Production process of adipic acid

Adipic acid, also known as succinic acid, is an important organic chemical widely used in the production of synthetic materials such as polyester and nylon fibers. The production process of adipic acid mainly includes two methods: oxidation precipitation method and cyclohexanone oxidation method.
The oxidation precipitation method is currently the main production process for adipic acid. This process mainly consists of two steps: gas-phase oxidation and liquid-phase oxidation.
Gas phase oxidation is the process of vaporizing cyclohexane by heating it with steam, and then mixing it with oxygen in the air into an oxidation furnace. The oxidation reaction is carried out under the action of a catalyst (usually a mixed catalyst of vanadium, niobium, tungsten, etc.). The gas generated by the reaction is cooled by a cooling device and the organic acid is absorbed by a washing tower and an absorption tower. The adipic acid in the absorption solution is further acidified and concentrated to obtain a solution. Subsequently, the adipic acid in the solution was distilled and crystallized to obtain pure adipic acid.
Liquid phase oxidation is the process of reacting cyclohexanone with hydrogen peroxide to produce hydroquinone, which is then reacted with excess sodium hydroxide solution to obtain the sodium salt. Sodium hydroquinone reacts with hydroquinone in an acidic environment to produce adipic acid. After the reaction is complete, pure adipic acid is obtained through filtration, evaporation, and crystallization.
The cyclohexanone oxidation method is a new type of adipic acid production process. This process involves the oxidation reaction of cyclohexanone with oxygen under the action of a catalyst to obtain adipic acid and water. Catalysts are usually palladium or other precious metal catalysts. This process has the advantages of fast reaction speed, high selectivity, and environmental friendliness, but its yield is currently low and it is still in the research and development stage.
The above are the two main production processes of adipic acid. The oxidation precipitation method is currently the mainstream and widely commercialized production process, while the cyclohexanone oxidation method is an emerging green chemical production technology. With the advancement of technology and the improvement of processes, the production process of adipic acid will continue to be optimized and perfected, providing more choices and possibilities for the development of the synthetic materials industry.