Efficient Absorption of SO₂ by [Emim][Cl]–[Emim][SCN] Ionic Liquid Mixtures

Abstract

The SO 2 absorption capacities of two ionic liquid mixtures formed by 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) and 1-ethyl-3-methylimidazolium thiocyanate ([Emim][SCN]) were studied. The ionic liquid mixtures with different molar ratios of [Emim][Cl] and [Emim][SCN] (1:1 and 1:2) can be easily synthesized. The SO 2 solubility in the two mixtures was investigated under different conditions. The results demonstrated that these mixtures were efficient for SO 2 absorption. [Emim][Cl]−[Emim][SCN](1:1) captured 0.50 g/g solvent at 20 °C and 0.10 atm. Under the low SO 2 partial pressure (1960 ppm), the [Emim][Cl]−[Emim][SCN](1:1) could capture 0.11 g/g solvent. The high SO 2 absorption capacity is mainly due to the strong charge-transfer interaction of the sulfur atom of SO 2 with the anions ([Cl] − and [SCN] − ). Moreover, the solvent [Emim][Cl]−[Emim][SCN](1:1) can be reused.

Bipyridinium-Based Ionic Covalent Triazine Frameworks for CO2, SO2, and NO Capture

“…The resonances at 170, 152, and 126 ppm indicated the existent of the triazine ring, bipyridine units, and aromatic carbon (Ar) atoms. Peaks appeared at 68.4–48.2 and 48.1–14.2 ppm were attributed to C on double bond and alkyl carbon, respectively. − For ICTF-SCN and the ICTF-Cl-SCN, the peak at approximately 132 ppm confirmed the peak of SCN – . In contrast, the characteristic peak of the triazine ring was diminished with the increasing partial graphitization of the samples. − …”

“…Based on the previous reports and the above discussion, the SO 2 absorption mechanism of ICTFs can be hypothesized (Scheme ). , …”

“…With the aid of abundant ionic groups, ILs have emerged as selective molecular recognition because there is a strong intermolecular interaction between SO 2 or NO and the functional groups . Amidst all the ongoing research efforts, ILs grafted with various functional ionic groups (−NH 2 , −COOH, and −OH) have been synthesized for flue gases adsorption/separation, that is, sulfur oxide (SO 2 ), nitrogen oxide (NO x ), and carbon oxide (CO X ). − Interestingly, the structural rearrangement of ILs can be observed after the adsorption of NO or SO 2 , which relies on the exchange of anions. , However, ILs endowed with high viscosity and poor shape plasticity have difficulty separating SO 2 in the actual atmospheric environment. Therefore, porous materials with active ionic groups provide a way for the design of high-selectivity adsorbents .…”

Development of SO2 Phase Change Absorption: Viscosity Change and Component Distribution Rules

“…At low SO 2 partial pressure, the capacity of DMEA is also much higher than those of other absorbents. For example, it is 0.87 g SO 2 /g DMEA at 0.2 atm, while the capacity of absorbent [Emim]­[Cl]­[SCN] is only 0.69 g SO 2 /g absorbent, which was considered to be an excellent absorbent in a previous work . Thus, to the best of our knowledge, DMEA has the highest gravimetric absorption capacity for SO 2 .…”

Investigation of Amine-Based Ternary Deep Eutectic Solvents for Efficient, Rapid, and Reversible SO2 Absorption

“…Millions of tons of sulfur dioxide (SO 2 ), mainly originating from the combustion of fossil fuels, are emitted per year. − The excessive emission of SO 2 could induce a series of environmental issues and would be harmful to people’s health. − Thus, the effective capture of SO 2 has received constant attention in recent decades . Traditionally, flue gas desulfurization methods are considered as the most reliable strategy, including the lime–limestone scrubbing method and ammonia scrubbing method. − However, tons of low-grade gypsum wastewater would be produced simultaneously with these methods, causing secondary pollution and further treatment . Besides, the absorbents used above are hard to be reused for the next run.…”