Oxidation of paraffin hydrocarbons in the presence of a homogeneous CrMnK catalyst

Abstract

INDUSTRIAL, liquid-phase oxidation of paraffin hydrocarbons into synthetic aliphatic acids (SAA) is carried out using a manganese-potassium catalyst [I] This catalyst fulfils several functions, particularly catalysis of oxidation, taking part in the decomposition of hydroperoxides. Manganese in the oxidized valency state reacts with ketones, oxidizing them into acids [2] (the role of potassium in a mixed catalyst has been explained previously [3-5]). In oxidation manganese salts have an inhibiting function, ude to the formation of hydroxy-peroxide radicals from secondary alcohols and their breakdown by the reaction with Mn (II) and Mn (III) [6]. To increase the rate and selectivity of oxidation of paraffin to SAA it is necessary on the one hand to increase catalyst concentration. On the other, an increase in concentration may inhibit and stop the process. I t was shown [7] that to obtain acids with a minimum content of ketoand hydroxy acids and polyfunctional acids and lactones, paraffin should be oxidized with a Mn-K catalyst for about 21 hr which, of course, is unacceptable in practice. A shortcoming of the Mn-K catalyst is its rapid precipitation into residue when replacing the initial stearate acid residue by residues of diacids formed in the oxidate [8]. A promising method of intensifying oxidation is the use of a composite catalyst, in which in addition to Mn-K there would be a component, which would break down secondary hydroperoxides chiefly into kctones. This would enable the rate of formation of SAA to be increased without increasing Mn concentration as a consequence of more rapid reactions