The apparatus includes an alkylation unit connected to a first benzene recycle conduit, a feed conduit and an alkylation effluent conduit; a transalkylation unit connected to an polyalkylbenzene recycle conduit, a second benzene recycle conduit, and a transalkylation effluent conduit. A dividing wall distillation column is in fluid communication with the transalkylation effluent conduit, the alkylation effluent conduit, a product stream, a bottoms stream conduit and first and second benzene recycle conduits. A polyalkylbenzene fractionation column is connected to the bottoms stream conduit, the polyalkylbenzene recycle conduit and a heavy component conduit.