Solubilities Of SO2 Research Articles

Rich Ether-Based Protic Ionic Liquids with Low Viscosity for Selective Absorption of SO2 through Multisite Interaction

Four low-viscosity protic ionic liquids (PILs) with the tertiary amine and rich ether skeletons are designed for selective absorption of SO2. To evaluate the selective absorption of SO2 by these PILs, the solubilities of SO2, CO2, and H2S are measured in the temperature range of 303.2–333.2 K and pressures up to 120 kPa by a volumetric method, respectively. The absorption of SO2 by [TMEA][MOAc] at 303.2 K and 101.3 kPa was found to be 10.424 mol·kg–1 (4.310 mol·mol–1), and the ideal selectivity of SO2/CO2 was 86.83. In addition, the solubility data are fitted using a reaction equilibrium thermodynamic model to obtain thermodynamics parameters including Gibbs free energy change (ΔrGm), enthalpy change (ΔrHm, ΔphyHm, ΔchemHm), and entropy change (ΔrSm). The mechanism of SO2 absorption by [TMEA][MOAc] is also investigated by FTIR and NMR analyses. Mechanistic and thermodynamic studies suggest that the high SO2 absorption is attributed to the O–SO2 multisite physical interaction. These ether-rich PILs are considered as a promising absorber because of their high SO2 solubility, good cycling performance, and low viscosity before and after absorption.

Densities and viscosities of, and solubilities of acidic gases (SO2 and H2S) in natural deep eutectic solvents

Natural deep eutectic solvents (NADESs) are a subcategory of deep eutectic solvents (DESs) consisting solely of natural compounds. They can replace existing DESs that contain toxic compounds and are difficult to dispose of in many applications. However, the detailed physical properties data of NADESs are still very scarce in the literature. In this work, a series of NADESs with choline chloride (ChCl) as the shared hydrogen-bond acceptor (HBA), and five dicarboxylic acids (oxalic, malonic, maleic, malic and tartaric) as the varied hydrogen-bond donors (HBDs) were prepared. The densities and viscosities of prepared NADESs were determined from 293.2 to 353.2 K at 1.013 bar. The densities and viscosities data were fitted using empirical equations. An important application of DESs is gas separation, which requires knowing the solubilities of gases in DESs. Therefore, a NADES with relatively good fluidity was selected out as a representative to determine the solubilities of two typical acidic gases (SO2 and H2S) in it. The solubilities of SO2 and H2S were determined from 298.2 to 333.2 K and from 0 to 1 bar. The SO2 and H2S solubilities data were fitted using the Krichevsky − Kasarnovsky equation.

Unexpectedly promoted SO2 capture in novel ionic liquid-based eutectic solvents: The synergistic interactions

A series of novel deep eutectic solvents (DESs) composed of equimolar solid ionic compounds (EmimX and EPyY; X, Y = Cl−, Br−) were developed for SO2 absorption in this work. Effects of absorption temperature, SO2 partial pressure, gas flow rate and moisture content on SO2 absorption capacities of the DESs were investigated. These DESs exhibited an extremely high SO2 loading capacity and excellent reversibility. Concretly, the solubilities of SO2 in 1-ethyl-3-methylimidazolium chloride (EmimCl)- N-ethylpyridinium chloride (EPyCl) were 1.483 and 0.777 g SO2/g solvent under the SO2 partial pressure of 1.0 and 0.1 atm at 20 °C, respectively, which were the highest values to date under the same conditions. Furthermore, EmimCl-EPyCl exhibited a reasonable SO2 capacity of 0.193 g SO2/g solvent when the SO2 concentration in the feed gas was 2000 ppm. The absorption mechanisms based on the results of 1H NMR and DFT calculation indicated that the high SO2 absorption capacity was mainly attributed to the synergistic interactions of the two components in the DESs rather than a simple combination of the capacities of EmimCl and EPyCl.

