Process for producing 1,3-butadiene

A process for producing 1,3-butadiene, which comprises feeding a fraction comprising as the main components C.sub.4 -paraffins and C.sub.4 -olefins but substantially free from isobutene (fraction D) to an extractive distillation column (column B);

• distilling the fraction in the presence of a selective solvent in column B while withdrawing a fraction comprising C.sub.4 -paraffins as the main hydrocarbon component from the top of column B, and while withdrawing as a side stream a fraction comprising n-butenes as the main component from a stage on the lower side of the selective solvent-feeding stage and on the upper side of the stage to which the C.sub.4 -hydrocarbon fraction containing 1,3-butadiene obtained from the dehydrogenation or oxdative dehydrogenation step (step A) is fed and feeding the side stream to step A to convert the n-butenes to 1,3-butadiene;
• feeding the thus obtained 1,3-butadiene-containing C.sub.4 -hydrocarbon fraction, alone or in combination with fraction D, to column B;
• and distilling the fraction in column B while withdrawing a fraction comprising 1,3-butadiene as the main hydrocarbon component and also containing the selective solvent from the bottom of column B and separating 1,3-butadiene from said fraction.