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The catalytic reactions of n-pentane and 1-pentene on different molybdenum oxides and metal surfaces

Paper ID Volume ID Publish Year Pages File Format Full-Text
43772 45987 2008 8 PDF Available
Title
The catalytic reactions of n-pentane and 1-pentene on different molybdenum oxides and metal surfaces
Abstract

Catalytic reactions of n-pentane and 1-pentene were performed as a function of reaction temperature, on different molybdenum oxides and metal surfaces. These oxides such as Mo2O5 and MoO2 were obtained following the exposure of MoO3/TiO2 to hydrogen at different temperatures up to 673 K. Metallic Mo(0) state is obtained at reduction temperatures beyond 723 K. Identification of the Mo chemical species was performed using in situ XPS-UPS surface techniques. The combination of both techniques provides valuable information on the chemical composition of the upper 10 atomic monolayers. X-ray diffraction and HRTEM techniques were also employed. The reduction procedure of MoO3 does not follow the same pathway when it is deposited on an Al2O3 support. A strong electronic interaction between the two species promotes the formation of an Al2(MoO4)3 complex as revealed by XRD measurements. Catalytic active functions present on the different Mo species surfaces are of the acidic type (Lewis and Brönsted) on Mo2O5, metal-acid (bifunctional) on MoO2 and metal function on metallic Mo(0). Consequently, a specific catalytic reaction of n-pentane, such as hydroisomerization to iso-pentane, which is rationalized in terms of a bifunctional mechanism, is expected to occur on MoO2. Different isomerization reactions of 1-pentene were obtained in the case of MoO3/TiO2 and MoO3/Al2O3 at reduction temperatures below 573 K. However, in the case of Mo on the alumina support, the conversion of 1-pentene to iso-pentane is low and irreproducible, contrary to what has been observed for Mo on titania.

Graphical abstractHydrogen exposure of the equivalent 5 monolayers of MoO3 deposited on TiO2 as a function of temperature up 873 K, enabled us to partially reduce the molybdenum trioxide on the sample surface to three distinct, Mo2O5, bifunctional MoO2(Hx)ac and metallic Mo(0) states. Catalytic behavior of these phases towards n-pentane and 1-pentene were studied. Figure shows XRD for MoO3/TiO2 after reduction at 653 K. (★) MoO3; () MoO2; () TiO2 anatase; () TiO2 rutile.Figure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
XPS-UPS; XRD; HRTEM; MoO3; MoO2; TiO2; Al2O3; Hydroisomerization of 1-pentene and n-pentane; Iso-pentane
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The catalytic reactions of n-pentane and 1-pentene on different molybdenum oxides and metal surfaces
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 341, Issues 1–2, 15 June 2008, Pages 160–167
Authors
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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