Process for producing premium gasoline by polymerizing C.sub.4 cuts

摘要

The invention relates to a process for producing premium gasoline from olefinic C.sub.4 cuts containing 1- and 2-butenes and isobutene, the process consisting of converting at least 97% of the total isobutene content of the charge and at least the major portion of the 1- and 2- butenes thereof to C.sub.4 hyrocarbons dimers and trimers without producing substantial amounts of kerosene, said process being characterized in that, in a first step, the olefinic C.sub.4 cut is treated in a first polymerization catalytic zone so as to convert at least 80% of the isobutene to isobutene dimers and trimers and to convert at most 45% of the mixture of 1- and 2-butenes to dimers and trimers thereof, in that, subsequently, the effluent from said first catalytic polymerization zone is fractionated so as to recover, on the one hand, from the column bottom, essentially the C.sub.4 olefinic hydrocarbon dimers and trimers and, on the other hand, from the top of the column, a mixture containing the major part of the isobutene and 1- and 2-butenes not converted in said first catalytic polymerization zone, said mixture being, during a second step, at least partly fed to a second catalytic polymerization zone so as to convert (a) substantially the total amount of isobutene to isobutene dimers and trimers in said second zone and (b) at least 50% of the 1- and 2-butenes, supplied to said second zone to n- butenes dimers and trimers.