10.1002/anie.202004778
Angewandte Chemie International Edition
successful because melting and redox reactions occur in the
same temperature window (Figures 2 and 3).
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Our experiments clearly show that MnWO4 is a product of
catalyst deactivation, which is formed under strongly reducing
reaction conditions. However, regeneration by increasing the
partial pressure of oxygen in the feed again is possible
(Figures 4D and Supporting Information, Figure S21).
The study in this report is an example for how in situ and
operando Raman spectroscopy techniques can be applied as
effective, non-invasive tools to obtain valuable information on
high-temperature
catalysts
under
relevant
operation
conditions. Based on experimental evidence, it is clearly
explained how the chemical complexity of the Mn-
Na2WO4/SiO2 catalyst warrants a high yield of C2 products and
long-term stability in the oxidative coupling of methane.
Acknowledgments
Our sincere gratitude goes to Ulla Simon (TU Berlin) for
synthesizing the Mn-Na2WO4/SiO2 catalyst that was used in
this study. We would also like to thank Wiebke Frandsen, Dr.
Thomas Lunkenbein, Dr. Milivoj Plodinec, Jasmin Allan, Dr.
Andrey Tarasov, Dr. Olaf Timpe, Maike Hashagen, Dr. Pierre
Kube, Dr. Hamideh Ahi and Sven Richter for their technical
assistance and scientific discussions. Finally, we would like to
extend our appreciation towards Dr. Rupert Hochleitner of the
Mineralogische Staatssammlung München as well as the
Naturkundemuseum Berlin for providing specimens of natural
braunite (Mn7SiO12).
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