Effects of aromatics on ionic liquids for C4 alkylation reaction: Insights from scale-up experiment and molecular dynamics simulation

Abstract

Alkylation of isobutane and butenes in ionic liquids (ILs) is an important industrially applied and environmentally friendly process for the production of high quality gasoline. In a scale-up reactor, we found that the ILs with a small amount of aromatics would exhibit excellent performances for the alkylation reaction. The behaviors of aromatics on the liquid-liquid interface and the alkylation performance of IL/benzene have been investigated by molecular dynamics simulations and experimental studies. Based on density profile, segment orientation, and self-diffusion coefficient, the main reason that benzene affects the IL alkylation performance was discussed. Although the amount of benzene was small, benzene would accumulate in the acid-hydrocarbon interfacial layer during the alkylation process. A little benzene was enough to buffer the strong acidity of chloroaluminate anions at the interface. The presence of benzene also provided a transport channel for reactants, increasing the concentration of isobutane at the interface. At the interface, the proper acidity and higher isobutane-to-olefin ratio significantly improved the IL alkylation performance. Effects of other aromatics on the C4 alkylation have also been studied, which further confirmed our findings in the IL/benzene alkylation reaction. Hopefully, these studies can provide useful information to the design of the ionic liquid catalysts and the optimization of the C4 alkylation process.