Chlorination of butadiene

In a process of chlorinating butadiene to produce principally dichlorobutenes by feeding a reactor with a mixture of butadiene vapor and chlorine vapor, the butadiene to chlorine ratio being in excess of one mole of butadiene to one mole of chlorine, recovering the dichlorobutenes from the reactor and recycling unreacted butadiene back to the reactor;

• the improvement which consists essentially of feeding the reactor with a mixture of butadiene vapor and chlorine vapor in a mole ratio of from 5:1 to 50:1 butadiene to chlorine, the entering vapor mixture being maintained at a temperature of from 70.degree. to 175.degree. C., maintaining the temperature of the vapor mixture in the reactor at from 70.degree. to 250.degree. C. whereby substantially all of the chlorine is reacted, conducting the product from the reactor to the lowest tray in a multiple tray scrubber-cooler and feeding makeup liquid butadiene to one or more upper trays of the scrubber-cooler, condensing the dichlorobutenes and separating them from unreacted butadiene while vaporizing the makeup liquid butadiene, the head temperature of the scrubber-cooler being maintained at from 45.degree. to 80.degree. C. by the makeup liquid butadiene and by recycling part of the scrubber-cooler bottom stream through a cooler and back to one or more upper trays of the scrubber-cooler, recycling the unreacted butadiene and the vaporized makeup butadiene from the scrubber-cooler to the reactor and recovering condensed dichlorobutenes.