Mechanism of the effect of boric acid on liquid-phase oxidation of paraffin hydrocarbons

Abstract

OXIDATION of paraffin hydrocarbons in the presence of boric acid forms the basis of the industrial production of higher aliphatic alcohols [1]. The use of boric acid improves process selectivity and increases alcohol yield. The alcohols obtained during oxidation are basically secondary alcohols with a statistical distribution of the functional group along the chain, retaining the structure of the initial hydrocarbon [2, 3, 4]. According to present views, dltring the reaction boric acid interacts with alcohols to form compounds, borates, which are less reactive to oxidation, thus preventing any further possible oxidation of alcohols [5, 6]. Further information has recent ly been obtained of the effect on oxidation of boric oxide [5, 7], boric acid esters [5], of the effect of certain boron ecrupounds on the accumulation and decomposition of alkylhydroperoxide [7, 8]; the inhibiting effect on oxidation of some of them was established [5, 9, 10]. The results of these investigations indieate that the effect of compounds containing boron is not restricted to protective functions in relation to alcohols. Apparently, during the oxidation of hydrocarbons in the presence of the above compounds the rates of elementary stages may vary, new directions of reaction be formed, particularly with radicals [7, 11] or intermediate compounds [7, 8] responsible for the chain process of oxidation. The s tudy of the mechanism of action of compounds containing boron, in the oxidation of hydrocarbons is of considerable interest. This paper reports the continuation of earlier investigations into oxidative conversions of aliphatic hydrocarbons and gives the results of a kinetic s tudy of the oxidation of paraffins in the presence of boric oxide.