detailed description of various disperser packings is described in u s pat no 6 774 275 which is incorporated herein the open space in dumped beds or in structures having fine particles is low i e less than 50 volume open space in other embodiments the disperser packing material preferably comprises at least 50 volume open space up to about 99 volume open space the present process preferably employs a downflow reactor packed with contacting internals or packing material and catalyst through which passes a concurrent multi phase mixture of hydrocarbon containing the mixed c4s hydrogen catalyst and reactants at the boiling point of the system the system comprises a liquid hydrocarbon phase and a hydrocarbon hydrogen phase the pressure is preferentially higher at the top of the reactor than at the bottom in the present invention butadiene was converted to butylene in a 1 u2033 downflow boiling point reactor operating in the pulse flow regime excellent selectivity and activity were achieved for the present process the exact conditions for pulse flow are unknown the transition line of the pulse flow regime in a 1 u2033 packed column was calculated and plotted for the c 4 h 2 system by both the baker parameters and froude.