Selective catalytic reduction of nitric oxide with ammonia

Baiker, Alfons; Dollenmeier, P.; Gliński, Marek; Reller, Armin

doi:10.1016/s0166-9834(00)82872-9

Cited by 158 publications

(67 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reduction of amorphous bulk V 2 O 5 takes place at about 70-80 K higher than that observed in the case of the monomeric species. Thus with an increase coverage of titania by vanadia and vanadia polymerization degree, the TPR peak should shift to higher temperatures in accordance with the literature data (27)(28)(29). This trend, however, cannot be extended to vanadia on other supports because of the change in the vanadiasupport interaction dependent on the electronegativity of the support cation (8,11).…”

Section: Reducibility Of Surface Vanadia Species By Hydrogensupporting

confidence: 84%

Characterization of Surface Vanadia Forms on V/Ti–Oxide Catalyst via Temperature-Programmed Reduction in Hydrogen and Spectroscopic Methods

Bulushev

Kiwi‐Minsker

Rainone

et al. 2002

Journal of Catalysis

100

View full text Add to dashboard Cite

Surface vanadia species formed on vanadia/titania catalysts consisting of 0.2-2.6 monolayers (ML) of VO x have been characterized by FT-Raman spectroscopy under controlled atmosphere, temperature-programmed reduction in hydrogen (TPR), and solubility in diluted HNO 3 . Three types of species were observed with the maximum peak temperatures as follows: isolated monomeric species (≤770-780 K), polymeric species (810 K), and bulk amorphous V 2 O 5 (852 K). During the reduction, the V= =O bond of the monomeric species with tetracoordinated vanadium disappears as shown by diffuse reflectance infrared Fourier transform spectroscopy. A formation of new hydroxyl groups with a basic character was observed. The monomeric species was found to be chemically stable with respect to diluted HNO 3 . Bulk amorphous V 2 O 5 and polymeric vanadia were soluble in HNO 3 and removed from the surface. The state of vanadium in the oxidized catalysts was mainly pentavalent, as shown by XPS, and did not change after acid treatment. Reduction by hydrogen of monolayer vanadia in a 0.2-ML V/TiO 2 catalyst was studied by temperature-programmed reduction (TPR) at different heating rates. A one-site kinetic model is able to account for the TPR data, in spite of the presence of the monomeric and polymeric species. This indicates that these species could be considered equal with respect to the interaction with hydrogen. The activation energy was determined for the catalyst reduction (98 ± 5 kJ/mol).

show abstract

Section: Reducibility Of Surface Vanadia Species By Hydrogensupporting

confidence: 84%

Characterization of Surface Vanadia Forms on V/Ti–Oxide Catalyst via Temperature-Programmed Reduction in Hydrogen and Spectroscopic Methods

Bulushev

Kiwi‐Minsker

Rainone

et al. 2002

Journal of Catalysis

100

View full text Add to dashboard Cite

show abstract

“…4) reflect the reducibility of vanadia species in hydrogen. Thus, with an increase of vanadia coverage, the maximum of the TPR peak shifts to higher temperatures in line with the literature data [8,18,23,24]. The insoluble monomeric species are the species easily reducible by hydrogen (T max 770-780 K) (Fig.…”

Section: Vanadia/titania Catalysts Prepared By Impregnation and Graftingsupporting

confidence: 90%

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

2004

View full text Add to dashboard Cite

Pure and K-doped vanadia/titania prepared by different methods have been studied in order to elucidate the role of vanadia species (monomeric, polymeric, bulk) in catalytic toluene partial oxidation. The ratio of different vanadia species was controlled by treating the catalysts in diluted HNO 3 , which removes bulk vanadia and polymeric vanadia species, but not the monomeric ones, as was shown by FTRaman spectroscopy and TPR in H 2 . Monolayer vanadia species (monomeric and polymeric) are responsible for the catalytic activity and selectivity to benzaldehyde and benzoic acid independently on the catalyst preparation method. Bulk V 2 O 5 and TiO 2 are considerably less active. Therefore, an increase of the vanadium concentration in the samples above the monolayer coverage results in a decrease of the specific rate in toluene oxidation due to the partial blockage of active monolayer species by bulk crystalline V 2 O 5 . Potassium diminishes the catalyst acidity resulting in a decrease of the total rate of toluene oxidation and suppression of deactivation. Deactivation due to coking is probably related to the Brønsted acid sites associated with the bridging oxygen in the polymeric species and bulk V 2 O 5 . Doping by K diminishes the amount of active monolayer vanadia leading to the formation of non-active K-doped monomeric vanadia species and KVO 3 . # 2004 Elsevier B.V. All rights reserved.

