Can someone recommend the most reliable way to estimate the number of active sites of Ru, Co, and Cu catalysts on Al2O3?
1) Of course there isn't a 100% correct way of doing it, that's why I wrote "most reliable" :)
2) In the case of pure metal nanoparticles (e.g. Au) it is easily done from TEM images + crystalline cell of Au. But what about when we start with a metal oxide? E.g. the starting point is CoO/Al2O3. We reduce the catalyst to get "Co"/Al2O3 with H2. But, of course, only the surface of nanoparticles gets reduced, not the bulk. How can TEM help then? Do we have to assume a monolayer of Co covering our nanoparticles, and just calculate the active sites from TEM + atomic radius of Co?
3) Are there any good sorption techniques to get the active sites on all three catalysts correctly?
Thanks in advance
Dear Yury Gorbanev, these type of catalysts are much more used in thé Tropsch-Fischer process. Many conventional characterization techniques are used to titrate reactive sites. Please check the following links. My Regards
https://doi.org/10.1021/cs400381f
https://doi.org/10.1002/anie.201908060
https://doi.org/10.1080/10916460903585972
https://doi.org/10.1021/ja902587k
https://www.researchgate.net/publication/291424383_Methanation_of_carbon_dioxide_on_RuAl2O3_Catalytic_activity_and_infrared_study
https://www.researchgate.net/publication/248191783_XPS_FTIR_and_TPR_characterization_of_RuAl_2O_3_catalysts
Hi;
The determination of the metallic active area of supported metallic catalysts requires a distinction between the area of the metal phase and that of the support. By chemisorption it is possible to have a selective adsorption on the active sites of the metal. Indeed, it is possible to choose a gas chemisorbed by the metal and inert with respect to the support (for example CO). The value of the number of active sites is obtained by experiment or by calculating the crystalline parameters of the metal.
With my best regards
Dear Yury, in our paper, Journal of Catalysis 189, 456–462 (2000), we investigated the reducibility of Co-oxide particles by EXAFS. Co reducibility depend on the cluster size. - Also we studied the Ru-Co system ( Applied Catalysis A: General 242 (2003) 179–186 ). - The presence of noble metal was necessary to reduce Co ions. We have investigated the effect of Pt and Re too.
With my best regards
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