Solubility Of SO2 Research Articles

SO2 crossover flux of Nafion® and sFS-PBI membranes using a chronocoulometric (CC) monitoring technique

Abstract A chronocoulometric electrochemical measuring technique was used to evaluate the gas flux and permeation properties of sulphuric acid dissolved SO2 across various polymeric membranes, using an in-house assembled permeation setup. This was done in the temperature and differential pressure range of 298–353 K and 0–2 bar respectively. The sulphuric acid concentration was varied between 30 and 90 wt%. The electrochemically measured current due to SO2 oxidation at the platinum electrode was converted to molar gas flux using Faraday's law. The flux was found to decrease as the temperature increased for all the evaluated membranes for example from 2.16×10−8±0.15 mol s−1 cm−2 at 298 K to 1.46×10−8±0.15 mol s−1 cm−2 at 353 K for Nafion® 112. The flux was found to increase with increasing Δp across the membrane and decrease with increasing acid concentration. From the flux data we were able to calculate the SO2 permeation, diffusion and solubility parameters for the various membranes.The measured and calculated values were compared to existing literature values. The lowest SO2 crossover was observed at high temperatures, low differential pressures and high H2SO4 concentrations.

Poly(amide-6-b-ethylene oxide) membranes for sour gas separation

In this paper, poly(amide-6-b-ethylene oxide) (PEBA1657) copolymer was used to prepare polyetherimide (PEI)/PEBA1657 composite membranes and ultra thin multilayer PEI/polydimethylsilicone (PDMS)/PEBA1657/PDMS composite membranes by dip-coating method for sour gas capturing. The gas permeation and transport characteristics of sour gases (CO2, H2S, and SO2) are investigated and analyzed. With the increase of transmembrane pressure difference, the permeation of H2S, CO2, and SO2 is enhanced due to pressure-induced plasticization effect. The temperature dependency of H2S permeance for PEI/PEBA1657 composite membranes changes from positive to negative when the transmembrane pressure difference increases from 3 to 7atm. However, the SO2 permeance of PEBA1657 composite membranes decreases dramatically with temperature increasing due to the reduction of SO2 solubility. By analyzing the difference of transport characteristics between PEI/PEBA1657 and PEI/PDMS/PEBA1657/PDMS composite membranes, PEI/PEBA1657 composite membranes with high SO2/N2 selectivity are preferred for SO2/N2 separation; while the multilayer PEI/PDMS/PEBA1657/PDMS composite membranes, displaying high permeances for CO2 and H2S, are suitable for CO2/N2 and H2S/N2 separation.

Efficient capture of SO 2 by a binary mixture of caprolactam tetrabutyl ammonium bromide ionic liquid and water

The solubility of SO 2 in a binary mixture of water and caprolactam tetrabutyl ammonium bromide ionic liquid (CPL-TBAB IL) was investigated. Though the ionic liquid and water were fully miscible, a phase separation occurred when SO 2 was introduced into the mixture. The SO 2 concentrated in the lower layer, and it could be released by heating the solution under reduced pressure (382.2 K, 10.1 kPa). After desorption, the mixture could be reused to absorb SO 2. It was found that SO 2 acts as a switch to cause the water and CPL-TBAB IL to phase separate, and the mechanics of this phase separation process was studied by gas chromatography–mass spectrometry, fourier transform-infrared spectroscopy and Karl–Fisher titration. The absorption and desorption of SO 2 in the CPL-TBAB/water mixtures were reversible.

Solubilities and Thermodynamic Properties of SO2 in Ionic Liquids

Task-specific ionic liquids (TSILs) have been experimentally demonstrated to absorb more sulfur dioxide (SO(2)) than normal ILs from gas mixtures with low SO(2) concentrations; however, the differences of SO(2) solubilities in the two kinds of ILs at given temperatures and pressures have not been studied systematically. Moreover, the mechanism of the interaction between SO(2) and ILs still remains unclear. In this work, the solubilities of SO(2) in TSILs (1,1,3,3-tetramethylguanidinium lactate and monoethanolaminium lactate) and normal ILs (1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate) were determined. The solubilities of SO(2) are correlated by a modified Redlich-Kwong equation of state (RK EoS). The chemical absorption and physical absorption are differentiated, and the absorption mechanism has been proposed with the aid of the modified RK EoS. SO(2) absorption capacity in TSILs is contributed from both chemical interaction and physical interaction. Two TSIL molecules chemically absorb one SO(2) molecule, and the chemical absorption amount follows the chemical equilibrium. Normal ILs only physically absorb SO(2) following Henry's law. The chemical equilibrium constant, reaction enthalpy, Gibbs energy of reaction, reaction entropy, and Henry's law constant of SO(2) absorbed in ILs have been calculated. The present model can predict SO(2) absorption capacity for capture and SO(2) equilibrium concentration in IL for recovery.

Absorption of dilute sulfur dioxide in aqueous poly-ethylene glycol 400 solutions at T = 308.15 K and p = 122.60 kPa

Isothermal (gas + liquid) equilibrium (GLE) data at T = 308.15 K and p = 122.60 kPa are reported for the absorption of dilute SO 2 in various aqueous poly-ethylene glycol 400 (PEG) solutions, in which SO 2 partial pressures are in the range of (0.9 to 92) Pa. Measurements are carried out by a saturation method using a glass absorption apparatus, which was controlled at constant temperatures by a thermostatic circulation bath with a Beckmann thermometer. The GLE data were obtained with uncertainties within 0.02 K for temperature, 0.1 kPa for total pressures, 3% for SO 2 concentration in the gas phase, and 0.6% for SO 2 concentration in the liquid phase. The measurements show that the solubility of dilute SO 2 in the system of {PEG (1) + water (2)} increases with increasing PEG concentration in the mass fraction range of w 1 = (0.40 to 1.00), and the solubility of SO 2 in the system of {PEG (1) + water (2)} presents an extreme minimum at the mass fraction of w 1 = 0.40 of 190 mg · L −1 when SO 2 in the gas phase is designed at Φ SO 2 = 5 · 10 −4. The peculiarity of this work is used to provide important GLE data for the design and operation of the absorption and desorption process in flue gas desulfurization (FGD) with potential industrial application of the solutions containing PEG.

