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X-ray spectroscopy

XAFS study of dispersed Pd catalytic nanosystem stabilized on oxide support

Speakers

  • Dr. Vladimir KRIVENTSOV

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Co-authors

Content

It is well-known fact that Pd catalytic systems are very promising for processes of oil refining and petrochemistry. A direct structural XRD study of such systems is difficult due to methodological limitations, while the use of XAFS spectroscopy can provide the necessary data. The first results of the XAFS study of low-percentage Pd catalytic nanosystem stabilized on oxide support are shown. Synthesis of catalysts was carried out by chemisorption impregnation of supports with palladium acetylacetonate from benzene. The impregnation temperature was 20C. The content of palladium in the catalysts was 0.5 wt.%. Before the tests, the samples were subjected to a preliminary oxidation-reduction treatment at 400C. All XAFS (XANES/EXAFS) spectra of the Pd-K edge were recorded at Siberian Synchrotron and Terahertz Radiation Center (SSTRC, Novosibirsk). The study of the state and local structure of the active component were carried out. It was shown that, depending on the prehistory, the formation of different (metals, metal-oxides, oxides) nanosized forms of Pd, which are located on the surface of the supports. The interatomic distances and corresponded coordination numbers were established. All possible structural models were discussed. Additionally, the samples of catalysts were characterized by the HRTEM, EDX, XPS methods. The data obtained by all the methods are in a good agreement. The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University. Vladimir Kriventsov thanks to the Russian Foundation for Basic Research for support of the analysis of the XANES (projects No. 16-03-01139, 17-33-50198, 18-03-01251).