Identification, Stability, and Reactivity of NOx Species Adsorbed on Titania-Supported Manganese Catalysts

Kantcheva, Margarita

doi:10.1006/jcat.2001.3413

Cited by 247 publications

(190 citation statements)

References 40 publications

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“…The nitrosonium ion, NO + , chemisorbed on titania (anatase) and monoclinic zirconia gives rise to absorption band at 2206-2210 cm −1 [44,46,[56][57][58][59]. The low intensity of the band attributed to the NO + species adsorbed on the ZrO 2 sample used in this study leads to the conclusion that the surface nitrates are obtained mainly by disproportionation of NO 2 with the involvement of the isolated hydroxyls at 3740 and 3693 cm −1 (reaction (5)).…”

Section: Coadsorption Of No and Omentioning

confidence: 69%

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Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Kantcheva

Çayırtepe

2006

Journal of Molecular Catalysis A: Chemical

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Surface species obtained during the adsorption of NO and NO/O 2 coadsorption at room temperature on Pd-free (WZ) and Pd-promoted tungstated zirconia (Pd/WZ) are identified by means of in situ FT-IR spectroscopy. The WZ and Pd/WZ samples have a tetragonal structure and contain randomly distributed mesoporous phase. Dispersed palladium(II) species are present in two different environments: (i) Pd 2+ ions, which have only Zr 4+ ions in their second coordination sphere and (ii) Pd 2+ ions, which are linked to both zirconium and tungsten ions via oxygen bridges. On the Pd/WZ sample, NO undergoes oxidation to various NO x species depending on the temperature. The compounds formed at room-temperature oxidation are adsorbed N 2 O 3 and products of its self-ionization, NO + and NO 2 − . In this process W(VI) is involved, being reduced to W(IV). At high temperature N 2 O 3 decomposes, restoring the W O species. Under these conditions, NO undergoes oxidation to NO 2 by the Pd(II) ions, which are reduced to Pd(I). The nitrosyls of Pd(I) display high thermal stability and do not disappear upon evacuation at 623 K. During NO/O 2 coadsorption on the Pd/WZ catalyst at room temperature, the amounts of surface nitrates and NO 2 /N 2 O 4 formed in the gas phase are significantly lower than those observed under identical conditions in the presence of tungstated zirconia. It is concluded that promotion of tungstated zirconia with palladium(II) suppresses the oxidation of NO by molecular oxygen at room temperature due to the elimination of acidic protons involved in the process.

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Section: Coadsorption Of No and Omentioning

confidence: 69%

“…Similar process (Eq. (5)) has been proposed to take place upon interaction of NO 2 with oxides containing basic OH groups such as titania (anatase) [56][57][58] and monoclinic zirconia [44,46]:…”

Section: Coadsorption Of No and Omentioning

confidence: 99%

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Kantcheva

Çayırtepe

2006

Journal of Molecular Catalysis A: Chemical

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“…On the basis of the numerous former studies in the literature, [39][40][41][42] these bands can be attributed to bidentate (1582 cm -1 ) and bridged (1628 cm -1 ) nitrates located on the Ti 4+ sites of the Ti/Al(P1) surface. It should be noted that the argument regarding the presence of different nitrate species adsorbed on the Ti/ Al(P1) sample with different adsorption sites and adsorption geometries, is in very good agreement with our previous studies on the structure and the surface acidity of the Ti/Al(P1) system.…”

Section: No X Adsorption On Ti/al Support Materials Via Ftir Spectrosmentioning

confidence: 99%

Fine-Tuning the Dispersion and the Mobility of BaO Domains on NO_x Storage Materials via TiO₂ Anchoring Sites

