A process for the production of an alkylated aromatic hydrocarbon such as ethylbenzene by alkylation of benzene with an olefin such ethylene, propylene, 1-butene or isobutene with a catalyst in an alkylation reactor under liquid or gas phase conditions includes alkylating benzene with an olefin in a reaction zone at a temperature of from about 175°C. to about 500°C. and a pressure of from about 200 psi to about 800 psi, withdrawing a reactor effluent stream and separating the reactor effluent stream into a product stream and a recycle stream each containing ethylbenzene and unreacted benzene and directing the recycle stream containing ethylbenzene and unreacted benzene back to the reaction zone wherein the ratio of the liquid volume of the recycle stream to the volume of fresh benzene feed is from 0.1:1 to 50:1.