Process for oxidizing hydrocarbons

In a process for oxidizing hydrocarbons wherein

• a. saturated C.sub.4 -C.sub.20 hydrocarbons are reacted with a gas comprising molecular oxygen in the presence of a boron compound forming esters with alcohols formed from said hydrocarbons;
• b. the resulting reaction mixture containing at least one boric acid ester is hydrolyzed;
• c. the hydrolyzate is separated into a substantially organic component, from which the oxidation product is recovered, and into a substantially aqueous component, containing boric acid and water-soluble organic secondary products;
• and
• d. boric acid from the aqueous component is recycled to (a);
• the improvement which comprises
• e. crystallizing boric acid from the aqueous phase to deposit therefrom the boric acid which is recycled to (a), thereby leaving a saturated aqueous mother liquor containing boric acid;
• f. oxidizing at least part of the residual saturated boric acid-containing mother liquor from (e) in the liquid phase with a gas comprising molecular oxygen at a temperature of at least 200.degree. C and under a pressure sufficient to keep at least some of the water in the liquid phase so that the organic impurities contained in said mother liquor are oxidized to an extent of from about 41 to 94%;
• and
• g. recycling the resulting aqueous solution containing boric acid from step (f) to the hydrolysis of step (b).