Modeling of side reactions of isobutane alkylation with butenes catalyzed by trifluoromethane sulfonic acid

The 2,2,4-trimethylpentane (2,2,4-TMP) decomposition kinetics in the presence of trifluoromethane sulfonic acid (TfOH) and acid soluble oil (ASO) was studied at the temperatures of 15-35 °C in a wide concentration range. 2,2,4-TMP partially undergoes isomerization during the reaction. The adequate kinetic model is designed for isooctane sum decomposition including light ends, heavy ends, and ASO formations. In this model heavy ends are the intermediate in ASO formation. Light ends' evolving accompanies both heavy ends and ASO formations. Rate equations are first order in catalyst concentration and its Hammett proton activity controlled by ASO content. In particular the heavy ends formation rate is first order in isooctanes concentration, slowed down by light ends and auto-accelerated by heavy ends. The ASO formation rate is 0.6 orders in heavy ends' concentration, slowed down by light ends, and accelerated by isooctanes and heavy ends. The reaction mechanism explaining all these phenomena is proposed and discussed in connection with practice of commercial isobutane alkylation with olefins.