Adipic Acid
Adipic acid (ADA) is a six-carbon molecule with a chemically reactive carboxylic acid group at each end used to produce nylon 66. It is produced from the oxidation of a mixture of cyclohexanol and cyclohexanone (ketone-alcohol or KA oil) with nitric acid; this KA oil in most cases is derived from cyclohexane and cyclohexene, while less than 5% is from a phenol route. Unlike other nylon intermediates, ADA is also extensively used elsewhere. It is a widely used dicarboxylic acid in many non-nylon applications, such as paints, coatings, solvents, plasticizers, polyurethanes, pharmaceuticals, flue gas desulfurization, glass protection, briquetting and leather tanning agents, food additives, cosmetics, detergent tablets, and as a copolymer in unsaturated polyester resins. Competitive dicarboxylic acids include succinic, glutaric, and sebacic acid and are used primarily in non-nylon applications, often as biogenerated alternatives to castor oil–derived ADA.