show abstract

“…J, Thermal Anal., 38, 1992 TURCO et al: THERMAL BEHAVIOUR 2633 Morishige [12] reported that TiO2 as anatase phase undergoses removal of most OH surface groups in a temperature range extending up to 400~ The decreasing of weight loss with vanadium content can be explained by supposing that the surface OH groups of TiO~ are involved in the interaction with vanadium species, as suggested by Baiker [13]. A further weight loss, absent for pure TiO2, is observed at temperature between 650 ~ and 700~ in TG curves of all V2Os/TiO2 catalysts.…”

Section: Resultsmentioning

confidence: 99%

Thermal behaviour of high surface area V2O5/TiO2 catalysts

Turco

Bagnasco

Lisi

et al. 1992

Journal of Thermal Analysis

View full text Add to dashboard Cite

Thermal analysis (TG and DTA) was employed for the characterization of V2Os/TiO2 catalysts supported on high surface urea TiO2. The results obtained are consistent with a uniform spreading of vanadium oxide on TiO2 surface for V205 content less than 15% by weight.The presence of V205 on the surface of TiO2 affects the anatase-rutile phase transition lowering the temperature at which it occurs.DTA measurements, performed on catalysts after many months from the preparation, show the appearance of an exothermic peak in the range 2g0~176This signal has been related to the oxidation of V(IV) to V(V) on the catalyst surface.Catalysts characterization, performed by chemical analysis and FT-IR spectroscopy, has confirmed this interpretation.It has been suggested that a slow modification of the catalyst occurs, leading to an increase of the V(IV) content during the time. The nature of vanadium oxide species constituting the monolayer has been investigated by different techniques [4][5][6][7]. However thermal analysis was scarcely employed to characterize the V2Os/TiO2 systems [8,9].In a recent work [10] we have studied chemical and physical properties of high surface area V2Os/TiO2 catalysts prepared by supporting V205 on laser synthesized ultrafine TiO2 powders. In this work we have employed the DTA and TG techniques in order to study the thermal stability of V2Os/TiO2 catalysts. Moreover, by such techniques, a further contribution to the characterization of vanadium oxide species formed on the catalyst surface has been achieved. ExperimentalThe V2Os/TiO2 catalysts were obtained by impregnation with NH4VO3 solution of high surface area (128 m2/g) TiO2 powder. The TiO2 support was synthesized by laser pyrolysis technique, as described in [11]. The catalysts were dried in oven at 120~ and then calcined at 400~ in air flow (99.95% purity) for 3 h. The catalysts contained V20~ nominal contents of 4, 8 and 15 wt%.The chemical analysis of V(IV) and V(V) was effected dissolving the catalysts in concentrated H2504 and titrating with KMnO4 to determine V(IV) content. The vanadium was reduced to +4 oxidation state with Fe(NHa)2(SO4)2.6H20 and then titrated with KMnO4 again to determine the total vanadium content.Thermal analysis was effected by using a DuPont 9000 system constituted by TG and DTA independent units. Both TG and DTA measurements were effected with heating rate of 20 deg/min. The reference for DTA measurements was TiO2 calcined at 1000~ which did not show any thermal effect in the whole range of temperature investigated.IR measurements were effected on a IFS 66 Bruker FT-IR apparatus using the KBr pellets technique. Results and discussionThe results were obtained on samples as synthesized and after different times from the synthesis.The results of chemical analysis of catalysts are reported in Table 1 as total vanadium and V(IV) content.The TG curves for pure TiO2 and for the catalysts after 1.5 years from the synthesis are shown in Fig. 1. It can be observed a large weight loss for all samples that starts at room te...

show abstract

Selective catalytic reduction of nitric oxide with ammonia

Cited by 158 publications

References 17 publications

Characterization of Surface Vanadia Forms on V/Ti–Oxide Catalyst via Temperature-Programmed Reduction in Hydrogen and Spectroscopic Methods

Characterization of Surface Vanadia Forms on V/Ti–Oxide Catalyst via Temperature-Programmed Reduction in Hydrogen and Spectroscopic Methods

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

Thermal behaviour of high surface area V2O5/TiO2 catalysts

Contact Info

Product

Resources

About