Investigation of the state of palladium in the potassium palladium-11-tungstosilicate/alumina system by diffuse-reflectance IR spectroscopy |
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| Authors: | P. A. Korovchenko R. A. Gazarov A. Yu. Stakheev L. M. Kustov |
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| Affiliation: | (1) I. M. Gubkin State University of Oil and Gas, 65 Leninsky prosp., 117917 Moscow, Russian Federation;(2) N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 117913 Moscow, Russian Federation |
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| Abstract: | The influence of redox treatments on the state of palladium in the K6[SiW11PdO39]·11H2O/γ-Al2O3 system was investigated by diffuse-reflectance IR (DRIFT) spectroscopy using CO as a probe molecule. The K6[SiW11PdO39]·11H2O heteropoly-compound (HPC) and starting γ-Al2O3 support were studied for comparison. It was shown that palladium is present in HPC mainly in the form of Pd2+ ions. Treatment of HPC in an H2 flow results in complete reduction of palladium to Pd0. The HPC is unstable in redox cycles at temperatures above 373 K. When the HPC was supported on alumina, the Keggin units were stabilized on the support surface and Pd+ formed in the oxidized sample. The supported K6[SiW11PdO39]·11H2O/γ-Al2O3 catalyst displays higher thermal stability and does not decompose during redox treatments at temperatures up to 723 K. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 7, pp. 1271–1275. July, 1999. |
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| Keywords: | heteropolycompound heteropolyanion Keggin unit palladium Heteroatom, redox cycle thermal stability diffuse-reflectance FTIR spectroscopy carbon monoxide probe molecules |
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