Chemically tunable DILs: Physical properties and highly efficient capture of low-concentration SO2

As a successive work towards exploring suitable IL-based absorbents for SO2 absorption from flue gas, we developed a species of new dicationic ionic liquids (DILs) with the combination of ether-functionalized dication and N-heterocyclic anions. These dual-functionalized DILs possessed high thermal stability, low vapour pressure, and high SO2 capacity. The solubilities of SO2 in the DILs increased with declining of the temperature and elevating of the SO2 concentration. Notably, the available loading capacity of SO2 in DIL4 was up to 0.267 g SO2·(g DIL)-1 at 313.2 K when the concentration of SO2 in the feed gas was 2000 ppm, which was exceedingly significant for trapping SO2 from the flue gas with low content of SO2. The regeneration experiments demonstrated that the absorption capacities of SO2 in DIL4 kept unchanged after six successive cycles of absorption/desorption. The absorption mechanisms based on the results of 1H NMR, FTIR analysis and quantum chemical calculations indicated that both physical and chemical interactions between the SO2 molecules and DIL4 could be found in spite of different concentrations of SO2.

PH-Responsive and Buffering Macromolecule Aqueous Absorbent and Mathematic Model-Based Feasibility Evaluation for SO2 Capture

An organic macromolecule, poly(1-vinylimidazole), with an appropriate polymerization degree was proposed and mixed with water to form a novel aqueous absorbent for SO2 capture. This aqueous solution absorbent has the advantages of simple preparation, good physicochemical properties, environment-friendliness, high ability in deep removal of SO2, and excellent reusability. Moreover, pH-responsive behavior, pH buffering absorption mechanism, and their synergistic effect on absorption performance were revealed. The solubilities of SO2 in the absorbent were measured in detail, and the results demonstrated excellent absorption capacity and recyclability. Then, mathematic models that describe SO2 absorption equilibrium were established, and the corresponding parameters were estimated. More importantly, on the basis of model and experimental data, the absorption and desorption could maintain high efficiency within a wide operating region. In summary, this work provided a low-cost, efficient, and unique absorbent for SO2 capture and verified its technical feasibility in industrial application.

Physicochemical property and solubility of SO2 in glycerin derivatives

Physicochemical properties of density, viscosity and refractive index for two glycerin derivatives of glycerol formal (GF) and DL-1,2-isopropyli-deneglycerol (GAK) were characterized in the temperatures ranging from 288.15 to 338.15 K at atmospheric pressure. The temperature dependence of these properties was correlated with simple linear or Arrhenius equation. The volume expansivities (β), molar volumes (Vm), molar refractions (Rm), and free volumes (fm) have been calculated on the basis of density and refractive index data. The active energy of viscosity (Ea) was also determined. Furthermore, the solubilities of SO2 in GF and GAK were determined at temperatures between 293.15 and 323.15 K with 10 K intervals and pressure scope of (0–122.0) kPa using isochoric saturation method. Henry's constants and thermodynamic properties such as Gibbs free energy, enthalpy, and entropy of dissolution were derived from the solubility data. GAK demonstrated higher gravimetric solubilities of SO2 than GF. All the dissolving enthalpies were negative at each condition. The dissolution of SO2 was a spontaneous process.

Absorption of SO2 in Furoate Ionic Liquids/PEG200 Mixtures and Thermodynamic Analysis

Carboxylate ionic liquid (IL) and polyethylene glycol 200 (PEG200) mixtures are suitable for the absorption of acidic SO2 because of their unique properties. In the present work, tetraethylammonium furoate ([N2222][FA]) and choline furoate ([Ch][FA]) were blended with PEG200 to form 40 wt % ILs/PEG200 mixtures as SO2 absorbents. The solubilities of SO2 in these two ILs/PEG200 mixtures were measured at T = (303.15, 313.15, 323.15, and 333.15) K and pressure up to 1.2 bar. [N2222][FA]/PEG200 demonstrated the high SO2 absorption capacity of 7.224 mol per kg absorbent at 303.15 K and 1.0 bar. The chemisorption mechanism of SO2 by mixture was studied by Fourier transform infrared and nuclear magnetic resonance spectra, and the influence of cations on the SO2 absorption capacity was analyzed. Furthermore, the reaction equilibrium thermodynamic model was used to correlate the experimental data, and Henry’s law constant (H), reaction equilibrium constant (K0), and thermodynamic properties (ΔrGm0, ΔrHm0, and ΔrSm0...

