Dual‐functionalized protic ionic liquids for efficient absorption of NH<sub>3</sub> through synergistically physicochemical interaction
Lei Yuan, Xiangping Zhang, Baozeng Ren, Yingliang Yang, Yinge Bai, Lu Bai, Hongshuai Gao, Shaojuan Zeng
Abstract
Abstract BACKGROUND Ionic liquids have become promising media for the treatment of tail gases containing ammonia (NH 3 ), which causes serious environmental problems and threatens human health. RESULTS In this work, four dual‐functionalized protic ionic liquids (DPILs) [C n OHim]X ( n = 1, 2; X = [NTf 2 ] − , [BF 4 ] − , [SCN] − ) with both weak acidity proton and hydroxyl group were designed and synthesized for enhanced NH 3 separation. Among them, the maximum NH 3 molar solubility of 3.11 mol NH 3 mol –1 IL was achieved in [EtOHim][NTf 2 ] at 40 °C and atmospheric pressure, and the highest mass solubility of NH 3 could be 0.221 g NH 3 g –1 IL in [EtOHim][SCN]; this is the highest value of any absorbent ever reported under the same conditions. Not only superior NH 3 solubility, along with excellent selectivity of NH 3 /CO 2 (65) and NH 3 /N 2 (104), but also outstanding recyclability was exhibited in DPILs. CONCLUSIONS The highly efficient performance of NH 3 absorption by DPILs was ascribed to the synergistically physicochemical interaction between weak acidity proton, hydroxyl group and NH 3 , which was confirmed through both spectrum analysis and quantum chemical calculations. This work implied that DPILs have great potentials in NH 3 separation and recovery of NH 3 ‐containing tail gases. © 2020 Society of Chemical Industry