Titration of active sites for partial oxidation of methanol over V2O5/SnO2 and MoO3/SnO2 catalysts by a low-temperature oxygen chemisorption technique

Reddy, Benjaram M.; Narsimha, K.; Sivaraj, Ch.; Rao, P. Kanta

doi:10.1016/s0166-9834(00)82310-6

Cited by 20 publications

(6 citation statements)

References 9 publications

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“…In addition, in situ Raman studies of the V 2 O 5 /SnO 2 catalyst for methane activation reaction indicated that the surface vanadia species on SnO 2 can be easily reduced with the presence of methane . The high reactivity of methanol partial oxidation over the V 2 O 5 /SnO 2 catalysts was also observed by Reddy et al Thus, it is possible that the V 2 O 5 /SnO 2 /SiO 2 and V 2 O 5 /CeO 2 /SiO 2 catalysts can be developed and that they will exhibit activities higher than those of the V 2 O 5 /TiO 2 /SiO 2 catalysts.…”

Section: Introductionsupporting

confidence: 63%

“…The coincidence of the IR and Raman bands suggests that isolated surface vanadia species containing one terminal VO bond and three bridging V−O−Si bonds are present. ,− The corresponding solid-state 51 V NMR shift appears at ∼640 ppm, which is consistent with tetrahedral coordination. , In situ XANES/EXAFS studies on V 2 O 5 supported on SiO 2 catalysts also suggest that the surface vanadia species on SiO 2 possess an isolated mono-oxo tetrahedral vanadate structure . From this structural characterization information, the sharp Raman band in the 1027−1038 cm -1 has been assigned to the isolated vanadate species possessing one terminal VO bond and three bridging VO support bonds. − The broad Raman band in the 900−920 cm -1 region has been assigned to polymeric tetrahedral metavanadate species. ,, However, the polymeric vanadate species also possess a VO terminal bond at 1027−1038 cm -1 , which is overlapping with the isolated vanadate species.…”

Section: Introductionmentioning

confidence: 98%

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Dynamic States of V₂O₅ Supported on SnO₂/SiO₂ and CeO₂/SiO₂ Mixed-Oxide Catalysts during Methanol Oxidation

Jehng

1998

J. Phys. Chem. B

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A series of V 2 O 5 supported on the SnO 2 /SiO 2 and CeO 2 /SiO 2 mixed oxides were investigated during methanol oxidation by in situ Raman spectroscopy, and the catalytic properties of these catalysts were probed by methanol oxidation kinetic studies. The Raman studies revealed that tin oxide forms a surface SnO x overlayer on the silica surface owing to the absence of Raman features of the SnO 2 crystallite, but cerium oxide forms bulk CeO 2 particles on the silica surface. The impregnated vanadium oxide formed a surface vanadia overlayer on all the catalysts owing to the absence of V 2 O 5 crystallite Raman features. In situ Raman studies of the V 2 O 5 /SnO 2 /SiO 2 and V 2 O 5 /CeO 2 /SiO 2 catalysts during methanol oxidation indicate that the formation of the VO x -SnO x and VO x -CeO 2 interactions totally blocks the formation of surface V-OCH 3 groups, which are observed in the V 2 O 5 /SiO 2 catalysts. The interaction between the surface VO x and the surface SnO x overlayer on silica increases the methanol oxidation reactivity by 1-2 orders of magnitude relative to V 2 O 5 /SiO 2 , and partial interaction between the surface VO x and bulk CeO 2 particles increases the methanol oxidation reactivity by 0-1 order of magnitude relative to V 2 O 5 /SiO 2 . Temperature programmed reduction (TPR) studies indicate that the reducibility of the surface vanadium oxide species is dependent on the reducibility of the specific oxide support and confirm the formation of the VO x -SnO x bonds for the V 2 O 5 /SnO 2 /SiO 2 catalyst and the formation of VO x -CeO 2 as well as VO x -SiO 2 bonds for the V 2 O 5 /CeO 2 /SiO 2 catalyst.

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Section: Introductionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 98%

Dynamic States of V₂O₅ Supported on SnO₂/SiO₂ and CeO₂/SiO₂ Mixed-Oxide Catalysts during Methanol Oxidation

Jehng

1998

J. Phys. Chem. B

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“…For extending this approach to surface modifications of materials, in this work we consider the SnO 2 -V 2 O 5 system. In fact, even this system is known from heterogeneous catalysis34567891011121314151617181920, with evidence that surface Sn-O-V bonds are the active species6. During the course of the study, a peculiar material structure was evidenced, featuring SnO 2 nanocrystals wrapped by V 2 O 5 -like layers.…”

