Catalytic oxidations with sulfur dioxide: II. Alkylaromatics

Abstract The catalytic oxidation of ethylbenzene with sulfur dioxide gives styrene in high yields (90% selectivity at 95% ethylbenzene conversion) over a number of catalysts. Catalyst activity declines due to coke formation but activity can be restored by air regeneration. The reaction rate increases almost linearly with pressure, with a similar increase in coke formation. Water retards the rate. Both ethyl groups in the diethylbenzenes can be converted to vinyl groups but the ortho -divinylbenzene is very rapidly cyclized to naphthalene. Alpha-methylstyrene is produced from isopropylbenzene in only 60–70% selectivity due to side reactions. Toluene is converted to a solid product containing both sulfur and oxygen. 1,5-Cyclooctadiene, 1,5,9-cyclododecatriene, and 1,2,4-trivinylcyclohexane are not converted to vinylic benzenes in high selectivity, due to competing reactions.