Mathematical Description of Isobutane Alkylation with Butenes in the Presence of Trifluoromethanesulfonic Acid

Isobutane alkylation with 2-butene kinetics was studied in the presence of trifluoromethanesulfonic acid (TfOH) catalyst. The rate of this reaction is very fast and strongly dependent on acidity. Therefore, the study was conducted in the presence of compounds able to decrease the acidity (acidity controllers) and thereby to decrease the reaction rate to measurable values. The butene surplus and the reaction byproduct, acid-soluble oil (ASO), were used as acidity controllers. The rate of isooctane sum accumulation was studied in the wide variation range of reactant concentrations (from acid surplus to butenes up to a butene surplus) at temperatures from -20 to -45 °C. On the basis of the physicochemical and kinetic studies, the mechanism was suggested for the reaction predominantly proceeding in the acidic phase. The kinetic equations obtained adequately describe the main reaction routes including isooctanes and ASO formation. All route rate equations are first order on the activity of proton in the acidic phase. The effective route activation energies were determined.