Process for the oxidation of di-, tri-, oligo- and polysaccharides into polyhydroxycarboxylic acids

摘要

A process is provided for preparing polyhydroxycarboxylic acids by the selective oxidation of di-, tri-, oligo- and polysaccharides in an alkaline medium using an oxygenous gas in the presence of palladium on a carrier as catalyst and bismuth as promoter at a palladium concentration in the reaction mixture of at least about 40 mg/l and a molar ratio of bismuth to palladium in the range of from about 1:5 to about 1:40, in which process towards the end of the reaction, as soon as a strong increase is observed in the oxygen concentration in the liquid phase, the oxygen supply is reduced until it is not more than about 20 ppm. In this manner, virtually all of the polysaccharide added beforehand is converted into the desired end product without an unacceptably high concentration of bismuth in the end product.