ChemInform Abstract: Characterization of V2O5—TiO2 Catalysts by Milling by ESR and Solid State 1H and 51V NMR.

Lapina, Olga B.; Шубин, А. А.; Nosov, A.; Bosch, Eric; Spengler, J.; Knoezinger, H.

doi:10.1002/chin.199950017

Cited by 4 publications

(26 citation statements)

References 1 publication

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“…The fitting of 27 Al MAS NMR spectra was carried out using Dmfit software 42 by implementation of Czjzek model (SzSimple) for simulation of quadrupole constant distribution. The 27 Al MAS NMR spectra have obviously no perfect quadrupole peak shape of crystalline materials; 43 thus, a correct Table 2. Relative Peak Ratio Obtained from the Decomposition of 15 kHz 29 Si MAS NMR Spectra in Figure 2 relative intensity (a.u.)…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…The surface OH group investigation by solid-state 1 H MAS NMR is widely applied for many materials, such as alumina, 13,14 silica, 15 aerogels, 16 zeolites, 17−21 titania, 22,23 heteropolyacids, 24 fiberglasses, 25,26 and vanadia. 27 The main drawback of 1 H NMR for surface OH groups is a sophisticated sample treatment prior to the experiment. Generally, the pretreatment requires high temperature dehydration under primary vacuum for several hours (4−12 h).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Many studies have been devoted to influence of hydration−rehydration on 27 Al NMR spectra. 38−41 Gaining better resolution of 27 Al NMR spectra requires hydration of the zeolites, which is accepted as a best practice prior to acquisition of 27 Al spectra of these materials. However, to study OH groups by 1 H NMR the samples should be dehydrated at elevated temperature and under vacuum conditions.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In this work, we try to establish a link between the results on various nuclei ( 1 H, 27 Al, and 29 Si) as a function of hydration state. The full hydration at 100% relative humidity and sample dying at 110 °C are discussed hereinafter.…”

Section: ■ Introductionmentioning

confidence: 99%

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Characterization of Catalytic Materials through a Facile Approach to Probe OH Groups by Solid-State NMR

Andreev

2017

J. Phys. Chem. C

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A facile NMR approach based on dipolar filtering (DF) and spin echo (SE) is proposed to study commercially available dealuminated USY zeolites, such as H-CBV760, H-CBV720, and NH4-CBV712 of nominal Si/Al ratio of 30, 15, and 6, respectively. The proposed 1H DF-SE magic angle spinning (MAS) NMR approach provides the substantial suppression of water signal intensity in partly hydrated samples providing an opportunity to obtain the signal of other surface groups. 1H DF-SE MAS NMR technique has been demonstrated its usability for quantitative (semiquantitative) analysis of dried, i.e., partly hydrated, samples. It is essential to use this approach when calcination under vacuum used as a reference procedure leads to drastic surface changes. Moreover, the technique is applicable for qualitative analysis of fully hydrated samples. This method is found to be extremely sensitive to the residual ammonium content in zeolite structure even in transformed to H form by calcination. Finally, the framework stacking faults species are found to be more pronounced in 1H DF-SE MAS NMR spectra in hydrated state as ∼1 ppm peak that can be crucial for understanding of relationships of structure and performance. Additionally, the “standard” 27Al and 29Si MAS NMR approaches are also discussed in both hydrated and dried states of zeolites. 29Si MAS NMR spectra demonstrate that a dependence on hydration state and the highest quantity of crystalline part is achieved in dried samples, whereas the best resolution of 27Al MAS NMR spectra is obtained in a fully hydrated state. Finally, a local order of Si framework given by full width at half-maximum parameter of crystalline Q4 0 peak correlates with increasing relative Al content, which is responsible for the distortion of zeolite structure.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Characterization of Catalytic Materials through a Facile Approach to Probe OH Groups by Solid-State NMR

Andreev

2017

J. Phys. Chem. C

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“…Indeed, it has been predicted that high levels of hydration can stimulate the leaching of OV(OH) 3 species. 46 Although previously proposed, 53 this study represents the first time that a fraction of vanadia species was distinctly observed as a dissolved vanadia species on the titania surface under hydrated conditions.…”

Section: ■ Results and Discussionmentioning

confidence: 56%

Impact of Hydration on Supported V₂O₅/TiO₂ Catalysts as Explored by Magnetic Resonance Spectroscopy

