High-purity butene-1 isolated from steam cracker butene(s) - by conversion of isobutene to methyl tert. butyl ether and fractionation

The prepn. of butene-1 of purity above 99% from an olefinic C4 cut comprises: (i) conversion of isobutene to methyl tert. butyl ether (MTBE) by reaction with methanol over an acid catalyst; (ii) fractionation of the prod. from (i), giving MTBE, MeOH for recycle to (i), and remaining C4 hydrocarbons; (iii) selective hydrogenation of the latter to remove butadiene traces; (iv) treatment of the prod. of (iii) in a debutaniser; (v) treatment of the deisobutanized (bottom) prod. from (iv) in a superfractionator, giving butene-1 overhead. Used in treating the C4 cut from steam cracking after removal of most of the butadiene. The butene-1 can be used as a comonomer in h.d. polyethylene. The catalyst in (i) is a liq. acid, e.g. H2S04, or pref. a solid contg. -S03H groups, Pref. sulphonated polystyrene-divinylbenzene. The molar ratio MeOH/isobutene is pref. 1-10, the temp 40-100 deg.C and the space velocity 0.5-20/h. L'INVENTION CONCERNE UN MOYEN D'OBTENTION DU BUTENE-1 DE PURETE SUPERIEURE A 99, A PARTIR D'UN EFFLUENT DE PRODUCTION DE METHYL TERTIO-BUTYL ETHER, LUI-MEME OBTENU PAR ACTION DU METHANOL SUR L'ISOBUTENE D'UNE COUPE C OLEFINIQUE.L'INVENTION EST CARACTERISEE EN CE QUE LEDIT EFFLUENT, APRES EN AVOIR SOUTIRE LE METHYL TERTIO-BUTYL ETHER, EST SELECTIVEMENT HYDROGENE, PUIS ENVOYE DANS UNE ZONE DE DEISOBUTANISATION, PUIS FRACTIONNE.L'INVENTION S'APPLIQUE EN PARTICULIER AU TRAITEMENT D'UNE COUPE C OLEFINIQUE EN PROVENANCE D'UN CRAQUAGE A LA VAPEUR D'EAU.