FIELD: petrochemical processes. SUBSTANCE: oligomerization of isobutylene is carried out in presence of catalyst, tert-butanol as selectivity-increasing modifier, and isoalkane diluter containing largely isooctane in amount sufficient to increase selectivity with regard to dimer and exothermic reaction heat absorption. In this case, at least a part of isooctane is prepared by isobutylene dimer hydrogenation. EFFECT: increased isobutylene dimer-regarding selectivity. 4 cl, 1 dwg
