PEP Review 2002-6
Update on Phenol From Benzene via Single-Step Hydroxylation
Published: September 2003
The conventional cumene peroxidation process accounts for more than 90% of the phenol produced worldwide. However, alternative routes to phenol without coproduction of acetone continue to attract great interest. In 1996, Solutia (formerly the chemical division of Monsanto) announced a new technology to produce phenol from benzene in a single step-AlphOx. The process, jointly developed with the Boreskov Institute of Catalysis (BIC) in Russia, is based on the gas-phase reaction of benzene with nitrous oxide (N2O) over a zeolite catalyst. The major advantages of AlphOx include the use of waste nitrous oxide from adipic acid production, a high yield to phenol, and elimination of cumene (as an intermediate) and acetone (as a coproduct).
This Review updates SRIC's assessment of the AlphOx technology, based on more recent patent information. For the nitrous oxide purification step, our conceptual design uses selective catalytic reduction of NOx in the presence of ammonia and oxygen, followed by catalytic deoxidation in the presence of hydrogen. Compared with the cumene-based route, an AlphOx plant using waste N2O has a 17% lower total fixed capital investment. The net production cost for AlphOx is also very competitive and is not affected by fluctuations in the acetone market. However, for an AlphOx plant relying solely on N2O recovered from adipic acid production, phenol capacity is limited by the availability of the oxidant. A relatively small phenol plant must be integrated with a world-scale adipic acid plant for N2O supply.
Solutia and BIC are also jointly developing a technology for N2O production. The process is based on the oxidation of ammonia with air using a Mn-Bi-alumina catalyst. According to our estimates, the N2O generation step will not significantly affect the capital and operating costs for the AlphOx plant. Thus, if proven viable, the ammonia oxidation technology will solve the problem of N2O availability, making the AlphOx process economically competitive for large-scale phenol production.