1 research outputs found
Mapping Temperature Heterogeneities during Catalytic CO<sub>2</sub> Methanation with <i>Operando</i> Luminescence Thermometry
Controlling and understanding reaction temperature variations
in
catalytic processes are crucial for assessing the performance of a
catalyst material. Local temperature measurements are challenging,
however. Luminescence thermometry is a promising remote-sensing tool,
but it is cross-sensitive to the optical properties of a sample and
other external parameters. In this work, we measure spatial variations
in the local temperature on the micrometer length scale during carbon
dioxide (CO2) methanation over a TiO2-supported
Ni catalyst and link them to variations in catalytic performance.
We extract local temperatures from the temperature-dependent emission
of Y2O3:Nd3+ particles, which are
mixed with the CO2 methanation catalyst. Scanning, where
a near-infrared laser locally excites the emitting Nd3+ ions, produces a temperature map with a micrometer pixel size. We
first designed the Y2O3:Nd3+ particles
for optimal temperature precision and characterized cross-sensitivity
of the measured signal to parameters other than temperature, such
as light absorption by the blackened sample due to coke deposition
at elevated temperatures. Introducing reaction gases causes a local
temperature increase of the catalyst of on average 6–25 K,
increasing with the reactor set temperature in the range of 550–640
K. Pixel-to-pixel variations in the temperature increase show a standard
deviation of up to 1.5 K, which are attributed to local variations
in the catalytic reaction rate. Mapping and understanding such temperature
variations are crucial for the optimization of overall catalyst performance
on the nano- and macroscopic scale