Kinetic analysis of reduction process of supported Rh/Al₂O₃ catalysts by time resolved in-situ UV-vis spectroscopy

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• 作者：Qiang Lin^a ; Ken-ichi Shimizu^b ; Atsushi Satsuma^a ; ^{satsuma@apchem.nagoya-u.ac.jp}
• 关键词：Rhodium ; Deactivation ; Reduction ; In-situ UV&ndash ; vis ; Kinetic analysis
• 刊名：Applied Catalysis A ; General
• 出版年：2012
• 期刊代码：4_0926860x
• 类别：ch
• 出版时间：29 March, 2012
• 卷：419-420
• 期：Complete
• 页码：142-147
• 文件大小：654 K

摘要

Kinetic analysis of reduction of Rh/Al₂O₃ with low Rh-loadings (0.01-0.1 wt%) has been carried out by time resolved in-situ UV-vis spectroscopy. Based on XAFS and UV-vis spectra, it was indicated that Rh was present as surface isolated Rh³⁺ on catalyst calcined at 773 K in air. The rate of reduction of Rh³⁺ to metallic Rh⁰ was determined by in-situ UV-vis measurements under a flow of 1%H₂/He at 523-823 K. The reduction rate increased with Rh-loading but decreased as the calcination temperature elevated. The decrease of metallic Rh⁰ formation with the calcination temperature was in harmony with the reaction rate of CO oxidation. The apparent activation energy (E_a) for the reduction of Rh³⁺ to Rh⁰ was found to be constant around 60-62 kJ mol^鈭? and independent of the calcination temperature and the Rh-loading, indicating the equivalent intrinsic activity of supported Rh species on Rh/Al₂O₃ with the low Rh-loadings.