Oxidation to Free Gluconic Acid

No direct method is yet known for the preparation of free gluconic acid, which is presently manufactured from calcium gluconate and sulfuric acid with a large amount of CaS04 as a by-product This is due to the fact that at low pH values the enzymatic catalysis is inhibited, and also Pd, Pt, and Au catalysts are scarcely 

Following the initial screening of Au and Pd, Pt, Rh, the most promising Au + Pt combination was optimized, leading to a quite active catalyst for alkali-free oxidation of glucose containing gold and platinum in the ratio 2 1 (w/w). 

The synergetic effect of the two metals is quite evident considering Fig. 13.12 [48]. 

The feasibility of the one-step synthesis of gluconic acid with promising TOF values around 1000 h is demonstrated, but critical experiments concerning the catalyst life are presently lacking. 

Perspective for Cold Catalysis in Liquid Phase Oxidation 

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