mentioning

confidence: 99%

Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species

Epifani

Kačiulis

Mezzi

et al. 2017

Sci Rep

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9SnO 2 nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization techniques, it emerged that the as-prepared materials were constituted by cassiterite SnO 2 nanocrystals with a surface modified by isolated V(IV) oxide species. After heat-treatment at 400 °C, the SnO 2 nanocrystals were wrapped by layers composed of vanadium oxide (IV-V mixed oxidation state) and carbon residuals. After heating at 500 °C, only SnO 2 cassiterite nanocrystals were obtained, with a mean size of 2.8 nm and wrapped by only V 2 O 5 -like species. The samples heat-treated at 500 °C were tested as RhB photodegradation catalysts. At 10 −7 M concentration, all RhB was degraded within 1 h of reaction, at a much faster rate than all pure SnO 2 materials reported until now.Surface management is critical in such fields as heterogeneous catalysis, gas-sensors, photocatalysis and related applications, for obvious reasons of available reaction sites, and appears even more critical when complex systems are investigated. Indeed, several material features play a critical role in determining the final properties: the catalyst habit (i.e. size and shape, strictly correlated to dangling bonds of active species), surface oxygen vacancies (often correlated with in situ formation of active intermediates, such for instance peroxides), oxidation states of surface atoms are among the most relevant actors involved in reactant transformation during the process under investigation. It was recently highlighted 1,2 that classical heterogeneous catalysis can provide suggestive concepts of surface modifications. In fact, the nanocrystalline version of well-known combinations of catalytic oxides (COX) supported onto another metal oxide (support oxide, SOX) like TiO 2 -V 2 O 5 and TiO 2 -WO 3 , featured evident synergistic effects as concerns the enhancement of the gas-sensing response. It was argued that this occurred because, if the crystallite size of the SOX is decreased more and more, the relative electronic contribution generated by the reactions at the COX is increasingly important, due to the enhanced surface/volume atoms ratio in nanocrystalline materials. For extending this approach to surface modifications of materials, in this work

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“…Generally, the strength of interaction between the support and the active component governs the dispersion and hence oxygen uptake capacity. 16 The increased oxygen uptakes of VTiAl, VZrAl, and VLaAl catalysts may be due to an increase in the number of labile oxygen atoms on the catalyst surface, in other words an increase in the number of redox sites. Modification of alumina appears to have increased the reducibility of vanadia due to V-O-M bond formation.…”

Section: Resultsmentioning

confidence: 99%

Influence of Metal Oxide Modification of Alumina on the Dispersion and Activity of Vanadia Catalysts

Lakshmi¹,

Alyea²,

Srinivas³

et al. 1997

J. Phys. Chem. B

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Alumina was modified with 10 wt % MO x (MO x ) TiO 2 , ZrO 2 , La 2 O 3 , or MgO) prior to its impregnation with 12 wt % vanadia. The catalysts VTiAl, VZrAl, VLaAl, and VMgAl were characterized by X-ray diffraction (XRD), electron spin resonance (ESR), FT-Raman spectroscopy, 51 V solid state nuclear magnetic resonance ( 51 V NMR), and oxygen chemisorption. The activities of the catalysts were determined by methanol partial oxidation and their acid-base properties were evaluated for the decomposition of 2-propanol. XRD and FT-Raman spectroscopy indicated the formation of bulk TiO 2 and ZrO 2 on the titania and zirconia modified alumina. 51 V solid state NMR results suggest the presence of both octahedrally and tertrahedrally coordinated vanadia species in the catalysts VTiAl, VZrAl, and VAl and the presence of tetrahedrally coordinated vanadia species in the catalysts VLaAl and VMgAl. ESR spectra recorded at ambient temperature showed the presence of V 4+ ions having axial symmetry. Oxygen chemisorption results indicated an enhanced number of reducible vanadia sites, i.e., redox sites in the modified catalysts. Metal oxide modification is found to influence significantly the surface coverage and the methanol partial oxidation activity of vanadia supported on alumina. With proper MO x modification enhanced reducibility of vanadia could be attained, which in turn makes the partial oxidation reaction of methanol more facile.

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Titration of active sites for partial oxidation of methanol over V2O5/SnO2 and MoO3/SnO2 catalysts by a low-temperature oxygen chemisorption technique

Cited by 20 publications

References 9 publications

Dynamic States of V₂O₅ Supported on SnO₂/SiO₂ and CeO₂/SiO₂ Mixed-Oxide Catalysts during Methanol Oxidation

Dynamic States of V₂O₅ Supported on SnO₂/SiO₂ and CeO₂/SiO₂ Mixed-Oxide Catalysts during Methanol Oxidation

Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species

Influence of Metal Oxide Modification of Alumina on the Dispersion and Activity of Vanadia Catalysts

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Titration of active sites for partial oxidation of methanol over V2O5/SnO2 and MoO3/SnO2 catalysts by a low-temperature oxygen chemisorption technique

Cited by 20 publications

References 9 publications

Dynamic States of V2O5 Supported on SnO2/SiO2 and CeO2/SiO2 Mixed-Oxide Catalysts during Methanol Oxidation

Dynamic States of V2O5 Supported on SnO2/SiO2 and CeO2/SiO2 Mixed-Oxide Catalysts during Methanol Oxidation

Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species

Influence of Metal Oxide Modification of Alumina on the Dispersion and Activity of Vanadia Catalysts

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Dynamic States of V₂O₅ Supported on SnO₂/SiO₂ and CeO₂/SiO₂ Mixed-Oxide Catalysts during Methanol Oxidation

Dynamic States of V₂O₅ Supported on SnO₂/SiO₂ and CeO₂/SiO₂ Mixed-Oxide Catalysts during Methanol Oxidation