Kinetic peculiarities of the simplest reactions in solids

✍ Scribed by V.A. Tolkatchev

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 393 KB
• Volume: 86
• Category: Article
• ISSN: 0167-7322
• DOI: 10.1016/s0167-7322(99)00122-1

✦ Synopsis

Two extreme cases of the formal kinetic description are discussed. One of them is the rate constant distribution. In this case it is assumed that reagent in solids may be divided into subensembles. Each subensemble reacts according to simple kinetic law and the overall kinetics is a sum of the individual ones. The second case corresponds to a uniformly proceeding reaction. However, its rate constant k(t) varies with time. The criterion has been formulated which allows one to discriminate between kinetic models.

The example of the reaction where the time-dependent k(O takes place will be discussed in detail. It is the case of oxidation of alkyl and matrix radical by diffusing oxygen in methanol glass at 77-90 K. Time dependence of k(t) is compared with the diffusion coefficient time-dependence. It is concluded that both the slowing down of oxygen migration due to matrix relaxation and the local relaxation process in the vicinity of radical lead to a decrease in oxidation rate constants.