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Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
41092 45877 2012 9 PDF Available
Title
Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts
Abstract

Mono- and bi-component cobalt and manganese samples were prepared by impregnation of silica with aqueous solutions of Co(NO3)2·6H2O and/or Mn(NO3)2·6H2O. The bi-component samples were obtained by a common solution of Co- and Mn nitrates (CoMn-MS) or by deposition of cobalt on calcined Mn sample (Co + Mn). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction (TPR), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis and tested in reaction of complete n-hexane oxidation. It was observed that the well crystalline cobalt oxide partially covers poorly crystalline manganese oxide in the Co + Mn catalysts, while finely divided oxides (MnO2 and Mn2O3, Co3O4) are present on the surface of the (CoMn-MS) sample. Four Langmuir–Hinshelwood and two Mars–van Krevelen models were fitted with the experimental data from the catalytic tests. According to the model calculations and results from instrumental methods, the reaction pathway over single component manganese and bi-component Co-Mn catalysts proceeds through Mars–van Krevelen mechanism (the oxidation of the catalyst surface being the rate determining step), while Langmuir–Hinshelwood mechanism is more probable for the Co sample. A considerable increase in activity for the sample obtained from a mixed solution is explained by low crystallinity, simultaneous presence of Mn4+–Mn3+ and enrichment of the surface in oxygen species.

Graphical abstract.Figure optionsDownload full-size imageDownload high-quality image (210 K)Download as PowerPoint slideHighlights► Oxi-redox (Mars–van Krevelen) mechanism on the single manganese sample. ► Associative (Langmuir–Hinshelwood) mechanism is more probable for Co sample. ► Mars–van Krevelen predominates on CoMn bi-component catalysts. ► The highest activity of the catalyst prepared from a mixed solution Co(NO3)2 and Mn(NO3)2.

Keywords
n-Hexane complete oxidation; Kinetics models; Supported Co-Mn oxide catalysts
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Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 413–414, 31 January 2012, Pages 43–51
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