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Issue 20, 2006
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Dealing with a local heating effect when measuring catalytic solids in a reactor with Raman spectroscopy

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Abstract

In continuation of our previous work on the applicability of the G(R) correction factor for the quantification of Raman spectra of coke during propane dehydrogenation experiments (Phys. Chem. Chem. Phys., 2005, 7, 211), research has been carried out on the potential of this correction factor for the quantification of supported metal oxides during reduction experiments. For this purpose, supported chromium oxide catalysts have been studied by combined in situ Raman and UV-Vis spectroscopy during temperature programmed reduction experiments with hydrogen as reducing agent. The goal was to quantify on-line the amount of Cr6+ in a reactor based on the measured in situ Raman spectra. During these experiments, a significant temperature effect was observed, which has been investigated in more detail with a thermal imaging technique. The results revealed a temperature ‘on the spot’ that can exceed 100 °C. It implies that Raman spectroscopy can have a considerable effect on the local reaction conditions and explains observed inconsistencies between the in situ UV-Vis and Raman data. In order to minimize this heating effect, reduction of the laser power, mathematical matching of the spectroscopic data, a different cell design and a change in reaction conditions has been evaluated. It is demonstrated that increasing the reactor temperature is the most feasible method to solve the heating problem. Next, it allows the application of in situ Raman spectroscopy in a reliable quantitative way without the need of an internal standard.

Graphical abstract: Dealing with a local heating effect when measuring catalytic solids in a reactor with Raman spectroscopy

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Article information


Submitted
15 Feb 2006
Accepted
04 Apr 2006
First published
19 Apr 2006

Phys. Chem. Chem. Phys., 2006,8, 2413-2420
Article type
Paper

Dealing with a local heating effect when measuring catalytic solids in a reactor with Raman spectroscopy

S. J. Tinnemans, M. H. F. Kox, M. W. Sletering, T. A. (. Nijhuis, T. Visser and B. M. Weckhuysen, Phys. Chem. Chem. Phys., 2006, 8, 2413
DOI: 10.1039/B602311H

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