Investigation of SO 2 solubilities in some biobased solvents and their thermodynamic properties

Solubilities of SO2 have been determined in four biobased solvents (BBSs) at temperatures between 293.15 K and 323.15 K with 10 K intervals and pressure scope of (0–120.0) kPa using isochoric saturation method. The BBSs were selected from butyl lactate (BL), glyceryl triacetate (GT), triethyl citrate (TEC), and acetyl triethyl citrate (ATEC). Henry’s constants and thermodynamic properties such as Gibbs free energy, enthalpy and entropy of dissolution were derived from the solubility data. The gravimetric solubilities of SO2 in BBSs were in the range of (0.07–8.52) mol.kg−1 and changed with the sequence of GT > BL > TEC ≈ ATEC. All the dissolution enthalpies were negative at each condition. The performances of SO2 absorption in these solvents were further compared with those in some ionic liquids as well as common absorbents. The results illustrated that present BBSs possessed the potentiality as SO2 absorbents due to their relatively large absorption ability, small absorption enthalpy, low toxicity, and biodegradability.

Solubilities of Dilute SO2 in the Binary System of Glycol and Dimethylsulfoxide

The solubility of SO2 in binary mixtures of ethylene glycol (EG) and dimethylsulfoxide (DMSO), a potential candidate for use as the scrubbing liquid for the absorption of SO2 from flue gas, are lacking in the literature. The paper presents solubility data of dilute SO2 in these inexpensive solvent mixtures at T = (303.15, 308.15, and 313.15) K and p = 122.66 kPa. The solubilities of dilute SO2 in the mixtures increases gradually with increasing concentration of DMSO and decreasing temperature. The solubility of SO2 is linearly proportional to the experimental pressure. Meanwhile, the Henry’s law constants (H x ), dissolution enthalpy changes, dissolution entropy changes, and dissolution Gibbs energy changes were also obtained from the solubility data of SO2 in the mixtures. The experimental results demonstrate that the binary system of EG and DMSO is a promising alternative in SO2 separation processes due to its excellent absorption and regeneration performance.

Solubility and thermodynamic properties of SO2 in three low volatile urea derivatives

The solubilities of SO2 in three dipolar aprotic urea diversities, 1,1,3,3-tetramethylurea (TMU), 1,3-dimethyl-2-imidazolidinone (DMI), and 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H)-pyrimidinone (DMPU) was measured at temperatures ranging from (293.15 to 323.15)K and pressure up to 120kPa. By correlating the solubility results with a reaction equilibrium thermodynamic model (RETM), Henry’s constants (Hm), reaction equilibrium constants (K°), and enthalpy (ΔHr) in the absorption process were obtained. The results indicate that the three solvents exhibit both strong physical and weak chemical interactions with SO2. Further comparison of the capture performance with ILs, deep eutectic solvents (DESs), and several organic solvents, DMI, DMPU and TMU are noted to be excellent absorbents for acidic SO2.

