An apparatus and process for treating a complex mixture of hydrocarbons containing undesirable olefinic compounds to remove the mono olefins and diolefins in two stages and separate a desirable key component from the mixture, by first treating the key component in a reactive distillation column under mild conditions to hydrogenate diolefins then separating the diolefin-depleted key component and any lighter materials from the heavier components and sending the diolefin-depleted key component and lighter materials to a second reactive distillation column where the lights are removed overhead and the diolefin-depleted key component is hydrogenated under more severe conditions to remove the mono olefins.