Enhanced NH₃ capture by imidazolium‐based protic ionic liquids with different anions and cation substituents

Abstract

Abstract BACKGROUND Ionic liquids have become potential absorbents to treat exhausted gases containing NH 3 , which threatens the living environment of human beings. RESULTS In this study, 10 kinds of protic and conventional ILs were synthesized and characterized and their densities, viscosities and thermal decomposition temperatures measured. The NH 3 solubility in ILs from the vapor liquid equilibrium (VLE) experiments revealed that the chain length of cations had little influence on the NH 3 solubility of the protic ILs because of the high NH 3 capacities in protic ILs resulting from protic hydrogen atom compared with conventional ILs. The 2‐H atom on the cation influenced the NH 3 solubility in both protic and conventional ILs with different trends as the pressure was increased. Considering the effect of anions with the same cation [Bim] + , the order of NH 3 solubility in protic ILs was [Bim][NTf 2 ] > [Bim][SCN] > [Bim][NO 3 ]. Dynamic absorption of NH 3 in [Eim][NTf 2 ] preliminarily revealed that the absorption was fast under ambient pressure and through 5 cycles of absorption and desorption, the NH 3 absorption ability remained stable. CONCLUSIONS The relationship between the NH 3 solubility and the structures of both protic and conventional ILs was revealed, indicating the protic ILs as an alternative material for the treatment of NH 3 ‐containing exhaust gases. © 2017 Society of Chemical Industry