PURPOSE: To produce 1,3-butadiene, by passing a 4C fraction free from isobutene through a synthesizing step (A) of butadiene or without passing the 4C fraction through the above-mentioned step, feeding the 4C fraction to the intermediate tray of an extractive distillation column, and recycling a vapor stream above a feed tray of an effluent from the step (A) and below a feed tray of a selective solvent through the step (A).
CONSTITUTION: Only isobutene is mainly removed from a 4C fraction in a raw material preparation step, and the raw material containing intact n-butenes and butanes is fed to a synthesizing step (A) of butadiene (or directly to an extractive distillation column) and dehydrogenated or oxidatively dehydrogenated to give a hydrocarbon fraction (C fraction) containing 1,3-butadiene, whch is then fed to the extractive distillation column and distilled in an atmosphere of a selective solvent to afford a fraction consisting essentially of 4C paraffin from the top of the extractive distillation column. A fraction consisting essentially of n-butene is taken out of a tray above a feed tray of the C fraction and below a feed tray of the selective solvent as a side stream, and recycled through the step (A) to give the aimed fraction consisting essentialy of 1,3-butadiene from the bottom of the column.
YOSHIOKA MASAO
NAKAZAWA KAZUMI
