Effective absorption of SO 2 by imidazole‐based PILs with multiple active sites: Thermodynamic and mechanical studies

Aminoalkyl organosilicon with dual chemical sites for SO2 absorption and analysis of site-specific absorption entropy and enthalpy

Wet flue gas desulfurization is widely used for its high efficiency, however, the low absorption capacity, high viscosity and poor thermal stability of absorbents remains an open question. Herein, a low viscosity and high thermal stability SO2 absorbent with dual interacting sites was synthesized by introducing phenyl into organic silicon. The thermal stability of 1,5-bis (diethylamino)- 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane (BADPS) is comparable to ILs, while its viscosity is much lower than that of ILs. For the first time, we use a variant of the pseudo-first-order reaction rate equation obtained the reaction rate constant and the saturation absorption capacity. In addition, the optimal absorption and desorption temperatures were obtained based on an objective function. Mostly importantly, the absorption enthalpy change (ΔH) and entropy change (ΔS) of BADPS absorption reaction show the highest absolute values of SO2 absorbents reported so far. These results indicated that the prepared amine alkyl organosilicon could serve as a promising desulfurizing agent with low-energy consumption.

Deep eutectic solvent-based blended membranes for ultra-super selective separation of SO2

SO2 is a major atmospheric pollutant leading to acid rain and smog. As a new generation of green solvents, deep eutectic solvents (DESs) have been widely investigated for gas capture. Nevertheless, studies on DES-based membranes for SO2 separation are yet minimal. Herein, we devised polymer/DES blended membranes comprising 1-butyl-3-methyl-imidazolium bromide ([Bmim]Br)/diethylene glycol (DEG) DES and poly (vinylidene fluoride) (PVDF), and these membranes were firstly used for selective separation of SO2 from N2 and CO2. The permeability of SO2 reaches up to 17480 Barrer (0.20 bar, 40 ºC) in PVDF/DES blended membrane containing 50 wt% of [Bmim]Br/DEG (2:1), with ultrahigh SO2/N2 and SO2/CO2 selectivity of 3690 and 211 obtained, respectively, far exceeding those in the state-of-the-art membranes reported in literature. The highly-reversible multi-site interaction between SO2 and [Bmim]Br/DEG DES was revealed by spectroscopic analysis. Furthermore, the PVDF/DES blended membrane was also able to efficiently and stably separate SO2/CO2/N2 (2.5/15/82.5%) mixed gas for at least 100 h. This work demonstrates for the first time that [Bmim]Br-based DESs are very efficient media for membrane separation of SO2. The easy preparation, low cost and high performance enable polymer/DES blended membranes to be promising candidates for flue gas desulfurization.

Cation functional group effect on SO2 absorption in amino acid ionic liquids

Introduction: The effect of the functional group of the cation on SO2 acidic gas absorption by some designed amino acid ionic liquids (AAILs) was studied. Methods: An isolated pair of glycinate anion and pristine imidazolium-based cation, as well as decorated cation functionalized by hydroxyl (OH), amine (NH₂), carboxylic acid (COOH), methoxy (OCH₃), and acetate (CH₃COO) groups, were structurally optimized by density functional theory (DFT) using split-valence triple-zeta Pople basis set. Results and Discussion: The binding and Gibbs free energy (ΔG_int) values of SO₂ absorption show the AAIL functionalized by the COOH group is the most thermodynamically favorable green solvent and this functional group experiences the closest distance between anion and captured SO₂ and vice versa in the case of cation … SO₂ which may be the main reason for being the best absorbent; in addition, the highest net charge-transfer amount of SO₂ is observed. Comparing the non-covalent interaction of the systems demonstrates that the strongest hydrogen bond between captured gas and anion, as well as π-hole, and van der Waals (vdW) interaction play critical roles in gas absorption; besides, the COOH functional group decreases the steric effect while the CH₃COO functional group significantly increases steric effect after absorption that declines the hydrogen bond.

SO2 Adsorption and Kinetics Analysis during Supported Triethanolamine Acetate Ionic Liquid Desulfurization

Ionic liquid desulfurization is an effective method for achieving green and circulating desulfurization. To overcome the negative impact of the high viscosity of ionic liquids on the desulfurization process, an economical and efficient supported ionic liquid-triethanolamine acetate ionic liquid/silica (TAIL/SiO₂) was prepared in this study. TAIL is synthesized using triethanolamine and acetic acid and subsequently loaded onto silica gel particles. The effects of the reaction temperature, humidity, silica particle size, and loading ratio on SO₂ adsorption are investigated using a fixed-bed reactor. The results indicate that the surface of the silica gel loaded with ionic liquid formed uneven spherical clusters, and the aggregate volume increased with an increase in the loading ratio. The TAIL/SiO₂ sulfur capacity could be effectively increased by increasing the loading ratio (exceeding 0.74 is unfavorable), decreasing the silica particle size, and reducing the reaction temperature and moisture content. The maximum sulfur capacity can reach 124.98 mg SO₂/(g TAIL/SiO₂) under experimental conditions, which is higher than that of activated carbon. The Bangham rate model effectively predicts the kinetics of the adsorption process of SO₂.

Relationship between Structure and Properties of Nonstoichiometric Protic Ionic Liquids: n-Butylammonium Butyrate System

Nonstoichiometric protic ionic liquids have drawn much attention in applications, including fuel cells, batteries, and reaction media. An understanding of the relationship between their structure and properties is instructive for further applications. However, there are only a few studies on nonstoichiometric protic ionic liquids. Herein, the density, viscosity, and conductivity of nonstoichiometric n-butylammonium butyrate protic ionic liquids were measured, and we used small/wide-angle scattering (S/WAXS), electron paramagnetic resonance (EPR), and molecular dynamics (MD) simulation to explore the effect of mesostructure on their properties. It is found that the hydrogen bonds drive excess N-butyric acid (PrCOOH) molecules to wrap around ion clusters, resulting in the higher density and viscosity of PrCOOH-rich PILs. The microenvironments around various radicals differ significantly in BuNH₂-rich and PrCOOH-rich PILs because of the distinct molecular arrangements. This research provided a link between the physicochemical properties and structures of nonstoichiometric PILs, which is essential for their applications in electrolytes and organic reactions.