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Understanding the activation mechanism induced by NOx on the performances of VOx/TiO2 based catalysts in the total oxidation of chlorinated VOCs

Paper ID Volume ID Publish Year Pages File Format Full-Text
48818 46522 2007 10 PDF Available
Title
Understanding the activation mechanism induced by NOx on the performances of VOx/TiO2 based catalysts in the total oxidation of chlorinated VOCs
Abstract

A previous investigation of the chlorobenzene combustion activity of VOx/TiO2, VOx–WOx/TiO2 and VOx–MoOx/TiO2 catalysts in the presence of NO pointed out the activation effect of NO. The suggested three-step mechanism based on catalytic performances data only was: (1) chlorobenzene is oxidized on the surface of the VOx phase (as described by Mars–van Krevelen), (2) NO gets oxidized to NO2, mainly on WOx and MoOx, and (3) the in situ produced NO2 assists O2 in the reoxidation of the VOx phase thus speeding up the oxidation step of the Mars–van Krevelen mechanism. The latter effect macroscopically corresponds to the observed increase of chlorobenzene conversion. This contribution aims at validating this hypothetical mechanism by pointing out the favourable occurrence of an oxidation of NO to NO2 on the WOx and MoOx phases and by pointing out the higher efficiency of NO2 than O2 to reoxidize the reduced VOx sites. In addition, the present contribution clearly demonstrates that, in the absence of NO, the chlorobenzene total oxidation occurred following the Mars–van Krevelen mechanism. Moreover, a thorough characterization of the oxidation state of the vanadium proving that the improvement of the catalyst activity brought by the simultaneous presence of NO and O2 is linked to the stronger reoxidation of the VOx active phase. Furthermore, plotting all the catalytic activity data versus the mean vanadium oxidation level clearly depicts, for the first time, the strong dependence between them. Under a mean vanadium oxidation level of 4.82 the catalyst is inactive while above 4.87 the activity is stabilized at a high level of conversion independent of the vanadium oxidation level.

Keywords
Catalytic oxidation; VOC combustion; Dioxins; Chlorinated VOCs; Chlorobenzene; Vanadia/titania catalyst; V/W/Ti; V/Mo/Ti; NOx; Vanadium oxidation state
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Understanding the activation mechanism induced by NOx on the performances of VOx/TiO2 based catalysts in the total oxidation of chlorinated VOCs
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 70, Issues 1–4, 31 January 2007, Pages 360–369
Authors
, , , , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us