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Reducing Oxidation Rate with Increasing Oxygen Concentration above Certain Level — Kinetic Explanation for Free-Radical Nonbranched-Chain Processesстатья
- Автор: Silaev Michael M.
- Журнал: International Journal of Scientific Research in Chemistry (IJSRCH)
- Том: 5
- Номер: 4
- Год издания: 2020
- Первая страница: 7
- Последняя страница: 23
- Номер статьи: 20532
- Аннотация: The reaction scheme proposed for the initiated nonbranched-chain addition of free radicals to the multiple bond of the molecular oxygen includes the addition reaction of the peroxyl free radical to the oxygen molecule to form the tetraoxyl free radical. This reaction competes with chain propagation reactions through a reactive free radical. The chain evolution stage in this scheme involves a few of free radicals, one of which (tetraoxyl) is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested scheme rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. The kinetic description with use the obtained rate equations is applied to the γ-induced nonbranched-chain processes of the free-radical oxidation of liquid o-xylene at 373 K and hydrogen dissolved in water containing different amounts of dioxygen at 296 K. The ratios of rate constants of competing reactions and rate constants of addition reactions to the molecular oxygen are defined. In these processes the oxygen with the increase of its concentration begins to act as an oxidation autoinhibitor (or an antioxidant), and the rate of peroxide formation as a function of the dissolved oxygen concentration has a maximum. It is shown that a maximum in these curves arises from the competition between hydrocarbon (or hydrogen) molecules and dioxygen for reacting with the emerging peroxyl 1:1 adduct radical. From the energetic standpoint possible nonchain pathways of the free-radical oxidation of hydrogen and the routes of ozone decay via the reaction with the hydroxyl free radical in the upper atmosphere (including the addition yielding the hydrotetraoxyl free radical, which can be an intermediate in the sequence of conversions of biologically hazardous UV radiation energy) were examined. The energetics of the key radical-molecule gas-phase reactions is considered.Keywords: Low-reactive Radical, Autoinhibitor, Competition, Thermochemical Data, Hydrogen, Energy.
- Добавил в систему: Силаев Михаил Михайлович
Прикрепленные файлы
| № | Имя | Описание | Имя файла | Размер | Добавлен |
|---|---|---|---|---|---|
| 1. | Полный текст | The Kinetic Explanation of Reducing Oxidation Rate with Increasing Oxygen Concentration above the Certain Level for Free-Radical Nonbranched-Chain Processes | M.M._Silaev_IJSRCH_2020_54_7-23.pdf | 626,4 КБ | 12 августа 2020 [SilaevMM] |