An Overview of Ammonia Separation by Ionic Liquids

Abstract

Ammonia (NH3) is an important chemical in several fields, such as agriculture, pharmaceutical, material, and chemicals manufacturing. However, NH3 is a toxic gaseous pollutant and NH3 release results in environment pollution. Minimizing NH3 emission is of great significance for solving NH3-related environmental issues and promoting the reuse of NH3 resources. Ionic liquids (ILs) are energy-saving gas absorbents, because of their low vapor pressure, good chemical stability, and high NH3 solubility. The recent research progress of conventional, functionalized ILs and novel IL-based materials and solvents for NH3 separation was summarized. The effects of anions and cations on NH3 absorption capacity, as well as the absorption mechanism of ILs, were discussed in detail in this Review. The simulated dynamic parameters of NH3–IL systems including mass diffusivity, heat- and mass-transfer coefficient were also discussed. In addition, this Review summarized the industrial application achievement of ILs in NH3 separation and recovery from NH3-containing tail gas, which spans from simulation, pilot plant to industrial applications. Finally, the research trends in NH3 separation by IL-based systems were proposed based on existing research.

Deep Eutectic Solvents Composed of Urea and New Salts of a Choline Family for Efficient Ammonia Absorption

“…Table collects the absorption capacities of NH 3 calculated from H m (0) at 313.15 K for the DESs obtained in this work and other essential (mostly) ionic absorbents, the data of which are available from literature. In general, the data reflect an expected trend of a greater absorption capacity for the absorbents containing a greater amount of water . For example, [emim]Cl + Tetz ( w H 2 O = 8900 ppm) absorbs 4.66, ChCl/Res/Gly ( w H 2 O < 10000 ppm) absorbs 7.65, and EaCl + Res ( w H 2 O = 5200 ppm) absorbs 9.00 mol of NH 3 by 1 kilo of a DES.…”

“…Many attempts have been implemented for the development of high-capacity, low-cost, reversible, and eco-friendly absorbents/adsorbents. These include metal hydrides, halides and borohydrides, porous materials with zeolites and carbon, activated aluminum, metal–organic frameworks, , porous organic polymers, supported metal halide sorbents ionic liquids (ILs), , deep eutectic solvents (DESs), , and so on . The concept of DESs as effective absorbents for gases of different natures arose at the end of the 2000s due to the unique combination of their properties.…”

Remarkable NH3 absorption in metal‐based deep eutectic solvents by multiple coordination and hydrogen‐bond interaction

“…As for the application of ILs in the elimination of NH 3 , the eliminated NH 3 can thus be recycled from ILs to act as the feedstocks for the production of a wide range of valuable products. There have been many ILs enabling efficient and reversible absorption of NH 3 reported in the literature, which are basically achieved by constructing hydrogen‐bond interaction and/or acid–base interaction between ILs and NH 3 25–28 . However, most of these ILs are with high cost due to the use of expensive reactants and/or complicated synthetic routes.…”

“…There have been many ILs enabling efficient and reversible absorption of NH 3 reported in the literature, which are basically achieved by constructing hydrogen-bond interaction and/or acid-base interaction between ILs and NH 3 . [25][26][27][28] However, most of these ILs are with high cost due to the use of expensive reactants and/or complicated synthetic routes. The use of solvents for the synthesis of ILs is also a drawback that is unfavored from the perspective of green chemical engineering.…”

Molecular insight into the effect of ion structure and interface behavior on the ammonia absorption by ionic liquids

“…13,14 The protic ILs were developed for NH 3 absorption and separation due to easy synthesis, high NH 3 solubility and selectivity, excellent recyclability, low viscosity and so on. Based on these studies, taking ILs as an absorbent, the new technology of IL-based NH 3 separation and recovery is used in industries of ammonium molybdate process 15 and melamine process. 16 Nevertheless, most ILs are hydrophilic, and even hydrophobic ILs also have hygroscopicity to some extent, which has a great impact on the performance.…”