Kinetics of the oxidation of ethane in presence of hydrogen bromide

Abstract

1. A study was made of the kinetic laws of the oxidation of ethane to acetic acid in presence of hydrogen bromide. It was shown that the process of acetic acid formation comes to an end long before the reactants are used up. Such “limit phenomena” are explained on the basis of the existence of an initiating reaction that results in the formation of an intermediate product, the amount of which determines the yield of acetic acid. 2. It was established that, whatever method is adopted for initiating the oxidation process by additions of catalyst (hydrogen bromide), the yield of. acetic acid cannot be raised above 40% on the amount of ethane taken. The generality of the phenomenon was pointed out: it is found in other slow-oxidation reactions. 3. With the aid of a method based on the study of the evolution of heat in the reaction mixture during the reaction it was shown that the mechanism of the reaction includes a sequence of two macroscopic stages displaced from one another in time. The first stage — the initiating reaction — is a homogeneous-heterogeneous process. The second stage — the formation of acetic acid initiated by the decomposition of the intermediate product obtained in the first stage — is a homogeneons process. These results confirm the prevalence of the phenomenon of successive macroscopic stages in oxidation processes initiated by additions of homogeneous catalysts.