High-purity butene-1 and high-octane gasoline are obtd. as follows from an olefinic C4 cut, low in butadiene, e.g. from a steam cracker. (a) The feedstock is polymerised-dismutated, giving largely a mixt. of jet-fuel cut, gasoline, butenes-2, and esp. butene-1. (b) The prod. is fractionated to a mixt. (i) of gasoline and jet-fuel cut, and a mixt. (ii) of butanes and butenes. (c) The C4 mixt. (ii) passes to finishing-polymerisation, where more than 90% of the isobutene is converted to gasoline. (d) The step (c) prod. is fractionated into a gasoline (iii) comprising mainly butenes dimers and trimers, and another C4 mixt. (iv). (e) The latter (iv) is selectively hydrogenated to reduce the butadiene concn. to 10 ppm of the butene-1. (f) The prod. is debutanised, removing most of its isobutane. (g) The debutanised fraction is fractionated into butene-1 (v) of minimum purity 99 wt.%, and a mixt. (vi) of largely butenes-2 and n-butane. (h) The gasoline (iii) and the mixt. (i) of gasoline and jet-fuel cut are mixed, for possible further treatment. Upgrading of the olefinic C4 cut is improved.
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