A hydrotreating reactor including a vessel comprising an upper zone, and intermediate zone and a lower zone. The upper zone comprises at least one upper catalyst bed. The intermediate zone comprises a vapor/liquid separation zone, wherein gas separated within the vapor/liquid separation zone is directed to a high pressure knockout drum and the liquid separated within the vapor/liquid separation zone is directed to a stripping section and then the lower zone. The lower zone comprises at least one lower catalyst bed. Preferably, the stripping section is configured and arranged for removing hydrogen sulfide and ammonia from the gas.