Jaegers

Wang

et al. 2021

J. Phys. Chem. C

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Supported vanadium oxide catalysts are important industrial materials for a wide array of chemical transformations. The condition of surface hydration is of particular interest as a reflection of the state of freshly manufactured catalysts prior to their activation in catalytic reactors or under the conditions of photocatalysis where surface vanadia are exposed to moisture. Under such conditions, the surface vanadia species undergo structural changes, as evidenced by 51V magic-angle spinning nuclear magnetic resonance (51V MAS NMR) in this study. For low surface vanadia densities on titania, a modest trend toward the formation of dimeric and oligomeric vanadia species was observed under hydrated conditions when compared to the corresponding dehydrated catalyst, which contains a large abundance of monomeric vanadia species. The incorporation of tungsten oxide into the V2O5/TiO2 catalyst with low surface vanadia density, however, is found to better stabilize the surface vanadia species on the titania support upon hydration than its tungsta-free counterpart. This stabilization is not an intrinsic property of more extensively oligomerized surface vanadia species in the presence of tungsten oxide, which is evidenced by the conditions of high concentrations of surface vanadia oligomers on titania that exhibit dramatic structural changes upon hydration. At high surface vanadia coverage under hydrated environments, the simultaneous observation of polycrystalline V2O5 nanoparticles and a mobile phase of surface vanadia species is apparent, where vanadia species are dissolved in a thin hydration layer on the titania support. These new findings have broad implications on the behavior of other metal-oxide species on high surface oxide supports under hydrated conditions.

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Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NO_x Emissions with NH₃

et al. 2021

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Supported V2O5–WO3/TiO2 materials are employed as selective catalytic reduction (SCR) catalysts for NO x emission control from power plants. Fresh SCR catalysts usually receive exposure to harsh treatments in the industry to accelerate catalyst activation (calcination in air at 650 °C) and catalyst aging (hydrothermal aging at 650 °C) in a way that represents various points in the catalyst/product lifetime. The present study investigates the catalyst structural and chemical changes occurring during such harsh treatments. Three series of supported V2O5–WO3/TiO2 catalysts were prepared by incipient-wetness impregnation of aqueous ammonium metavanadate and metatungstate precursors. The catalysts were subsequently dried and calcined at 550 °C in O2, 650 °C in O2, and hydrothermal conditions (10% O2, 8% H2O, 7% CO2, and 75% N2) at 650 °C. The resulting catalysts were physically characterized by numerous techniques (in situ Raman; in situ IR; in situ high-field–high-spinning solid-state 51V MAS NMR; in situ electron paramagnetic resonance; X-ray diffraction; Brunauer, Emmett, and Teller surface area; and inductively coupled plasma) and chemically probed with adsorbed ammonia, SCR–TPSR, and the SCR reaction. The surface WO x sites on the TiO2 support behave as a textural promoter that stabilizes the TiO2 (anatase) phase from sintering and transforming to the undesirable crystalline TiO2 (rutile) phase that can lead to formation of a Ti1–x V x O2 (rutile) solid solution with reduced V4+ cations (∼7–15%). The surface VO x sites are mostly oligomerized as surface V5+O x sites (∼50–85% oligomers) and the extent of oligomerization tends to increase with surface WO x coverage and calcination temperature. A major difference between the calcined and hydrothermally treated catalysts was the low concentration of surface NH3 * species on Lewis acid sites for the hydrothermally treated catalysts, yet the SCR activity was almost comparable for both catalysts. This finding suggests that surface NH4 +*, primarily associated with the surface VO x sites, are able to efficiently perform the SCR reaction. Given that multiple catalyst parameters were simultaneously varying during these treatments, it was difficult to correlate the SCR activity with any single catalyst parameter. A correlation, however, was found between the SCR TOF/activity and the sum of the surface NH3 * and NH4 +* species, which is dominated by the surface NH4 +* species.

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ChemInform Abstract: Characterization of V₂O₅—TiO₂ Catalysts by Milling by ESR and Solid State ¹H and ⁵¹V NMR.

Cited by 4 publications

References 1 publication

Characterization of Catalytic Materials through a Facile Approach to Probe OH Groups by Solid-State NMR

Characterization of Catalytic Materials through a Facile Approach to Probe OH Groups by Solid-State NMR

Impact of Hydration on Supported V₂O₅/TiO₂ Catalysts as Explored by Magnetic Resonance Spectroscopy

Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NO_x Emissions with NH₃

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ChemInform Abstract: Characterization of V2O5—TiO2 Catalysts by Milling by ESR and Solid State 1H and 51V NMR.

Cited by 4 publications

References 1 publication

Characterization of Catalytic Materials through a Facile Approach to Probe OH Groups by Solid-State NMR

Characterization of Catalytic Materials through a Facile Approach to Probe OH Groups by Solid-State NMR

Impact of Hydration on Supported V2O5/TiO2 Catalysts as Explored by Magnetic Resonance Spectroscopy

Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NOx Emissions with NH3

Contact Info

Product

Resources

About

ChemInform Abstract: Characterization of V₂O₅—TiO₂ Catalysts by Milling by ESR and Solid State ¹H and ⁵¹V NMR.

Impact of Hydration on Supported V₂O₅/TiO₂ Catalysts as Explored by Magnetic Resonance Spectroscopy

Structure–Activity Relationships of Hydrothermally Aged Titania-Supported Vanadium–Tungsten Oxide Catalysts for SCR of NO_x Emissions with NH₃