 0, (b) R = 3, (c) R = 6, (d) R = 12 and (e) R = 24. ...

...) that are made up of dimers of δ-Keggin structure, which have one trimeric group rotated so that its Al(O) 6 polyhedra share corners with the rest of the molecule, not edges as in the ε-Keggin structure. The δ-Keggin isomer of the Al 13 molecule is a key intermediate in the formation of larger polyoxocations...

... crystallize by accretion of metastable dissolved polyoxocations ( Fu et al. , 1991 ; Bradley et al. , 1993 ; Bradley and Hanna, 1994 ) and not from de novo nucleation from dissolved monomers in solution. Using spectroscopy, metastable dimers, trimers, and multimeric polyoxocations have been identified...

... Alkoxide Clays PILCs Review Synthesis TiCl 4 Titanium The use of inorganic hydrated polyoxocations as pillaring agents provided thermally stable pillared clays with large specific surface areas ( Kloprogge, 1998 ). Several single and mixed-oxide pillars have been prepared using...

...F ig . 4. Polyhedral representation of the Al 13 O 4 (OH) 24 (OH 2 ) 12 7+ (aq) polyoxocation, which has a structure similar to an ε-Keggin molecule. The solid symbols (•) denote a six-membered ring of edge-shared AlO 6 octahedra to be compared with Fig. 2 . ...

... the plane in Figs. 9a and 9b ) are considered less reactive as they are bound to the underlying TOT layer via hydrogen bonds. Work on the mechanism of oxygen exchange on the alumina ɛ-keggin polyoxocations has revealed an alternate hypothesis. These molecules are composed of sets of three aluminum...

... Pillared clays (PILCs) are porous materials obtained by intercalation with bulky polyoxocations of swelling clays, mainly montmorillonites. After calcination at temperatures usually in the range 350–500°C, the intercalated polyoxocations are transformed into rigid oxide pillars, giving pillared clays...

... thermal and hydrothermal stability. The search for such systems resulted in renewed interest in the concept of pillared clays. The use of inorganic hydrated polyoxocations as pillaring agents provided thermally stable pillared clays with large specific surface areas ( Kloprogge, 1998 ). On the other...