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Autonomous and forced oscillations during methane oxidation over cobalt catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
43715 45984 2007 10 PDF Available
Title
Autonomous and forced oscillations during methane oxidation over cobalt catalysts
Abstract

Oscillatory behaviour during methane oxidation over a cobalt foil has been studied using on-line mass-spectrometry and video recording of the colour of the catalyst surface. It was demonstrated that during oscillatory behaviour, periodic transitions of the catalyst surface from an oxidised state (dark colour) to a reduced state (light colour) occurred together with the variation of the catalyst temperature. Oscillations over the cobalt foil appeared at higher temperatures (860–950 °C), and had longer periods, in comparison with oscillatory behaviour which was observed earlier over a nickel foil. The application of TGA in combination with TPR experiments revealed the differences in nickel and cobalt redox properties which are responsible for the variation in the properties of the oscillations. Forced oscillations could be obtained in a low temperature region (700–860 °C), if bare chromel and alumel wires were spot-welded separately to the cobalt foil. It was shown that in this case the chromel wire induced oscillatory behaviour of the whole cobalt foil. Complicated mixed mode oscillations detected at higher temperatures were shown to be the result of the coupling of high frequency oscillations produced by the unshielded chromel–alumel thermocouple and low frequency oscillations appearing over the cobalt foil.

Graphical abstractOscillatory behaviour during methane oxidation over a Co foil has been studied using on-line mass-spectrometry and video recording of the colour of the catalyst surface. It was demonstrated that during oscillatory behaviour, periodic transitions of the catalyst surface from an oxidised state (dark colour) to a reduced state (light colour) occurred together with the variation of the catalyst temperature. Oscillations over the Co foil appeared at higher temperatures (860–950 °C), and had longer periods, in comparison with oscillatory behaviour which was observed earlier over a nickel foil. The application of TGA in combination with TPR experiments revealed the differences in nickel and cobalt redox properties which are responsible for the variation in the properties of the oscillations. Forced oscillations could be obtained in a low temperature region (700–860 °C), if bare chromel and alumel wires were spot-welded separately to the cobalt foil. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Oscillations; Forced oscillations; Methane oxidation; Cobalt catalysts; Nickel catalysts; Synchronization
First Page Preview
Autonomous and forced oscillations during methane oxidation over cobalt catalysts
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 321, Issue 2, 11 April 2007, Pages 180–189
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis