An IR study of NO adsorption on a CrOx/ZrO2 catalyst |
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| Institution: | 1. School of Resources and Civil Engineering, Northeastern University, Shenyang, Liaoning, China;2. Department of Fire Protection & Safety, Oklahoma State University, Stillwater, OK, USA;3. Department of Chemical Engineering, Oklahoma State University, Stillwater, OK, USA;1. Center for Applied Energy Research, University of Kentucky, Lexington, KY, 40511, USA;2. College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, PR China;3. Department of Chemistry, University of Kentucky, KY, 40506, USA;4. Chemical Engineering Department, Ford Motor Company, 2101 Village Road, Dearborn, MI 48121, USA;5. Department of Inorganic Chemistry, University of Alicante, Ap. 99, 03080 Alicante, Spain;6. Luxfer MEL Technologies, Manchester M27 8LN, United Kingdom;1. State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China;2. University of Chinese Academy of Sciences, Beijing 100049, PR China |
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| Abstract: | The adsorption of NO at room temperature (RT) on a CrOx/ZrO2 catalyst has been investigated by IR spectroscopy and compared with data previously obtained by ESR spectroscopy and chemical titrations. Prior to NO adsorption, the sample was heated in O2 at 923 K (average oxidation number of chromium, ñ = 5.5) and reduced in CO from 373 to 623 K (ñ varying from 5.5 to 2.5). The adsorption of NO on samples heated in O2 yields mainly dinitrosyls of CrIII, arising from the reduction of CrV. The adsorption of NO on samples reduced at 373 K yields mainly dinitrosyls of CrIII, in addition to N2O, nitrites and nitrates. The admission of NO on fully reduced samples (ñ = 2.5) yields dinitrosyls of CrIII and mono- and dinitrosyls of CrII, in addition to N2O, nitrites and nitrates. Upon evacuation of the latter sample at 423 K, the adsorbed NO oxidized most of the CrII to CrVI (ñ = 4.2) and, in fact, the nitrosyls of CrIII are the only species detected by IR on NO readmission after evacuation treatment, in addition to N2Oads, nitrites and nitrates. Blank experiments on pure ZrO2 show that the dismutation of NO leading to N2O and nitrites (or nitrates) takes place on sites of the ZrO2 support. When a fully reduced sample is further reacted with water at 853 K, mainly dinitrosyls and mononitrosyls of CrIII are detected upon exposure to NO, since reaction with water selectively oxidized CrII to chromia-like species. |
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