Effect of Cs+ Promoter in Ru/MgO Catalysts
The Journal of Physical Chemistry C
, E-ISSN: 1932-7455
Larichev Yurii V.
Boreskov Institute of Catalysis SB RAS
Ru/MgO and Ru−Cs+/MgO catalysts were prepared from Ru(OH)Cl3 and were studied by XPS, TEM, CO chemisorption, and EXAFS. An explanation for the large differences in sizes of Ru particles measured by TEM and XRD compared to those determined by CO chemisorption is proposed. This explanation is based on the XPS data that the initial catalyst Ru/MgO consists of Ru0 metal particles and RuO2 clusters. The latter are not measured by CO chemisorption and have high stability due to RuO2−MgO interaction. A new feature of Cs+ promoter influence on the Ru/MgO catalyst was found. The addition of Cs+ to the Ru/MgO catalyst, which contains Ru partly in the oxidized form, does not lead to the formation of any cesium ruthenates. Instead, the cesium promoter reduces the RuO2 clusters, which are stabilized by epitaxy interaction with the support, to form the Ru0 particles. This new feature of Cs+ promoter results in the increase of supported Ru useful ratio and Ru-specific surface area in these catalysts.