Interphase Distribution of Triflic Acid and Acid-Soluble Oil in the Isobutane Alkylation with Olefins

The interphase distribution of trifluoromethanesulfonic acid (TfOH) and acid-soluble oil (ASO) in a two-phase liquid mixture of these components and hexane was studied at 25°C. This system is a model for isobutane alkylation reactions with olefins in the presence of liquid acid catalyst partially soluble in hydrocarbons. UV spectrophotometry and acid–base titration were used to measure the total equilibrium concentrations of free and combined TfOH and ASO depending on the molar ratio of ASO to TfOH. The obtained data on the interphase distribution of TfOH and the ASO were explained assuming three equilibria: (1) TfOH interphase distribution (solubility); (2) ASO · 2TfOH complex formation; and (3) ASO · 2TfOH interphase distribution (solubility). An adequate mathematical model was developed on this basis. The equilibrium constant values were determined and the TfOH interphase distribution constant dependence on the phase composition was expressed in analytical form. The mathematical description developed is intended for the calculations of the amounts and compositions of phases and is necessary for the kinetic model design of isobutane alkylation with butenes.