1. AN IMPROVED APPARATUS USEFUL FOR HYDROGENATION COMPRISING, IN COMBINATION: A REACTOR; FEED CONDUIT MEANS CONNECTED TO ONE END OF SAID REACTOR; AN EFFLUENT CONDUIT COMMUNICATING BETWEEN THE OTHER END OF SAID REACTOR AND A VAPOR-LIQUID SEPARATION MEANS; A VAPOR OUTLET AND A LIQUID OUTLET IN SAID SEPARATION MEANS; A LIQUID RECYCLE CONDUIT MEANS COMMUNICATING BETWEEN SAID LIQUID OUTLET AND SAID FEED CONDUIT; A QUENCH ZONE DISPOSED IN SAID FEED CONDUIT BETWEEN SAID RECYCLE CONDUIT MEANS JUNCTURE AND SAID REACTOR; A HEATER DISPOSED IN SAID FEED CONDUIT MEANS BETWEN SAID RECYCLE CONDUIT MEANS JUNCTURE AND SAID QUENCH ZONE; A RECYCLE QUENCH CONDUIT COMMUNICATING BETWEEN SAID LIQUID RECYCLE CONDUIT AND SAID QUENCH ZONE; A TEMPERATURE INDICATING MEANS OPERATIVELY CONNECTED TO SAID REACTOR EFFLUENT CONDUIT; FIRST CONTROL VALVE MEANS DISPOSED IN SAID RECYCLE CONDUIT; SECOND CONTROL VALVE MEANS DISPOSED IN SAID RECYCLE QUENCH CONDUIT; A FIRST FLOW CONTROLLER OPERATIVELY RESPONSIVE TO SAID TEMPERATURE INDICATING MEANS AND OPERATIVELY CONTROLLING SAID FIRST CONTROL VALVE MEANS; A SECOND FLOW CONTROLLER OPERATIVELY RESPONSIVE TO THE UPPER RANGE OF SIGNALS FROM SAID TEMPERATURE INDICATING MEANS, AND OPERATIVELY CONTROLLING SAID SECOND CONTROL VALVE MEANS; SAID FIRST FLOW CONTROLLER BEING ADAPTED TO AUTOMATICALLY ADJUST SAID FRIST VALVE BY OPENING SAME, SAID SECOND VALVE BEING CLOSED, ABOVE A FIRST PREDETERMINED OPTIMUM TEMPERATURE WHEREBY SAID FIRST VALVE IS MORE FULLY OPEN; AND SAID TEMPERATURE INDICATING MEANS BEING FURTHER ADAPTED TO AUTOMATICALLY RESET SAID SECOND FLOW CONTROLLER SO AS TO ADJUST SAID SECOND VALVE BY OPENING SAME, WHILE ABOVE A SECOND AND HIGHER PREDETERMINED TEMPERATURE, UNTIL SAID SECOND VALVE IS FULLY OPEN.