<p>A process comprising reacting a feed comprising isobutene and a modifier in the presence of an acidic solid catalyst to produce diisobutene is disclosed. The amount of the modifier in the feed is reduced as the catalyst ages. Lower reaction temperature is maintained throughout the catalyst life, which is less likely to corrode the reactor. When an alcohol is used as a modifer, a lower reaction temperature causes lower degree of dehydration of the modifier, thus lower water concentration is maintained, which in turn reduces the likelihood of reactor corrosion.</p>
