As a kind of catalyst, tungstic acid has been proved to be used in the catalytic oxidation reaction of cyclohexene synthesizing adipic acid, the related researches are as bellow:
1. Fujitani ect. reported that to take 60% hydrogen peroxide as a source of oxygen, and tungstic acid catalyst catalyzed the oxidation of cyclohexene. The yield of adipic acid was 61%, with the byproducts of glutaric acid (5%), Peroxy acid (5%) and 1,2-cyclohexanediol (3%). When 35% hydrogen peroxide was used as the source of oxygen, the adipic acid was hardly obtained.
2. Oguchi etc. have taken 35% hydrogen peroxide as a source of oxygen, with tungstic acid catalyst (in tert-butyl alcohol solvent) can also directly catalytic oxidize cyclohexene synthesis of adipic acid.
The researches upon indicates that the collective effect of tungstic acid and hydrogen peroxide can play a catalytic effect; In addition, it is known that the effect of tungstic acid catalyst is not very satisfactory on the oxidation of cyclohexene to adipic acid. Experiments have shown that the tungstic acid - organic acid additive catalyst system along with 30% hydrogen peroxide to catalyze the synthesis of adipic acid by cyclohexene, with the simple process, easy to operate, and the separation yield of adipic acid can up to 90% or more.
Noted: The organic acid additives may be salicylic acid, sulfonic acid salicylic acid ect..