In the second process, reaction mixtures rich in cyclohexanone are preferred. The air oxidation is conducted in the liquid phase, usually in acetic acid as solvent, at 80-85°C and 6 bar in the presence of Cu- and Mn-acetate. Adipic acid crystallizes from the product solution as it cools. The crude product is purified by recrystallization. The selectivity to adipic acid is said to approach that of the HNO, process. The advantage of the air oxidation lies mainly with the absence of corrosive HNOl. Scientific Design has developed an up-to-datc procedure for the process involving both stages, starting from cyclohexane and going through the KA mixture to adipic acid. A 10000 tonne-per-year plant was operated by Rohm & Haas in the USA for several years, but was abandoned due to poor product quality. Other processes using boric acid wcre introduced by Stamicarbon and IFF