In a process for producing sec-butylbenzene, a C4 olefinic hydrocarbon feedstock comprising isobutene and at least one n-butene is contacted with methanol and/or water in the presence of an acid catalyst to selectively oxygenate isobutene to produce an effluent stream rich in n-butene and containing less isobutene than the feedstock. The effluent stream is then contacted with benzene under alkylation conditions and in the presence of an alkylation catalyst to produce alkylation stream comprising sec-butylbenzene.