2010

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In an attempt to control the surface dispersion and the mobility of BaO domains on NO x storage materials, TiO 2 /TiO x anchoring sites were introduced on/inside the conventional γ-Al 2 O 3 support matrix. BaO/TiO 2 / Al 2 O 3 ternary oxide materials were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies. The synthesized NO x storage materials were studied via XRD, Raman spectroscopy, BET surface area analysis, TPD, XPS, SEM, EDX-mapping, and in situ FTIR spectroscopy of adsorbed NO 2 . NO x uptake properties of the BaO/TiO 2 /Al 2 O 3 materials were found to be strongly influenced by the morphology and the surface structure of the TiO 2 /TiO x domains. An improved Ba surface dispersion was observed for the BaO/TiO 2 /Al 2 O 3 materials synthesized via the coprecipitation of alkoxide precursors, which was found to originate mostly from the increased fraction of accessible TiO 2 /TiO x sites on the surface. These TiO 2 /TiO x sites function as strong anchoring sites for surface BaO domains and can be tailored to enhance surface dispersion of BaO. TPD experiments suggested the presence of at least two different types of NO x species adsorbed on the TiO 2 /TiO x sites, with distinctively different thermal stabilities. The relative stability of the NO x species adsorbed on the BaO/TiO 2 /Al 2 O 3 system was found to increase in the following order: NO + /N 2 O 3 on alumina , nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO 2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO 2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO 2 domains.

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“…(Fig.1) leads to appearance of growing bands in the carbonate/carboxylate region. The broad band at 1410 cm -1 is attributed to the ν3 vibration of mono-dentate carbonates [13,14]. Weak absorptions at 2900, 2800 and 2600 cm -1 together with the band at 1500 cm -1 are typical of tartrate species [13,14].…”

Section: Infrared Spectramentioning

confidence: 95%

“…The broad band at 1410 cm -1 is attributed to the ν3 vibration of mono-dentate carbonates [13,14]. Weak absorptions at 2900, 2800 and 2600 cm -1 together with the band at 1500 cm -1 are typical of tartrate species [13,14]. The former three bands are due to Fermi resonance between the ν(CH) fundamental and combinations or overtones of bands in the carboxylate region.…”

Section: Infrared Spectramentioning

confidence: 96%

A Novel Technique for Synthesis A Thermal Barrier Coating Material of Lanthanum -Magnesium Hexaaluminate (LaMgAlllO19)

Mohsen¹

2014

IJIRSET

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ABSTRACT:As the advances in some industrial applications are leading to higher operating temperatures; materials of metallic coatings that withstand harsh environments at high temperature are developing. One of the most promising compounds, which can be used as a material for thermal barrier coatings (TBCs) is lanthanum magnesium hexaaluminate (LaMgAl l1 O 19 ).The objective of this study, was to synthesize LaMgAl ll O 19 through a technique of tartaric acid precursor. Effect of different annealing temperature on the microstructure has been studied and reported in the presented research. The annealing temperature was controlled from 900-1300 o C. Kinetic calculations confirmed by the experimental data from the thermal analyses were used to assess the nature of the resultant compound. Interpretation of FT-IR and XRD spectra combined with SEM-EDX observations have identified that a pure single phase was successfully obtained at 1100 o C.

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Identification, Stability, and Reactivity of NOx Species Adsorbed on Titania-Supported Manganese Catalysts

Cited by 247 publications

References 40 publications

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Fine-Tuning the Dispersion and the Mobility of BaO Domains on NO_x Storage Materials via TiO₂ Anchoring Sites

A Novel Technique for Synthesis A Thermal Barrier Coating Material of Lanthanum -Magnesium Hexaaluminate (LaMgAlllO19)

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Identification, Stability, and Reactivity of NOx Species Adsorbed on Titania-Supported Manganese Catalysts

Cited by 247 publications

References 40 publications

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

Fine-Tuning the Dispersion and the Mobility of BaO Domains on NOx Storage Materials via TiO2 Anchoring Sites

A Novel Technique for Synthesis A Thermal Barrier Coating Material of Lanthanum -Magnesium Hexaaluminate (LaMgAlllO19)

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Fine-Tuning the Dispersion and the Mobility of BaO Domains on NO_x Storage Materials via TiO₂ Anchoring Sites