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VSiβ zeolites prepared by contacting dealuminated Siβ zeolite with aqueous solutions of ammonium metavanadate at room temperature have been studied by diffuse reflectance UV-visible and photoluminescence spectroscopy. UV-visible spectroscopy shows that whatever the vanadium content, vanadium is present in as-prepared VSiβ in only one kind of tetrahedral coordination. After calcination and then rehydration of VSiβ with low V content, still only one kind of tetrahedral V V species is observed. However, in calcined/ rehydrated VSiβ with high V content, two kinds of tetrahedral and one kind of octahedral V species are revealed. In contrast, photoluminescence spectroscopy in static or dynamic mode can distinguish in as-prepared VSiβ three kinds of tetrahedral vanadium species. Their relative amounts depend strongly on the vanadium content and on calcination/rehydration treatments. They are present at two different types of framework sites. For samples with low V loading, the tetrahedral V V species are in a site poorly accessible to water, probably in the five-membered rings of the β structure. These V V species are little sensitive to calcination/rehydration treatments. In contrast, for higher V loading, the tetrahedral V V species become highly sensitive to such treatments suggesting that V V ions are in a site more accessible to water, probably in the 12-membered rings, where they can easily change their coordination upon dehydration/rehydration processes. Possible models of tetrahedral and octahedral V species and their probable location in the β structure are proposed.

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Tantalum-containing SiBEA zeolite with isolated framework mononuclear Ta(V) doped with Ag, Cu and Zn were prepared and characterized by XRD, XPS, DR UV-VIS and FTIR (with 2 of additional dehydrogenation sites. Such modification allows accelerating ethanol dehydrogenation to acetaldehyde and subsequent steps of the ethanol-to-butadiene process.Ethanol conversion and butadiene selectivity over the catalysts increase in the order: TaSiBEA < ZnTaSiBEA < AgTaSiBEA < CuTaSiBEA. Higher selectivity to butadiene (73 %) was achieved over CuTaSiBEA (at 88% ethanol conversion, T = 598 К, WHSV = 0.5 h -1 ). 22ASSOCIATED CONTENT Supporting Information. The details of the calculations of the amount of recycled CO 2 in 1,3-butadiene production from biomass, XP spectra, TEM images and diffraction patterns, additional catalytic results. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Authors* E-mails: pavlo_kyriienko@ukr.net (P.K.) and stanislaw.dzwigaj@upmc.fr (S.D.).

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The presence of different vanadium species in VSiβ zeolite is evidenced by diffuse reflectance UV-visible and photoluminescence spectroscopies, but only the latter is able to clearly distinguish three kinds of tetracoordinated vanadium sites and to reveal the effects of V loading and dehydration-hydration processes on the environment of the V species.

The dealumination of BEA zeolite by treatment with concentrated nitric acid is evidenced by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Two-dimensional 27Al 3Q and 5Q magic-angle-spinning (MAS) NMR allow the detection of two kinds of tetrahedral Al atoms whose relative amounts depend on the Si/Al ratio and which correspond to two specific T-sites. 29Si MAS NMR and 1H MAS NMR measurements confirm these results. 29Si MAS NMR spectra evidence two resonances at around −114 and −111 ppm ascribed to Si sites of the Si(OSi)4 environment of two different crystallographic sites. Moreover, the presence of Si atoms associated with hydroxyl groups is confirmed by a resonance at −102 ppm when 1H−29Si CP is applied. The Brønsted and Lewis acidic sites in dealuminated BEA zeolites are evidenced by FTIR spectra of adsorbed pyridine which show two kinds of bridging hydroxyl groups (Si−O(H)−Al) of different acid strength. 51V MAS NMR confirms the incorporation of vanadium atoms into vacant T-atom sites of a fully dealuminated SiBEA zeolite leading to two kinds of tetrahedral V(V) sites (δiso = – 708 and – 766 ppm), with a V=O double bond and linked by V−OSi bonds to the framework. The two types of tetrahedral V(V) sites are in line with the two kinds of tetrahedral Al sites initially present in the zeolite. Moreover, the two bands at 3620 and 3645 cm−1 suggest that VSiBEA also contains V(V) sites with V(V)O−H groups, which exhibit Brønsted acidic character as shown by FTIR of adsorbed pyridine. Possible ways for the formation of tetrahedral V(V) in the BEA structure are proposed.