Fouling rate inhibition for a hydrogenation reactor. A hydrocarbon hydrogenation method comprises passing a liquid feedstream through a magnetic field to separate magnetically susceptible particles, and introducing the magnetically lean stream into a fixed catalyst bed under hydrogenation conditions to saturate carbon-carbon double bonds in the hydrocarbon. Also, a hydrogenation reactor system comprises a magnetic conditioning zone, an inlet flow path to introduce a magnetically lean stream from the magnetic conditioning zone into a fixed catalyst bed and an outlet flow path from an outlet end of the catalyst bed to withdraw reactor effluent.