Solubilities and thermodynamic properties of SO2 in five biobased solvents

Five biobased solvents (BBSs) with high boil point, namely ethyl levulinate (EL), butyl levulinate (BL), dibutyl succinate (DBS), gamma-butyrolactone (GBL) and gamma-valerolactone (GVL), were applied in absorption of SO2. The solubilities of SO2 in the BBSs were determined at temperatures (293.15 to 333.15)K and pressures (0 to 120)kPa. Henry’s constant and thermodynamic properties (standard dissolution Gibbs energy, dissolution enthalpy, dissolution entropy) were further calculated according to the solubility data. The gravimetric solubilities in BBSs changed with the sequence of GBL>GVL>EL>BL>DBS. The solubility of SO2 and absorption enthalpy in present BBSs and other molecular solvents as well as ionic liquids (ILs) were systemically compared. The results illustrated that GBL and GVL possessed the potentiality to capture SO2 among all absorbents due to their relatively large solubility and low absorption enthalpy for SO2, biodegradability, low toxicity, inexpensive cost and low viscosity.

Solubilities of CO2, CH4, C2H6, and SO2 in ionic liquids and Selexol from Monte Carlo simulations

Monte Carlo simulations are used to calculate the solubility of natural gas components in ionic liquids (ILs) and Selexol, which is a mixture of poly(ethylene glycol) dimethyl ethers. The solubility of the pure gases carbon dioxide (CO2), methane (CH4), ethane (C2H6), and sulfur dioxide (SO2) in the ILs 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cnmim][Tf2N], n = 4, 6), 1-ethyl-3-methylimidazolium diethylphosphate ([emim][dep]), and Selexol (CH3O[CH2CH2O]nCH3, n=4, 6) have been computed at 313.15K and several pressures. The gas solubility trend observed in the experiments and simulations is: SO2>CO2>C2H6>CH4. Overall, the Monte Carlo simulation results are in quantitative agreement with existing experimental data. Molecular simulation is an excellent tool to predict gas solubilities in solvents and may be used as a screening tool to navigate through the large number of theoretically possible ILs.

Solubility Properties and Spectral Characterization of Dilute SO2 in Binary Mixtures of Urea + Ethylene Glycol

Solubilities of SO2 in binary mixtures of urea and ethylene glycol were determined by gas–liquid equilibrium experiments at the temperatures from (298.15 to 318.15 K) and 122.7 kPa, with SO2 partial pressure in gas phase in the range of (0 to 130) Pa. Henry’s law constants were calculated based on the solubility data. It indicated that the mixture with urea molality of 6.65 mol·kg–1 has the most desirable capacity. More than 90 % SO2 can be regenerated by bubbling N2 at 338.15 K. Density and viscosity data for the binary mixtures were also measured. In addition, UV, IR, and NMR experiments were conducted to investigate the interaction between ethylene glycol, urea, and SO2. The result demonstrated that SO2 can interact with the mixture by both the charge-transfer interaction between S (SO2)···N (urea) and the hydrogen bond between O (SO2)···H (ethylene glycol).

Experimental study and thermodynamical modelling of the solubilities of SO2, H2S and CO2 in N-dodecylimidazole and 1,1′-[oxybis(2,1-ethanediyloxy-2,1-ethanediyl)]bis(imidazole): An evaluation of their potential application in the separation of acidic gases

Exploring low volatile solvents for the capture of acidic gases is highly valued from the viewpoint of green chemistry. In this work, the solubilities of SO2, H2S and CO2 in two long-chain N-substituted imidazoles: N-dodecylimidazole (NDI) and 1,1′-[oxybis(2,1-ethanediyloxy-2,1-ethanediyl)]bis(imidazole) (Im2TEG) at different temperatures and pressures were determined systematically. It is shown that the absorption behaviour of SO2 in NDI and Im2TEG deviates strongly from the ideality. However, the absorption behaviour of H2S and CO2 in NDI and Im2TEG deviates only slightly from the ideality. Therefore, the solubility data of SO2 were correlated using the PR-NRTL model while the solubility data of H2S and CO2 were correlated with the Krichevsky–Ilinskara (K–I) equation. Thermodynamic parameters including the Henry's constants at infinitely dilute condition and the enthalpy of absorption were calculated from the thermodynamic modelling. The potential application of the two liquid solvents in the selective separation of acidic gases (i.e., SO2/CO2 and H2S/CO2) was evaluated by comprehensively considering the absorption capacity and ideal selectivity. The results were compared with other organic solvents and ionic liquids. It is revealed that NDI and Im2TEG are two promising solvents for the selective separation of acidic gases due to their high absorption capacity of SO2 and H2S and high selectivity of SO2/CO2 and H2S/CO2.

