Spectroscopic analysis of acetamide-AlCl3-based ionic liquid analog and their catalytic performance in isobutene oligomerization

Abstract

The spectral structures of acetamide-AlCl3-based ionic liquid (IL) analogs were determined in detail through IR, NMR, and Raman spectroscopy. IR spectroscopy showed that 0.65AA-1.0AlCl3 was the coordination structure of Al and O atoms because of the resonance structure of acetamide. The mutual verification of the results of 27Al NMR and 1H NMR indicated that acetamide coexisted mainly in the form of cationic Al species and molecular Al species in xAA-1.0AlCl3, and AA/AlCl3 molar ratio affected the transformation of cationic Al species to molecular Al species. xAA-1.0AlCl3 was used as a green acidic catalyst for isobutene oligomerization, and the effects of AA/AlCl3 molar ratio, reaction temperature, reaction time, and volumetric ratio between IL analog and isobutene on product distribution were investigated. Optimal reaction conditions were AA/AlCl3 molar ratio of 0.75, reaction temperature of 60 °C, reaction time of 30 min, and catalyst/i-C4= volumetric ratio of 1.4 v/v. Under optimal conditions, isobutene conversion, (C8= + C12=) selectivity, (C16= + C20=) selectivity, and by-product selectivity were 85.26, 80.20, 6.80, and 13.00 wt%, respectively.

Keywords

• Oligomerization
• Isobutene
• Ionic liquid analog
• Catalytic performance