Protic ionic liquid [Bim][NTf₂] with strong hydrogen bond donating ability for highly efficient ammonia absorption

Abstract

The capacity of NH3 in PIL [Bim][NTf2] was up to 2.69 mol NH3 per mol IL under ambient conditions.

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

“…Imidazolium‐based ILs including 1‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([Mim][NTf 2 ]), 1‐ethylimidazolium bis(trifluoromethylsulfonyl)imide ([Eim][NTf 2 ]), 1, 2‐dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([Mmim][NTf 2 ]), 1‐butylimidazolium bis(trifluoromethylsulfonyl)imide ([Bim][NTf 2 ]), 1‐butylimidazolium thiocyanide ([Bim][SCN]), 1‐butylimidazolium nitrate ([Bim][NO 3 ]), 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][NTf 2 ]), 1‐butyl‐3‐methylimidazolium thiocyanide ([Bmim][SCN]), 1‐butyl‐3‐methylimidazolium dicyandiamide ([Bmim][DCA]), 1‐butyl‐2, 3‐dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmmim][NTf 2 ]), 1‐butyl‐2, 3‐dimethylimidazolium thiocyanide ([Bmmim][SCN]), 1‐butyl‐2, 3‐dimethylimidazolium dicyandiamide ([Bmmim][DCA]) were synthesized through an anion exchange method using [Bim][Cl], [Eim][Cl], [Mmim][Cl], [Bmim][Cl], [Bmmim][Cl] and the corresponding salts, sodium thiocyanate (NaSCN), sodium nitrate (NaNO 3 ), sodium dicyandiamide (NaDCA) and lithium bis(trifluoromethylsulfonyl)imide (LiNTf 2 ). ILs with halogen anions purchased from Linzhou Keneng Material Technology Co., Ltd (purity >97%) were pretreated with ethyl acetate three times and the detailed synthesis process followed our previous work , …”

“…The solubility of NH 3 in ILs was measured using vapor liquid equilibrium (VLE) apparatus as shown in Fig. , as had been used in previous work , . The system was composed of a cylinder, a gas reservoir, an absorption cell, a vacuum pump, pressure sensors and valves.…”

“…A series of pressure–temperature ( p–T ) data were obtained and the equation of state (Peng–Robinson ( PR ) equation) as shown in Equation and Equation , was introduced to calculate the amount of gases in the gas phase of the two vessels (legitimately assuming that IL in the gas phase was negligible) . Therefore, the solubility of NH 3 in the ILs could be determined.…”

“…In fact, NH 3 would not be found alone in exhaust gases or process gases and the gases coexisting with NH 3 might include N 2 , O 2 , H 2 , CH 4 and so on. In general, the solubility of these nonpolar gases in ILs was several orders lower than that of NH 3 and therefore further work was concentrated on the screening and designing of ILs with higher NH 3 capacity.…”

“…In our previous work, we proposed the use of protic ionic liquid [Bim][NTf 2 ] with strong hydrogen bond donating ability for highly efficient NH 3 absorption, and obtained NH 3 solubility up to 2.69 mol NH 3 mol ‐1 IL at 313 K, 100 kPa. The possible absorption mechanism was that the protic hydrogen attached to the nitrogen could absorb about 2 mol NH 3 . In order to systematically study the effect of the structures of cations and anions of the protic ILs on NH 3 solubility, in this work, more imidazolium‐based protic and conventional ILs were synthesized and characterized (ESI) and the NH 3 solubility in these ILs was measured.…”