TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst comprises nickel, palladium, platinum, and/or cobalt dispersed over refractory inorganic oxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The hydrogenation feedstream comprises benzene ( greater than or equal to 90 wt.%) and unsaturated aliphatic hydrocarbons ( greater than or equal to 100 ppm). The unsaturated aliphatic hydrocarbon is 4-6C diolefin, preferably 1,3-butadiene, 1,2-butadiene, 1,4-pentadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,2-butadiene, 1,4-hexadiene, 2,3-dimethyl-1,3 -butadiene, and/or 1,3-hexadiene. The nitrogen compound is acetonitrile. The hydrogenation feedstream has nitrogen content of 1-10 ppm and bromine number of greater than or equal to 0.030. The hydrogenation feedstream is ethylbenzene dehydrogenation reactor effluent stream or overhead from benzene/toluene distillation column. Preferred Method: Reaction of hydrogenation feedstream with hydrogenation catalyst is conducted at 50-300 degrees C and 1-52 barg to provide hydrogenation effluent stream having bromine number of less than or equal to 30% of the bromine number of hydrogenation feedstream. At least 80% of diolefins in the hydrogenation feedstream are hydrogenated and at least 90% of benzene in the hydrogenation feed stream is unconverted. The method further includes combining hydrogenation feedstream with makeup hydrogen stream at molar hydrogen:degree of unsaturation ratio of 0.5:1-10:1, prior to or during reaction with hydrogenation catalyst; and reacting the hydrogenation effluent with zeolitic guard bed to remove a portion of nitrogen compounds. EXAMPLE - A hydrogenation feedstream containing benzene, diolefins as pentadiene or hexadiene (1000 ppm), monoolefins as pentene (300 ppm), and acetonitrile (100 ppm) was selectively hydrogenated by passing over palladium-containing catalyst at 120 degrees C, 28 barg and liquid hourly space velocity of 25/hour. Hydrogen was added at molar ratio of 5, based on the total moles of diolefins and acetonitrile in the hydrogenation feedstream. Conversion of diolefins was 92.9%, while saturation of benzene was negligible.