A process for the production of diisobutene is disclosed wherein tertiary butyl alcohol is dehydrated to isobutene in a distillation column reactor containing an acid cation exchange resin catalyst in the form of catalytic distillation structure. The isobutene reacts with itself in the presence of the catalyst to form primarily diisobutene which is removed as bottoms from the distillation column reactor with the bulk of the water. Unreacted isobutene along with an azeotrope of water is removed as overheads with the water being separated and removed from the unreacted isobutene. A portion or all of the unreacted isobutene may be returned to the distillation column reactor as reflux.