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.
By Marcos A. Cesar
