Alternative Hexanedioic Acid Routes

Recycling of N2O
Dinitrogen monoxide (N2O), produced when nitric acid is used to produce hexanedioic acid from KA, is difficult to remove from the waste gas stream. One solution to this is to produce the KA from benzene by a different reaction, using N2O as an oxidising agent to make phenol, rather than cyclohexane, from which the KA mixture can be produced

Alternative Feedstock
Carbohydrates, including glucose, are present in plants in huge quantities. Plants are the ultimate renewable feedstock - you simply grow more. Dr. Karen M. Draths and Professor John W. Frost of Michigan State University received the Presidential Green Chemistry Challenge award in 1998 for their work developing the synthesis of hexanedioic acid from plant-derived glucose.

This Draths-Frost method uses genetically modified bacteria, and operates in aqueous solution at relatively low temperatures. The modified bacteria produce muconic acid (an unsaturated organic acid), and this is hydrogenated to hexanedioic acid.

Hydrogen Peroxide Oxidation of Cyclohexane
Hexanedioic acid can also be made by the oxidation of cyclohexane using 35% hydrogen peroxide. Although this can be carried out easily in a laboratory, the key to a possible industrial route is the catalyst developed by Japanese researchers at Nagoya University, which allows the reaction to be carried out at 75-90°C. Unlike other attempts at using hydrogen peroxide, this method does not use organic solvents, and does not use halides as catalysts.

If cheaper methods for hydrogen peroxide production can be developed, this approach may become commercially viable.

.diagram: alternative routes to "KA"


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