Efficient removal of trace olefins in aromatics by novel acetamide-based acidic deep eutectic solvents

The alkylation of olefins with aromatics (AOA) is considered an attractive method for removing trace olefins from aromatics. The catalyst with appropriate acidity is an important feature to control the alkylation reaction. In this work, a series of innovative acetamide (AC)-based acidic deep eutectic solvents (ADESs) with different organic sulfonic acids as hydrogen-bond donors (HBDs) were synthesized and used in AOA. The formation mechanism of ADES was investigated utilizing FT-IR spectroscopy, 1 H NMR, and quantum chemistry calculations combined with the phase diagram. In addition, the factors affecting the removal of olefins were further studied. Under optimal conditions, the most effective ADES ([AC:2TfOH]) can achieve 100% olefin conversion, and it can still reach 90% after 8 cycles. Finally, the mechanism of ADES ([AC:2TfOH]) catalyzed alkylation of aromatics and olefins was first investigated and proposed by in-situ diffuse reflectance infrared spectroscopy ( in-situ DRIFT) and gas chromatography-mass spectrometry (GC–MS).