Temperature-programmed desorption/reaction and in situ spectroscopic studies of vanadia/titania for catalytic reduction of nitric oxide

Srnak, T. Z.

doi:10.1016/0021-9517(92)90283-n

Cited by 120 publications

(84 citation statements)

References 34 publications

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“…This fact shows that there is a preference in blocking of strong Lewis sites of the support during the adsorption of VO3-species. This is in agreement with previous publication^(^, 13) and could explain the TPR evidences for the stronger interaction between vanadium0x0 species and the titania surface in the VOx/ Ti02-EDF sample.…”

Section: Resultssupporting

confidence: 93%

VANADIUM‐TITANIUM OXIDE CATALYSTS. INFLUENCE OF THE PREPARATION METHOD ON THE o‐XYLENE SELECTIVE OXIDATION

Georgiadou

Slavov

Papadopoulou

et al. 1995

Bulletin des Soc Chimique

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Vanadium oxide supported on titania catalysts prepared by the "Equilibrium Deposition followed by Filtration" method (EDF) and the conventional Wet-impregnation method (WI) were extensively characterized by the joint use of various physicochemical techniques (BET, XRD, FT-IR, DRS, XPS, AEM, TPR, and TPD of NH3 ) and were tested for the partial gas-phase oxidation of o-xylene. It was found that the EDF method leads to more selective monolayer catalysts. The increased selectivity has been attributed to the reduction of the surface acidity, to the enhancement of the Vv/ VIV ratio and to the redox properties induced in this catalyst by the above preparation method In the present work we report for the first time the influence of the EDF preparation method on the physicochemical characteristics of VOx/ Ti02 catalysts as well as on their performance for selective gas-phase oxidation of o-xylene to phthalic anhydride. EXPERIMENTALCatalysts preparation: Two different VOx/ Ti@ catalysts were prepared. Ti02 (Degussa P-25, SSA : 50 rn2g-l, average particle size : 3Onm, 80% anatase) was used as the support in both cases. In order to prepare the VOx/"i02-EDF sample an amount of Ti02 powder equal to 5.4 g was suspended in a NH4V03 aqueous solution of 1.5~10-3 mol V dm-3, volume totaling 2.5 dm3. The ionic strength of the solution was adjusted to 0.1 mol dm-3 by NH4N03 while the suspension pH was regulated at 4.5 using HN03. This suspension was stirred at constant temperature (25OC) for 24 h and then filtered through membrane filters [Millipore, 0.22ml. The solid was dried at 12OOC for 2.5 h. Then it was calcined at 500OC for 5 h in air. The filtrate was analyzed spectrophotometrically [Varian, Cary-3,UV-VISI for Vanadium at 392 nm.The second sample (VOx/ Ti@-WI) was prepared by the conventional wet-impregnation method. A calculated amount of vanadyl oxalate to give the same V-loading on the final catalyst with that of the VOx/ Ti02-EDF sample was diluted in 100 cm3 of H20 . 3.8g of Ti02 support was added and the H20 was removed in a rotary evaporator under vacuum at 8OoC within 4 h. The solid underwent the same thermal treatment as described above. These preparation steps were repeated several times in order to prepare about 30 g of each catalyst. This amount was necessary for the activity tests.-143 -Phvsicochemical characterization: The specimens prepared were characterized using (i) the BET method (adsorbed gas: N2) to determine the specific surface area (SSA), (ii) X-ray diffraction patterns obtained with a powder X-ray diffractometer (Philips PC automated, radiation: Cu-Ka filtered through Ni, range: 10<28/degree<75) to investigate the formation of crystal phases, (iii) FT-IR spectra of the samples in the form of tamplets with KBr recorded with a FT-IR spectrophotometer (Perkin-Elmer 16 PC) to study the structure of the supported species, (iv) X-ray photoelectron Powder X-ray diffraction patterns of these samples revealed that no characteristic XRD peak is found due to the V-oxide phase. However, since the possib...

