Theoretical study on the reaction mechanism of NO and CO catalyzed by Rh atom |
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Authors: | Qian-Qian Xu Hua-Qing Yang Chao Gao Chang-Wei Hu |
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Affiliation: | 1. Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, 610064, Sichuan, People’s Republic of China 2. College of Chemical Engineering, Sichuan University, Chengdu, 610065, Sichuan, People’s Republic of China
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Abstract: | The gas-phase reaction mechanism of NO and CO catalyzed by Rh atom has been systematically investigated on the ground and first excited states at CCSD(T)//B3LYP/6-311+G(2d), SDD level. This reaction is mainly divided into two reaction stages, NO deoxygenation to generate N2O and then the deoxygenation of N2O with CO to form N2 and CO2. The crucial reaction step deals with the NO deoxygenation to generate N2O catalyzed by Rh atom, in which the self-deoxygenation of NO reaction pathway is kinetically more preferable than that in the presence of CO. The minimal energy reaction pathway includes the rate-determining step about N–N bond formation. Once the NO deoxygenation with CO catalyzed by rhodium atom takes place, the reaction results in the intermediate RhN. Then, the reaction of RhN with CO is kinetically more favorable than that with NO, while both of them are thermodynamically preferable. These results can qualitatively explain the experimental finding of N2O, NCO, and CN species in the NO + CO reaction. For the N2O deoxygenation with CO catalyzed by rhodium atom, the reaction goes facilely forward, which involves the rate-determining step concerning CO2 formation. CO plays a dominating role in the RhO reduction to regenerate Rh atom. The complexes, OCRhNO, RhON2, RhNNO, ORhN2, RhCO2, RhNCO, and ORhCN, are thermodynamically preferred. Rh atom possesses stronger capability for the N2O deoxygenation than Rh+ cation. |
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