Dehydration of .alpha.-methylbenzyl alcohols to form monovinylidene aromatic monomers

A process for preparing a monovinylidene aromatic monomer by dehydrating .alpha.-methylbenzyl alcohol which comprises a dehydration step of contacting the alcohol in vapor phase with a dehydration catalyst consisting essentially of silica gel in the form of a divided solid having a surface area of at least about 300 m.sup.2 /g, said dehydration step being carried out at temperatures from about 200.degree. to about 510.degree. C., and a step of subjecting the product of the dehydration step to simple distillation to obtain styrene in purity greater than 99 mole percent which styrene contains less than 1 mole percent of ethylbenzene impurity.