METHOD OF 2, 3 TO 4, 6-DIISOPROPYLIDENE-2-KETO-L-GULONIC ACID PREPARATION

The invention concerns a method of preparation of 2,3 : 4, 6-diisopropylidene-2-keto-L-gulonic acid which is an intermediate product in the production of ascorbic acid - vitamin C. 2,3 : 4,6-diisopropylidene-2-keto-L-gulonic acid is prepared by oxidation of 2,3 : 4,6-diisopropylidene-L-sorbose with dioxygen at 80 to 135 degrees C and oxygen partial pressure of 2 to 100 kPa in the presence of a catalyst. The principle of the invention is that the reaction occurs in a water-alkaline environment with a pH higher than 7.5 in the presence of a heterogeneous catalyst on a base of palladium coated on active charcoal with a content of palladium of 1 to 20 % by weight, based on the weight of the carrier in a quantity of 0.2 to 1 % by weight of palladium related to the weight of 2,3 : 4,6-diisopropylidene-L-sorbose, activated by compounds of cobalt or manganese in dissoluble form in the water-alkaline environment in a molar ration to palladium of 0.2 to 1.1.