Procédé de déshydratation de l'acide borique

Orthoboric acid is dehydrated by maintaining a slurry thereof, in an organic liquid, at a temperature of 110-160 DEG C., until at least 50% is dehydrated to metaboric acid. Further dehydration of the boric acid may be carried out at a higher temperature. The organic liquid may be a saturated or unsaturated hydrocarbon having 4-30 C atoms or a hydrocarbon substituted by, e.g., hydroxyl, sulpho, nitrile, borate, or carboxyl groups. The orthoboric acid may be present as 0.1-20% by wt. of the slurry. The slurry may be introduced continuously into a large body of the organic liquid maintained at the required temperature, a continuous stream of metaboric acid slurry being withdrawn therefrom. Gases inert to the reactants, e.g. N2 or air, may be used as stripping gases. The distillate of organic liquid and H2O may be condensed, separated and the organic liquid recycled to the reaction.ALSO:Borate esters are produced by contacting with molecular oxygen a slurry of metaboric acid produced by heating a slurry of orthoboric acid in an organic liquid to a temp. of 110 DEG -160 DEG C. until at least 50% of the acid is dehydrated to metaboric acid. The orthoboric acid may be further dehydrated by heating at a higher temp. before the oxidation. The organic liquid may be a saturated or unsaturated hydrocarbon having 4-30 C atoms, or a hydrocarbon substituted by e.g. OH, sulpho, nitrile borate or carboxy groups. In the example a slurry of metaboric acid in cyclohexane is produced, oxidized at 120 DEG C. with O2 to the ester, and then hydrolized to produce cyclohexanol and cyclohexanone. The boric acid produced in this hydrolysis is recovered and recycled.