Mechanism of the Low-Temperature Interaction of Hydrogen with a-Oxygen on FeZSM-5 Zeolite Full article
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Kinetics and Catalysis
ISSN: 0023-1584 , E-ISSN: 1608-3210 |
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| Output data | Year: 2004, Volume: 45, Number: 2, Pages: 202-208 Pages count : 7 DOI: 10.1023/B:KICA.0000023792.95153.d8 | ||
| Tags | Activation Energy; Zeolite; Radical Anion; Bond Energy; Isotope Effect | ||
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Abstract:
The mechanism of a low-temperature reaction of hydrogen with the radical anion surface oxygen species (α-oxygen, Oα) formed by decomposing N2O over FeZSM-5 zeolite was studied using kinetic and isotope techniques. It was found that the reaction is of first order with respect to hydrogen and the rate of the reaction is proportional to the concentration of Oα. The activation energy of the reaction, which was measured for H2 or D2 over a temperature range from +20 to -100°C, is equal to 3.2 or 5.3 kcal/mol, respectively. The reaction occurs with a considerable kinetic isotope effect (kH/k D), which varies over the range of 3.4-41 depending on the temperature. This fact indicates that the rate-limiting step of the reaction includes the dissociation of the hydrogen molecule. The temperature dependence of the isotope effect gave a value of 2.1 kcal/mol, which is close to the difference between the zero bond energies in the molecules of H2 and D2; this fact suggests that a tunnel effect does not significantly contribute to the reaction. The dissociative mechanism is consistent with data obtained by in situ IR spectroscopy. The interaction of hydrogen with α-oxygen is accompanied by the formation of new hydroxyl groups O αH (absorption bands at 3635 and 3674 cm-1) at the surface of the zeolite. The identification of these groups was supported by an isotope shift either on the replacement of H2 by D2 or on the replacement of 16Oα by Oα,. The stoichiometric ratio H2:Oα, is consistent with the previously drawn conclusion on the paired arrangement of α-sites.
Cite:
Dubkov K.A.
, Starokonʹ E.V.
, Paukshtis E.A.
, Volodin A.M.
, Panov G.I.
Mechanism of the Low-Temperature Interaction of Hydrogen with a-Oxygen on FeZSM-5 Zeolite
Kinetics and Catalysis. 2004. V.45. N2. P.202-208. DOI: 10.1023/B:KICA.0000023792.95153.d8 WOS Scopus РИНЦ ANCAN OpenAlex
Mechanism of the Low-Temperature Interaction of Hydrogen with a-Oxygen on FeZSM-5 Zeolite
Kinetics and Catalysis. 2004. V.45. N2. P.202-208. DOI: 10.1023/B:KICA.0000023792.95153.d8 WOS Scopus РИНЦ ANCAN OpenAlex
Original:
Дубков К.А.
, Староконь Е.В.
, Паукштис Е.А.
, Володин А.М.
, Панов Г.И.
Механизм низкотемпературного взаимодействия водорода с а-кислородом на цеолите FeZSM-5
Кинетика и катализ. 2004. Т.45. №2. С.218-224. РИНЦ
Механизм низкотемпературного взаимодействия водорода с а-кислородом на цеолите FeZSM-5
Кинетика и катализ. 2004. Т.45. №2. С.218-224. РИНЦ
Dates:
| Submitted: | Oct 9, 2002 |
| Published print: | Mar 1, 2004 |
Identifiers:
| Web of science: | WOS:000221291000007 |
| Scopus: | 2-s2.0-3543078682 |
| Elibrary: | 13470087 |
| Chemical Abstracts: | 2004:304518 |
| Chemical Abstracts (print): | 140:363712 |
| OpenAlex: | W2045717451 |