Operando XAS analysis of CuO/SiO2 and CuO/CeO2 catalystsAlbin Pintar
, Maxim Zabilsky
, Petar Djinović
, Janvit Teržan
, Iztok Arčon
, 2018, published scientific conference contribution abstract
Abstract: The possibilities of the operando XAS analysis of catalysts will be presented on two case
studies of promising new catalytic materials: alkali doped nano-dispersed copper oxide
clusters on ordered mesoporous SiO2, which is highly active and selective towards propylene
epoxidation , and nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction .
Operando Cu K-edge and Ce L3-edge XANES and EXAFS analysis was performed during
catalytic reactions under controlled reaction conditions in a tubular reactor filled with
protective He atmosphere at 1 bar. The spectra were measured before the reaction at RT, then
during heating, and during catalytic reaction at 400 °C under controlled atmosphere.
Operando XANES analysis is used to monitor the changes in valence states and local
symmetries of Cu and Ce cations in the catalysts. A partial reduction of Cu2+ to Cu+ and Cu0
and Ce4+ to Ce3+ species was detected during catalyst activation, and re-oxidation during
catalytic reaction. Different dynamics of reaching a quasi-steady oxidation state were revealed
as the tested catalysts approached the quasi-steady state after 300 min of reaction.
Operando EXAFS spectra are used to precisely determine local structure of Cu and Ce
cations, to identify structural characteristics and changes of Cu and Ce species during the
catalytic reactions. In this way, the active site in the catalytic reactions can be identified and
the mechanism of the reaction clarified.
The results of operando XAS analyses are crucial to guide further material modification, to
obtain more effective catalyst, and material which is more resistant to inhibiting effects that
cause catalyst deactivation during catalytic reaction.
Found in: osebi
Keywords: katalizatorji, Cu XANES, EXAFS
Published: 12.09.2018; Views: 1960; Downloads: 0
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