Dehydration of phenyl-ethanol to styrene: Zeolite catalysis under reactive distillation

Styrene is commercially produced by the dehydration of phenyl-ethanol with co-production of propene oxide. We investigated the possibility of carrying out this reaction at mild temperatures under reactive distillation conditions. Medium-pore zeolites, such as H-ZSM-5 and H-ZSM-11, were found to be very active and selective at 170 °C. The Lewis-acidic TS-1 zeolite showed similarly high selectivity but lower activity. High activity and selectivity required small (<50 nm) zeolite crystals. In contrast, large-pore zeolites and mesoporous solid acids did not produce much styrene under these conditions. These results show the importance of shape selectivity. The styrene selectivity rapidly degraded with time on stream, however, leading to the formation of ethers and, subsequently, styrene oligomers. No simple model can explain all of the factors affecting ether formation.