Synthesis of carboxymethylpyridine task-specific ionic liquid under ultrasonic irradiation

Task-specific ionic liquid N-carboxymethylpyridine hydrosulphate [CH₂COOHPy]HSO₄ was synthesized respectively with general method and associated with ultrasonic irradiation method. The structure of the synthesized ionic liquid was characterized by means of FT-IR, ¹H-NMR, ¹³C-NMR and the effects of the ultrasonic parameters on the yield of the ionic liquid were investigated. The results reveal that, compared with general method, the preparation of ionic liquid with ultrasonic irradiation method features simple operation, mild condition, short reaction time and higher yield. Under the ultrasonic irradiation of 500 W and 40 kHz, the yield of the intermediate product reaches 95.8% when reaction time was 2.5 h. Furthermore, the ionic liquids synthesized under ultrasound show light color, less impurities, and good performance in the extraction-oxidation desulfurization of model oil. It is attributed to that ultrasonic irradiation obviously improves the reaction selectivity.