Experimental and modeling study of isobutane alkylation with C4 olefin catalyzed by Bronsted acidic ionic liquid/sulfuric acid

As a dual solvent-catalyst, sulfonic-acid-functionalized ionic liquids (SFILs) are promising catalysts for the C4 alkylation. In the present work, the effect of the SFILs with different ratios to the H2SO4 on the catalytic performance and interfacial properties for the H2SO4-catalyzed alkylation was investigated by the combination of experiments and MD simulation. Experimental results indicated that compared to pure H2SO4, the introduction of the SFILs can contribute to a higher selectivity of C8-alkylates as well as Research Octane Number (RON), suggesting a higher quality of alkylate. Moreover, the catalytic performance of the SFIL/H2SO4 catalyst is improved with the increased addition ratio of the SFIL into the H2SO4 within the range of 10 wt%. MD simulation results revealed that the obvious density enrichment of the cations of the SFILs at the interface results in a larger interface width, and higher interface number and better dispersion of C4 hydrocarbons at the interface, which can be ascribed to the location of the alkyl chains close to the C4 hydrocarbon phase with the extended and perpendicular behaviors. The improvement of interfacial properties due to the addition of the SFILs is favorable to the enhancement of the quality of alkylate, which is in excellent agreement with experimental results. Hopefully, the useful information in this work can provide a reference to the design of the SFILs and the optimization of the C4 alkylation process.