Silica-immobilized ionic liquid Br?nsted acids as highly effective heterogeneous catalysts for the isomerization of n-heptane and n-octane

摘要

Metal-free imidazolium-based ionic liquid (IL) Br?nsted acids 1-methyl imidazolium hydrogen sulphate [HMIM]HSO _(4) and 1-methyl benzimidazolium hydrogen sulphate [HMBIM]HSO _(4) were synthesized. Their physicochemical properties were investigated using spectroscopic and thermal techniques, including UV-Vis, FT-IR, ~(1) H NMR, ~(13) C-NMR, mass spectrometry, and TGA. The ILs were immobilized on mesoporous silica gel and characterized by FT-IR spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller analysis, ammonia temperature-programmed desorption, and thermogravimetric analysis. [HMIM]HSO _(4) @silica and [HMBIM]HSO _(4) @silica have been successfully applied as promising replacements for conventional catalysts for alkane isomerization reactions at room temperature. Isomerization of n -heptane and n -octane was achieved with both catalysts. In addition to promoting the isomerization of n -heptane and n -octane (a quintessential reaction for petroleum refineries), these immobilized catalysts are non-hazardous and save energy.