Process for the selective preparation of DIB from an i-butene-containing C4 stream

Process for preparing diisobutylene (DIB) from an i-butene-containing C4 raffinate I, comprising:

• a) subjecting the C4 raffinate I to a first hydroisomerization (A) over a noble metal catalyst, with this being carried out at 30-90° C., 5-30 bar, an LHSV of 1-30 h−1 and using 3-20 standard liters of gaseous hydrogen per liter of liquid C4 raffinate I, which is above the amount of hydrogen required for the hydrogenation of highly unsaturated compounds in the C4 raffinate I;
• b) fractionally distilling the hydroisomerization product from a) in a fractionation column (B), with this being carried out at 5-25 bar and the temperature established under this pressure and 2-butene and n-butane being taken off as bottoms (4) and i-butene and i-butane being taken off at the top (8);
• c) optionally, taking a side stream (5, 7) from this fractionation column (B) and subjecting to a second hydroisomerization (C) over a noble metal catalyst, with this hydroisomerization being carried out at 30-90 ° C., at 5-30 bar, at an LHSV of 1-30 h−1 and using 3-20 standard liters of gaseous hydrogen per liter of C4 raffinate I and the hydroisomerization conditions in a) and c) being identical or different;
• d) condensing the product from the top of the column in b), dividing into two parts and subjecting the first part to a third hydroisomerization (D) over a noble metal catalyst, with this hydroisomerization being carried out at 30-90° C., at 5-30 bar, at an LHSV of 1-30 h−1, and using 0.3-20 standard liters of gaseous hydrogen per liter of condensate and the hydroisomerization conditions in a) and d) being identical or different and the hydroisomerization product from d) being recirculated to the fractionation column of b);
• e) introducing the second part of the condensed product from the top of the column in b) into a reactive column in which the C4-hydrocarbons are vaporized butanes are condensed, and returned to the reactive column, and are passed over an acidic heterogeneous catalyst, wherein iso-butene is dimerized.