GB589015A - Improvements in the manufacture of styrene and derivatives of styrene - Google Patents

Abstract

Styrene or its substitution derivatives are prepared by heating phenyl methyl carbinol or a substitution derivative thereof in vapour phase under a pressure below 300 mm. in contact with a dehydration catalyst. Substitution derivatives include alkyl, aryl or halogen, nuclear or side chain derivatives, for example 4-chlorstyrene, 4-chlor-b -chlorstyrene, 4 - brom - b - methylstyrene, 4 - ethylstyrene, 2-, 3- and 4-methylstyrenes, and a -methylstyrene. For phenyl methyl carbinol, pressure is preferably below 100, especially 30-70 mm., and temperature above 300 DEG , especially 350-450 DEG C. Preferred conditions are about 50 mm. and 380-420 DEG C. Activated alumina, especially in massive form, for example as pellets, is the preferred catalyst. Others include other metal oxides, and phosphoric acid or a phosphate on a carrier. Catalytic activity is restored as required by heating to 400-450 DEG C. in air. Hydroquinone or other polymerization inhibitor, for example in an amount of 0.1 per cent by weight, may be mixed with the phenyl methyl carbinol. In one example, phenyl methyl carbinol, which may contain hydroquinone, is treated at 400 DEG C. and 50 mm. with activated alumina, the products condensed and stratified, and the upper layer distilled at 50 mm. in presence of hydroquinone. The 4-chlor derivative is similarly dehydrated at about 45 mm.