A process for the production of alkylbenzene includes introducing benzene and an olefin feed into a first alkylation reaction zone in the presence of a first alkylation catalyst under first alkylation reaction conditions to produce a first alkylation effluent containing alkylbenzene and a first alkylation overhead stream. The first alkylation overhead stream is separated into a liquid portion containing benzene and a vapor portion containing unconverted olefin and ethane. A major portion of the unconverted olefin in the vapor portion of the first alkylation overhead stream is absorbed into a de-ethanized aromatic lean oil stream containing benzene and alkylbenzene in an absorption zone to produce a rich oil stream containing olefins and at least some of the ethane. The rich oil stream is sent to a second alkylation reaction zone containing a second alkylation catalyst under second alkylation reaction conditions to produce a first aromatic lean oil stream, which is fractionated in a de-ethanizer to produces a de-ethanizer vapor overhead containing a major portion of the ethane and a liquid bottoms containing the de-ethanized aromatic lean oil.