PROCESS FOR PRODUCING 1,3-BUTADIENE OR 2-METHYL-1,3-BUTADIENE OF HIGH PURITY

摘要

In a process for producing butadiene or isoprene having a high purity comprising a step of treating a C4 or C5 hydrocarbon mixture containing butadiene or isoprene by an extractive distillation method in the presence of a selective solvent to obtain crude butadiene or crude isoprene and a step of separating a heavy fraction contained in a small quantity in the thus obtained crude butadiene or crude isoprene by a conventional distillation method in a heavy fraction separating tower, the heat energy can be saved to a great extent by thermally coupling the tower for distilling crude butadiene or crude isoprene used in the above-mentioned extractive-distillation step with the above-mentioned heavy fraction separating tower, namely by feeding a part or the whole of the vapor stream from the top of said tower for distilling crude butadiene or isoprene to said heavy fraction separating tower and feeding a liquid at a rate corresponding to the whole or a part of the reflux rate necessary for the operation of the tower for distilling crude butadiene or crude isoprene, from the heavy fraction separating tower to the tower for distilling crude butadiene or crude isoprene.