Comparative Study of the Solubilities of SO2 in Five Low Volatile Organic Solvents (Sulfolane, Ethylene Glycol, Propylene Carbonate, N-Methylimidazole, and N-Methylpyrrolidone)

Solubilities of SO2 in five selected inexpensive organic solvents with low volatility were measured at temperatures from 303.2 K to 333.2 K and pressures up to 120 kPa. The solvents include sulfolane (SUF), ethylene glycol (EG), propylene carbonate (PC), N-methylimidazole (NMI) and N-methylpyrrolidone (NMP). The obtained results indicated that the solubilities of SO2 in the five organic solvents followed the sequence NMI > NMP > SUF > PC > EG. The absorption isotherms of SO2 in SUF, EG, and PC showed ideal profiles, while those in NMI and NMP showed nonideal types. The Henry’s law constants of SO2 in SUF, EG, and PC in terms of molality were calculated by drawing linear fit between SO2 solubilities and SO2 partial pressures. The interactions of SO2 with NMI and NMP were examined through density functional theory (DFT) calculations, and the solvent–solute complex formations were illustrated. The experimental solubilities of SO2 in NMI and NMP were successfully correlated by a reaction equilibrium thermodynamic model (RETM) proposed based on the DFT calculations. Subsequently, Henry’s law constants, reaction equilibrium constants, and heat of complex formation were also calculated to evaluate the potential of applying these organic solvents in SO2 absorption. The performance of SO2 absorption in these organic solvents were further compared with that in ILs and results illustrated that NMI and NMP were good alternatives to IL for applying in SO2 absorption.

SO2 absorption in acid salt ionic liquids/sulfolane binary mixtures: Experimental study and thermodynamic analysis

Two new simple acid salt ionic liquids (ASILs), tetraethylammonium diglutarate ([N2222][diglutarate]) and dimethylethanolammonium diglutarate ([DMEA][diglutarate]) were synthesized and the ASILs/sulfolane binary mixtures containing 40wt% ASILs were prepared for SO2 absorption in this work. The SO2 absorption rate is found to be quite fast with an equilibrium time within 2min, due to the low viscosity of the mixtures. The solubilities of SO2 in the two binary mixtures were measured under the pressure range of 0–1bar and the temperature range of 303.15–333.15K and results demonstrate the binary mixtures could trap as much as 6.836–7.624mol SO2/kg absorbents at 1bar and 303.15K. The solubilities are 0.826–0.954mol SO2/kg absorbents at a pressure as low as 0.004bar, which is important for capturing SO2 from the flue gas with low content of SO2. Thermodynamic analysis based on a Reaction Equilibrium Thermodynamic Model (RETM) was used to calculate the Henry’s law constants, reaction equilibrium constants, chemical absorption capacity, physical absorption capacity and thermodynamic functions of SO2 absorption in the mixtures. The calculated absorption enthalpy are −53.73 and −47.15kJ/mol for the two binary mixtures, respectively. The ASILs/sulfolane binary mixtures are shown to be an attractive alternative to pure ILs to be applied in SO2 absorption due to the large absorption capacity and low absorption enthalpy, as well as the fast absorption rate.

