Reaction Behaviors and Mechanism of Isobutane/Propene Alkylation Catalyzed by Composite Ionic Liquid

Alkylation performance of isobutane with propene catalyzed by composite ionic liquid (CIL) was deeply investigated. Critical components of alkylate were C7 isoparaffins, which were mainly 2,3-dimethylpentane and 2,4-dimethylpentane. The optimal reaction conditions were as follows: reaction temperature of 15 °C, reaction time of 5 s, stirring rate of 1500 rpm, IL/HC ratio of 1.0, and I/O ratio of 68. Under these conditions, the yield of C7 isoparaffins was 78.9 wt %, and the research octane number of alkylate was 86.2. The reaction mechanism and pathway of isobutane/propene alkylation were proposed on the basis of component distribution. C7 isoparaffins were mainly from direct alkylation, and C8 isoparaffins were mainly from disproportionation. Compared with traditional concentrated sulfuric acid and hydrofluoric acid catalysts, more direct alkylation and less self-alkylation occurred, and the yield of propane was much lower when CIL was used. It was also proved that propene could be used in the CIL-catalyzed alkylation industrial unit due to the low propane production.