Daicel Chemical Industries Ltd. (Osaka, Japan; edlinks.chemengonline.com/6900-540) is further developing an oxidation catalyst based on N-hydroxyphthalimide (NHPI), which was first discovered by Professor Yasutaka Ishii of Kansai University several years ago (CE, September 2000, p. 23). The catalyst, together with a small amount of metal salts (Mn or Co), can be used for the one-step conversion of cyclohexane into adipic acid with high (80%) yield and without producing nitrous oxide as a byproduct. Conventional adipic acid production requires two steps, suffers from low (3–7%) yields and generates large quantities of N2O, a strong greenhouse gas, says the company. The company has developed an inexpensive method for making NHPI from a diabasic carboxylic acid — a byproduct from adipic acid production — and succeeded in reducing the volume of NHPI catalyst required to make adipic acid by two orders of magnitude over previous studies.
An adipic acid plant with a capacity of at least 30-m.t./yr has been built at Daicel Chemical’s site at Himeji, Japan. The plant will be operated as part of a government-supported project, led by Prof. Ishii, with cooperation from three other companies. The project aims to promote the development of NHPI catalyst for alkane oxidation under milder conditions. The one step, N2O-free process is expected to become the greener route for making adipic acid in the future, says the firm.