NOVELTY - Treatment of hydrogenation feedstream comprising aromatic compound(s), nitrogen compound(s) and unsaturated aliphatic hydrocarbon(s) includes reacting hydrogenation feedstream with a hydrogenation catalyst to selectively hydrogenate the unsaturated aliphatic hydrocarbons.    USE - Method for treating hydrogenation feedstream comprising aromatic compound(s), nitrogen compound(s) and unsaturated aliphatic hydrocarbon(s) (claimed).    ADVANTAGE - The method minimizes the loss of benzene or other desired aromatic compounds to be recycled and reacted.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for production of styrene by:    (1) reacting benzene with ethylene in benzene alkylation reactor to produce ethylbenzene effluent stream; dehydrogenating the ethylbenzene stream to produce crude styrene product stream; recovering liquid stream comprising benzene, nitrogen compounds and diolefins from the crude styrene product stream; reacting the liquid stream with hydrogenation catalyst to provide hydrogenation effluent having reduced amount of diolefins relative to the liquid stream; reacting the hydrogenation effluent with a guard bed to remove a portion of nitrogen compounds and provide a benzene recycle stream having reduced amount of diolefins and nitrogen compounds relative to the liquid stream; and recycling the benzene recycle stream to the benzene alkylation reactor; or    (2) reacting benzene with ethylene in benzene alkylation reactor to produce ethylbenzene effluent stream; dehydrogenating the ethylbenzene stream to produce crude styrene product stream comprising benzene, nitrogen compounds and diolefins; reacting the crude styrene product stream with hydrogenation catalyst to provide hydrogenation effluent having reduced amount of diolefins relative to the crude styrene product stream; recovering liquid stream comprising benzene and nitrogen compounds from the hydrogenation effluent; reacting the liquid stream with a guard bed to remove a portion of nitrogen compounds and provide a benzene recycle stream having reduced amount of diolefins and nitrogen compounds relative to styrene product stream; and recycling the benzene recycle stream to the benzene alkylation reactor.