Isobutene dimerization of C4 mixtures with the simulated components of industrial fluid catalytic cracking (FCC) gas stream was carried out in a fixed-bed microreactor over the acid ion-exchange resin (DH-2) in the presence of ethanol. The influences of ethanol/isobutene molar ratio and reaction temperature on the isobutene dimerization reaction were studied. For 1-butene, both isomerization and oligomerization simultaneously take place, but the isomerization reaction is more sensitive to reaction temperature than oligomerization. And both reactions were inhibited noticeably in the presence of ethanol. Although the conversion of isobutene was reduced to some extent when ethanol was introduced, it was beneficial for improving the weight fraction of dimers in oligomers as well as trimethylpentenes in dimers. With ethanol addition, the dimerization reaction was less sensitive to the reaction temperature thus the isobutene dimerization reaction can be performed in a wide temperature range. [GRAPHICS] .