27 April 2010 14:04 [Source: Chemical Report]
There are now three synthetic routes to phenol with cumene-based technology being the dominant process. Here, benzene and propylene are reacted to form cumene, which is oxidised to the hydroperoxide, followed by acid-catalysed cleavage to yield phenol and acetone. It is considered the most economic route to phenol, supported by demand for acetone.
A small number of producers employ an older process that uses the hydrolysis of chlorobenzene. A third process is based on liquid phase oxidation of toluene in two steps, starting with the oxidation of toluene to benzoic acid, which is further oxidised to phenol.
Development work is now concentrating on technologies that avoid the coproduction of acetone. A one-step process that manufactures phenol directly from benzene without acetone by-product has been discovered by ?xml:namespace>
Mitsui Petrochemical has also developed a benzene-based process that does not coproduce acetone. Here, benzene is partially hydrogenated to cyclohexane, followed by conversion to cyclohexanol and then phenol by dehydrogenation.
Shell Chemical has developed a phenol process which coproduces both acetone and methyl ethyl ketone (MEK). According to consultants Nexant ChemSystems, it involves the co-oxidation of cumene and sec-butylbenzene, which is made via alkylation of benzene with n-butenes. The process has the potential to change the acetone/MEK ratio within reasonable limits to meet varying market demands. Although the cost of making the phenol is higher than the conventional cumene route due to higher raw material costs, the large byproduct credit received for the MEK more than makes up for these costs, says Nexant.
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