Efficient absorption of ammonia with hydroxyl-functionalized ionic liquids

Abstract

The efficient ammonia absorption capacities of hydroxyl-functionalized ILs are due to the strong hydrogen bonding between the N atom of NH3 and the H atom of the hydroxyl on cation.

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 , …”

“…Palomar et al studied Henry's law coefficients of NH 3 in 272 ionic liquids to screen the most appropriate ILs for NH 3 capture and the results showed that [choline][NTf 2 ] and [EtOHmim][BF 4 ] with good thermal stability performance exhibited the highest NH 3 absorption ability . Li et al studied the NH 3 absorption mechanism using hydroxyl‐functionalized ILs through the combination of experiments and theoretical calculation and found that the strong hydrogen bond interaction between NH 3 and the H atom of the hydroxyl group on the IL resulted in high NH 3 absorption capacity . 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.…”

“…26 Li et al studied the NH 3 absorption mechanism using hydroxyl-functionalized ILs through the combination of experiments and theoretical calculation and found that the strong hydrogen bond interaction between NH 3 and the H atom of the hydroxyl group on the IL resulted in high NH 3 absorption capacity. 27 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 28-31 and therefore further work was concentrated on the screening and designing of ILs with higher NH 3 capacity.…”

“…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. 27,31 All the ILs obtained were put into a vacuum drying oven at 328 K for more than 72 h to ensure that water contents of the ILs were lower than 800 ppm before use and water contents were measured by Mettler Toledo Coulometric KF titrator C20. The residual halide contents in the ILs were measured using a PXSJ-226 Series ion meter (INESA Scientific Instrument Co. Ltd) and found to be between 0.05 wt% (ILs with [NTf 2 ]anions) and 0.20 wt% (ILs with [NO 3 ]anions).…”

Dual‐functionalized protic ionic liquids for efficient absorption of NH3 through synergistically physicochemical interaction

“…However, these conventional ILs can hardly compete with the industrial absorbents only through physical interaction. Thus, Palomar et al and Li et al introduced hydroxyl group into the cations of ILs, and found that the NH 3 solubility in 1–2(−hydroxyethyl)‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EtOHmim][NTf 2 ]) can be up to 0.830 mol NH 3 mol –1 IL (40 °C, 127 kPa). Further, Li et al confirmed that the introduction of hydroxyl group can increase the NH 3 solubility by comparing the results of 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][NTf 2 ], 0.149 mol NH 3 mol –1 IL) and [EtOHmim][NTf 2 ] (0.549 mol NH 3 mol –1 IL) at 60 °C and atmospheric pressure.…”