Situ and Operando Raman Spectroscopy of Oxidation Catalysts

In Situ and Operando Raman Spectroscopy of Oxidation Catalysts 

Over the past two decades, Raman spectroscopy has been extensively applied during catalytic oxidation reactions by mixed-metal oxides and metals under in situ and operando spectroscopy conditions, which has allowed the direct identification of the catalytic active sites involved in the oxidation reactions. Among the multiple spectroscopic techniques that can provide information about the catalytic active sites under oxidation reaction conditions, Raman spectroscopy is unique because of its ability to directly provide molecular level information that allows discrimination among the different catalytic active sites which may be present in the oxidation catalyst. This chapter provides a snapshot of the types of fundamental information obtainable by Raman spectroscopy, and the different types of catalytic materials and oxidation reactions that have been reported, especially under oxidation reaction conditions. 

Catalytic oxidation represents the major technology employed by the chemical industry to produce and upgrade chemical intermediates (e.g. the oxidation of methanol to formaldehyde, ethylene to ethylene epoxide, -butane to maleic anhydride, o-xylene to phthalic anhydride, etc.), and is also the method of choice for the environmental remediation of toxic emissions (e.g. the oxidation of hydrocarbons, carbon monoxide, H2S to elemental sulfur and SO2, etc.). These oxidative chemical transformations take place at catalytic active sites present in the oxidation catalysts. 

Among the multiple spectroscopic techniques that can provide information about the catalytic active sites under reaction conditions (Raman, IR, UV-vis, X-ray absorption (EXAFS (extended X-ray absorption fine structure)/XANES (X-ray absorption near edge structures)), nuclear magnetic resonance (NMR), electron sprin resonance (ESR), etc.), Raman spectroscopy is the technique of choice because of 

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Another important process in which catalyst deactivation by coke deposits plays an important role is propane dehydrogenation, which can be performed with a variety of materials, including metal and metal oxide catalysts. Different in situ and operando spectroscopies have been applied to these catalysts, including UV-vis, Raman, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopies [4, 115, 140],... 

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