Solubility of dilute SO2 in 1,4-dioxane, 15-crown-5 ether, polyethylene glycol 200, polyethylene glycol 300, and their binary mixtures at 308.15 K and 122.66 kPa

This work reports the solubility data of dilute sulfur dioxide in 1,4-dioxane, 15-crown-5 ether, polyethylene glycol 200 (PEG 200), polyethylene glycol 300 (PEG 300), and their binary mixtures at 308.15K and 122.66kPa with the SO2 partial pressure ranging between (7.35 and 118Pa). From the solubility data, Henry's law constants of SO2 in pure solvents were calculated. The results show that the solubilities of SO2 in these four solvents increase linearly with the enhancement of the equilibrium partial pressure of SO2 in the gas phase within the studied regions. Furthermore, the absorption of SO2 in pure 1,4-dioxane, 15-crown-5 ether, PEG 200 are typical physical processes, and the solubility of SO2 in the three solvents decreases in the order: 1,4-dioxane>15-crown-5 ether>PEG 200. But the SO2 absorption in PEG 300 is a physical process accompanied by a chemical process.

Properties of alkylbenzimidazoles for CO2 and SO2 capture and comparisons to ionic liquids

To date, few reports have been concerned with the physical properties of the liquid phases of imidazoles and benzimidazoles-potential starting materials for a great number of ionic liquids. Prior research has indicated that alkylimidazole solvents exhibit different, and potentially advantageous physical properties, when compared to corresponding imidazolium-based ionic liquids. Given that even the most fundamental physical properties of alkylimidazole solvents have only recently been reported, there is still a lack of data for other relevant imidazole derivatives, including benzimidazoles. In this work, we have synthesized a series of eight 1-n-alkylbenzimidazoles, with chain lengths ranging from ethyl to dodecyl, all of which exist as neat liquids at ambient temperature. Their densities and viscosities have been determined as functions of both temperature and molecular weight. Alkylbenzimidazoles have been found to exhibit viscosities that are more similar to imidazolium-based ILs than alkylimidazoles, owed to a large contribution to viscosity from the presence of a fused ring system. Solubilities of CO2 and SO2, two species of concern in the emission of coal-fired power generation, were determined for selected alkylbenzimidazoles to understand what effects a fused ring system might have on gas solubility. For both gases, alkylbenzimidazoles were determined to experience physical, non-chemically reactive, interactions. The solubility of CO2 in alkylbenzimidazoles is 10%–30% less than observed for corresponding ILs and alkylimidazoles. 1-butylbenzimidazole was found to readily absorb at least 0.333 gram SO2 per gram at low pressure and ambient temperature, which could be readily desorbed under an N2 flush, a behavior more similar to imidazolium-based ILs than alkylimidazoles. Thus, we find that as solvents for gas separations, benzimidazoles share characteristics with both ILs and alkylimidazoles.

Solubility of SO2 in Caprolactam Tetrabutyl Ammonium Bromide Ionic Liquids

To explore environmentally benign solvents for absorbing SO2, a series of caprolactam tetrabutyl ammonium bromide ionic liquids were synthesized, the solubilities of SO2 in which were measured at (298.2 to 403.2) K and atmospheric pressure. The solubilities of SO2 in these ionic liquids were 0.680 at 298.2 K and ambient pressure and decreased sharply as temperature increased and increased with the increasing mole ratio of caprolactam. A fifth-order polynomial was proposed and verified by experimental solubility data. The absorption and desorption of SO2 were practically reversible in the synthesized ionic liquids.

Hydroxyl Ammonium Ionic Liquids: Synthesis, Properties, and Solubility of SO2

To explore environmentally benign solvents for absorbing SO2, a series of hydroxyl ammonium ionic liquids (ILs) was synthesized and characterized, and the solubilities of SO2 in these synthesized ILs were determined. It was found that the solubilities of SO2 in these ILs at ambient pressure are quite high, for example, the solubility of SO2 in tri-(2-hydroxyethyl)ammonium lactate is 0.4957 mole fraction and decreases sharply as temperature increase. The absorption and desorption are practically reversible in the synthesized ILs. Comparing with the conventional absorbents such as calcium carbonate (CaCO3), calcium oxide (CaO), and sodium hydroxide (NaOH), the synthesized ILs show two advantages: one is that the ILs can be recycled and repeatedly used, another is that the absorbed SO2 can be reversibly released and recovered as a sulfur resource.