Gas-phase oxychlorination of benzene

✍ Scribed by Jan G. P. Born; Hans W. A. van der Wart; Peter Mulder; Robert Louw

• Book ID: 104589511
• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 986 KB
• Volume: 112
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19931120405

✦ Synopsis

Abstract

Homogeneous gas‐phase oxychlorination of benzene has been examined in a flow system between 722 and 1174K. Experiments were performed at atmospheric pressure with nitrogen as an inert carrier gas, containing about equal molar amounts of oxygen, HCl and benzene. Apart from chlorobenzene, substantial amounts of o‐ and p‐chlorophenol are produced. Using benzonitrile rather than benzene, the three isomers of ClC~6~H~4~CN are formed in about equal amounts. These findings suggest a homolytic mechanism with aryl radicals as key intermediates. Thermokinetic analysis points to formation of chlorophenols via reaction of phenoxyl (formed from phenyl and oxygen) with HOCl. Chlorination, C~6~ H~6~ → C~6~H~5~Cl, is explained by reaction between phenyl radicals and HOCl. With increasing temperature (and, therefore, oxygen consumption), slow combustion is replaced by pyrolysis as the major reaction channel. As a result, above ca. 1000K, the production of chlorobenzene diminishes, [C~6~H~5~Cl] ultimately being governed by the equilibrium: C~6~H~6~ + HCl ⇌ C~6~H~5~Cl + H~2~.