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

Abstract

BACKGROUND Ionic liquids have become potential absorbents to treat exhausted gases containing NH3, 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 NH3 solubility in ILs from the vapor liquid equilibrium (VLE) experiments revealed that the chain length of cations had little influence on the NH3 solubility of the protic ILs because of the high NH3 capacities in protic ILs resulting from protic hydrogen atom compared with conventional ILs. The 2‐H atom on the cation influenced the NH3 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 NH3 solubility in protic ILs was [Bim][NTf2] > [Bim][SCN] > [Bim][NO3]. Dynamic absorption of NH3 in [Eim][NTf2] preliminarily revealed that the absorption was fast under ambient pressure and through 5 cycles of absorption and desorption, the NH3 absorption ability remained stable. CONCLUSIONS The relationship between the NH3 solubility and the structures of both protic and conventional ILs was revealed, indicating the protic ILs as an alternative material for the treatment of NH3‐containing exhaust gases. © 2017 Society of Chemical Industry

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

“…In our previous research, we have designed several functionalized ILs for NH 3 absorption, all of which exhibit high NH 3 solubility . However, as most of these ILs absorb NH 3 efficiently through a single functionalized site, a new strategy by simultaneously introducing two or more functionalized sites into ILs was proposed.…”

Alkylimidazolium Protic Ionic Liquids: Structural Features and Physicochemical Properties

“…MeHIm cation: Ac [58] < F [58] < TFA [58] < MsO [5] < HSO 4 < TFSI [5] < TfO; [56] EtHIm cation: MsO [9] < BF 4 [8] < TfO < TFSI; [4] BuHIm cation: NO 3 [11] < TFA [5] < H 2 PO 4 [5] < MsO [9] < TfO [5] < HSO 4 [75] < TFSI; [80] HIm cation: TFA [74] < BF 4 [49] < MsO [48] � TfO < TFSI. [6,7] Since there are not enough experimental data, it is impossible to make a similar series for the salts with a PrHIm cation.…”

“…The glass transition temperatures of the protic (Table 4) and aprotic (Table S6 in ESI) ionic liquids with the same radical and anion are close to each other. The anion type has a more HIm 375 [48] 308.4(T b ) [49] 375 this work 379** [6,7] ~240 [74] 363.2 [49] MeHIm 333 65[55] 345 this work 382 85[75] 258**5 323.5 59[49] 343**5 391.5 66[56] ~400 86[76] 435.2 67[57] 328 (T start ) [11] 340.7 [4] 370**[5] 391 [77] 420 [78] 220 [58] 160 [58] 172** [5] 255 [58] 387 [49] 137* [62] 152.5 [63] EtHIm 252*[9] ~100 [79] 349* [9] 370 [8] 370.6 [57] 377 this work 300 [68] 317 (T start ) [11] ~350 [66,69] 385.3 [4] ~390 [19] 392.5 [67] 413 [8] 309 [8] PrHIm 335 this work 411 this work 399.2 [67] 410 this work…”

“…The data on the properties of aprotic alkylimidazolium ionic liquids are rather broadly presented in the literature but works on the PILs are sparse. [5][6][7][8][9][10][11][12] Although synthetic chemistry has remarkably accelerated the generation of ionic liquids, most researchers are interested in a priori forecasting of what type of species will form when selected bases and acids interact with each other: a salt, a molecular complex or an acid/base mixture. [13][14][15] To evaluate the extent of the acid-to-base proton transfer, the ΔpK a parameter (ΔpK a = pK a of the base-pK a of the acid) is frequently used.…”

110th Anniversary: The First Thermodynamic and Kinetic Analysis of Ammonia in Imidazolium-Based Ionic Liquids Using a Gravimetric Microbalance

“…In addition to aprotic ILs, protic ILs have also been studied. 15,16 Shang . 15 Also, contrary to aprotic ILs, the cation chain length for protic ILs was found to have little effect on the NH 3 solubility; however, fluorinated anions such as [NTf 2 ] had higher NH 3 absorption compared to nonfluorinated anions [SCN] and [NO 3 ].…”