Gluconic acid catalytic oxidation

In 2006, Beltrame et al. investigated the catalytic activity of a colloidal solution of gold in the selective oxidation of o-glucose to o-gluconic acid. This reaction was performed at 303-333 K in water, at atmospheric pressure and with different glucose and oxygen concentrations at a pH of 9.5 [122]. The results showed that the reaction rate was proportional to the oxygen concentration. 

As for hydrogenation, heterogeneous catalytic oxidation of carbohydrates was essentially performed in the presence of carbon-supported metal catalysts, namely Pt, Pd or Bi-doped Pd.[57] Oxidation of glucose into gluconic acid, the worldwide production of which is around 60000 tons year 1,[52] is used in the food and pharmaceutical industry, and is produced today by enzymatic oxidation of D-glucose with a selectivity in gluconic acid close to 100%. 

Oxidation of lactose and maltose with Au/Ti02 catalysts has been reported to give close to 100% selectivity to lactobionic acid and malto-bionic acid, respectively63 which have potential uses in the pharmaceutical and detergent industries, as well as in food. Studies of the catalytic conversion of glucose by hydrogenation and oxidation to produce sorbitol and gluconic acid respectively have also been reported.64 Sorbitol is also manufactured on a 60 000 tonnes per annum scale. 

One important application is in the field of carbohydrate transformations, the catalytic oxidation of D-glucose to D-gluconic acid represents an economically competitive route with respect to biochemical oxidation [4], This new process is the result of extensive studies on the selective Cl-hydroxyl group oxidation in the presence of O2 using a Pt or Pd catalyst modified with cocatalysts [5]. 

The selective oxidation of D-glucose into gluconic acid was selected as catalytic test reaction. The reactor vessel and the experimental conditions were described in detail elsewhere [8]. The pH of the reaction mixture was kept at a constant value in the range 9.25-9.45 by adding a 20 wt.% aqueous solution of sodium hydroxide with an automatic titrator (Stat Titrino 718) from METROHM. The base consumption was recorded as a function of time. 

The results of the kinetic investigations proved that glucose oxidation mechanism is the same as established for other substances oxidized in the presence of this catalytic system. The kinetic equation of gluconic acid formation rate appears as follows ... 

The selective oxidation of D-glucose into gluconic acid was selected as catalytic test reaction. The reactor vessel and the experimental conditions were described in detail elsewhere... 

Other interesting targets for applications of catalytic oxidation of sugars may include the synthesis of free gluconic acid [23] and antiscaling polycarboxylated sugar [26-28]. 

Deller, K., Krause, H., Peldszus, E., and Despeyroux, B. (1989) Catalytic oxidation of glucose to gluconic acid. Patent DE 3823301. 

C9 Selective catalytic oxidation Gluconic acid Pd/Al203 catalyst Food and [38]... 

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