The selective saturation of unsaturated aliphatic hydrocarbons (e.g., diolefins) in a hydrogenation feed stream comprising an aromatic compound (e.g., benzene) and one or more nitrogen compounds renders it beneficial when the stream or a portion thereof is subsequently treated (e.g., with a zeolitic adsorbent) to remove nitrogen. In particular, the selective saturation of, for example, olefins and diolefins prolongs the life of the nitrogen guard bed. In a representative embodiment, the selective hydrogenation is applied to a recycle benzene-containing stream recovered in the separation section (e.g., from the benzene/toluene splitter overhead) of a styrene production process, prior to treatment with a nitrogen guard bed adsorbent.