(585az) Insights into the Isobutane Alkylation with Butene Catalyzed By the Combination of so3h-Functionalized Ionic Liquids and Sulfuric Acid

The alkylation of isobutane producing alkylates is a significant process in chemical industry due to the advantages of alkylates, such as high octane value, low vapor pressure, less olefin and aromatic hydrocarbon. In this work, the isobutane alkylation with butene catalyzed by sulfuric acid together with SO₃H-functionalized ionic liquids (ILs) [C_nPSIm][HSO₄] as co-catalysts was researched. The results show that the catalytic performances such as alkylate quality become better when the length of the alkyl substituent on [C_nPSIm][HSO₄] is longer, which improves the isobutane solubility in catalyst phase. When the [OPSIm][HSO₄] ([C_nPSIm][HSO₄], n=8) was added, the best catalytic activity was achieved with the research octane number (RON) of 96 and the ratio of trimethylpentane (TMP) to dimethylhexane (DMH) of 10.0. The reusability of [OPSIm][HSO₄]/H₂SO₄ can reach up to 22 runs, which is much longer than the non-SO₃H-functionalized [OMIm][HSO₄]/H₂SO₄. The quantum chemistry calculations revealed that cationic clusters [[OPSIm](H₂SO₄)_n]⁺ (n=0, 1, 2, 3) were formed by the strong hydrogen bond between the sulfonic acid group and H₂SO₄. The clusters make the SO₃H-functionalized ILs act as a buffering agent and improve the reusability of H₂SO₄. The quantum chemistry calculations results were further confirmed by ¹H-NMR spectra. Hopefully, the obtained results in this work would bring valuable insights into the design of new alkylation catalysts and the enhancement of cycling of the traditional H₂SO₄ catalyst.