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Section: Resultssupporting

confidence: 93%

VANADIUM‐TITANIUM OXIDE CATALYSTS. INFLUENCE OF THE PREPARATION METHOD ON THE o‐XYLENE SELECTIVE OXIDATION

Georgiadou

Slavov

Papadopoulou

et al. 1995

Bulletin des Soc Chimique

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“…[51][52][53][54][55][56] Here, experimental techniques such as temperature programmed desorption (TPD), 51 Fourier transform infrared spectroscopy (FTIR), [52][53][54] and combined TPD-FTIR 55,56 have been applied. After adsorption of NH 3 at the V 2 O 5 (010) surface two different surface species have been discussed.…”

Section: Resultsmentioning

confidence: 99%

“…9 Ammonia adsorption energies were estimated to be in the range between −0.8 eV and −1.1 eV. 55 In a number of experimental studies on NH 3 adsorption at vanadium oxide surfaces, additional spectroscopic features have been found which could indicate the presence of a surface amide, NH 2 . 54,59,60 This species, in addition to coordinated ammonia and NH 4 + at the surface, was also suggested by nuclear magnetic resonance (NMR) measurements.…”

Section: Resultsmentioning

confidence: 99%

Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on reactant adsorption at vanadium oxide substrate

Gruber

Hermann

2013

The Journal of Chemical Physics

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Extended cluster models together with density-functional theory are used to evaluate geometric, energetic, and electronic properties of different adsorbate species that can occur at a vanadium oxide surface where the selective catalytic reduction (SCR) of NO in the presence of ammonia proceeds. Here, we focus on atomic hydrogen, nitrogen, and oxygen, as well as molecular NO and NHx, x = 1, 4, adsorption at a model V2O5(010) surface. Binding sites, oxygen and vanadium, at both the perfect and reduced surface are considered where reduction is modeled by (sub-) surface oxygen vacancies. The reactants are found to bind overall more strongly at oxygen vacancy sites of the reduced surface where they stabilize in positions formerly occupied by the oxygen (substitutional adsorption) compared with weaker binding at the perfect surface. In particular, ammonia, which interacts only weakly with vanadium at the perfect surface, binds quite strongly near surface oxygen vacancies. In contrast, surface binding of the NH4 adsorbate species differs only little between the perfect and the reduced surface which is explained by the dominantly electrostatic nature of the adsorbate interaction. The theoretical results are consistent with experimental findings and confirm the importance of surface reduction for the reactant adsorption forming elementary steps of the SCR process.

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“…The corresponding experimental values are reported to be in the range 46-75 kJ mol -1 [51], and probably having a large contribution from water that is loosely bonded to surface hydroxyl groups. The binding energy of crotonaldehyde is estimated to be fairly high, ΔE = -82.93 kJ mol -1 , which is in qualitative agreement with the temperature programmed desorption (TPD) study by Raskó and Kiss which showed no substantial crotonaldehyde and water desorption below a substrate temperature of 473 K [48].…”

Section: Figure 11mentioning

confidence: 97%

Acetaldehyde adsorption and condensation on anatase TiO2: Influence of acetaldehyde dimerization

Stefanov

Topalian

Granqvist

et al. 2014

Journal of Molecular Catalysis A: Chemical

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Conversion of acetaldehyde to crotonaldehyde on anatase TiO 2 films was studied by in situ Fourier transform infrared spectroscopy (FTIR) and by density functional theory (DFT) calculations. In situ FTIR showed that acetaldehyde adsorption is accompanied by the appearance of a hitherto nonassigned absorption band at 1643 cm -1 , which is shown to be due to acetaldehyde dimers. The results were supported by DFT calculations. Vibrational frequencies calculated within a partially relaxed cluster model for molecular acetaldehyde and its dimer, and for the corresponding adsorbed species on the anatase (101) surface, were in good agreement with experimental results. A kinetic model was constructed based on the combined FTIR and DFT results, and was shown to explain the essential features of the acetaldehyde condensation reaction.

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Temperature-programmed desorption/reaction and in situ spectroscopic studies of vanadia/titania for catalytic reduction of nitric oxide

Cited by 120 publications

References 34 publications

VANADIUM‐TITANIUM OXIDE CATALYSTS. INFLUENCE OF THE PREPARATION METHOD ON THE o‐XYLENE SELECTIVE OXIDATION

VANADIUM‐TITANIUM OXIDE CATALYSTS. INFLUENCE OF THE PREPARATION METHOD ON THE o‐XYLENE SELECTIVE OXIDATION

Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on reactant adsorption at vanadium oxide substrate

Acetaldehyde adsorption and condensation on anatase TiO2: Influence of acetaldehyde dimerization

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