Ether-functionalized ionic liquids as highly efficient SO2 absorbents

Room temperature ionic liquids (RTILs), ether-functionalized imidazolium methanesulfonates, exhibit extremely high SO2 solubility, at least 2 moles of SO2 per mole of RTIL at 30 °C and at atmospheric pressure. The solubility of SO2 in these RTILs increases with increasing number of tethered ether oxygen atoms and also with the pressure rise. FT-IR spectroscopic and quantum mechanical calculation results show that such high SO2 solubility is originated from the combined interactions of SO2 with methanesulfonate anion and ether oxygen atom or atoms on the imidazolium ring. The absorbed SO2 gas can be readily and completely desorbed from the RTILs by heating at 100 °C in a N2 flow, thereby allowing the RTILs to be reused up to 5 cycles without loss of their initial capacity.

Behaviors of SO 2 absorption in [BMIm][OAc] as an absorbent to recover SO 2 in thermochemical processes to produce hydrogen

The solubility behavior of SO 2 in 1-butyl-3-methylimidazolium acetate ([BMIm][OAc]) was investigated. The solubility of SO 2 in [BMIm][OAc] was measured to be 0.6 in mole fraction at 50 °C in a stream of SO 2 gas. The desorption of SO 2 from [BMIm][OAc] was never completed, until the temperature was raised to 170 °C in a stream of N 2, indicating that the absorption of SO 2 is irreversible at the experimental condition. An in-situ IR study showed that acetate anion in [BMIm][OAc] transformed into acetic acid during the SO 2 absorption. After removing acetic acid at 170 °C by evacuation, the bands at 1210, 1045 and 850 cm −1 appeared in IR spectra. The bands at 1210 and 1047 cm −1 were assigned to S–O stretching mode of HOSO 2 − (an isomer of HSO 3 −) and the band at 885 cm −1 was assigned to the symmetric stretching mode of HO–S. FT-IR study suggested that acetic acid and most plausibly [BMIm][HOSO 2] were generated from the interactions of [BMIm][OAc] with SO 2 and adventitious water in feed gas and/or [BMIm][OAc] during absorption–desorption process. [BMIm][HOSO 2] recovered after removing acetic acid was found to be a new and reversible SO 2 absorbent with the SO 2 absorption capacity of 0.55 in mole fraction.

Hydroxyl ammonium ionic liquids synthesized by water-bath microwave: Synthesis and desulfurization

Water-bath microwave method was used for hydroxyl ammonium ionic liquids (ILs) synthesis to study the removal of sulfur dioxide (SO 2) from the flue gas. The results showed that the water-bath microwave method has some advantages of short reaction time and good yields. The synthesis of ethanolamine lactate ILs was fundamentally studied by an orthogonal experiment design (L 9(3 4)). Based on statistic analysis, it is revealed that the molar ratio of ammonium/acid is the most significant variable, and the optimized preparation conditions are under 338 K, wave power of 300 W for 30 min with the molar ratio 1:1.1 (ethanolamine vs. lactic acid). At the same condition, the yield of the other ILs was over 90% except dimethyl ethanolamine-based ILs. Results showed that the solubility of SO 2 in ethanolamine lactate ILs was 0.51 (mole fraction), higher than others. Ethanolamine lactate ILs was a better absorbent for SO 2. The optimal temperature for the absorption and desorption process were 298 and 363 K, respectively. The optimal desorption time was 60 min. It was also found that water-bath microwave can improve the release of the absorbed SO 2 from ILs.

Dissolution Potential of SO2 Co-Injected with CO2 in Geologic Sequestration

Sulfur dioxide is a possible co-injectant with carbon dioxide in the context of geologic sequestration. Because of the potential of SO2 to acidify formation brines, the extent of SO2 dissolution from the CO2 phase will determine the viability of co-injection. Pressure-, temperature-, and salinity-adjusted values of the SO2 Henry's Law constant and fugacity coefficient were determined. They are predicted to decrease with depth, such that the solubility of SO2 is a factor of 0.04 smaller than would be predicted without these adjustments. To explore the potential effects of transport limitations, a nonsteady-state model of SO2 diffusion through a stationary cone-shaped plume of supercritical CO2 was developed. This model represents an end-member scenario of diffusion-controlled dissolution of SO2, to contrast with models of complete phase equilibrium. Simulations for conditions corresponding to storage depths of 0.8-2.4 km revealed that after 1000 years, 65-75% of the SO2 remains in the CO2 phase. This slow release of SO2 would largely mitigate its impact on brine pH. Furthermore, small amounts of SO2 are predicted to have a negligible effect on the critical point of CO2 but will increase phase density by as much as 12% for mixtures containing 5% SO2.

Gas−Liquid Equilibrium Data for Sulfur Dioxide + Nitrogen in Diethylene Glycol + Water at 298.15 K and 123.15 kPa

Isothermal gas−liquid equilibrium (GLE) data have been measured for the system diethylene glycol (DEG) (1) + water (2) + SO2 (3) + N2 (4) at 298.15 K and 123.15 kPa and SO2 partial pressures in the range of (0.7 to 100) Pa. Measurements were carried out by a saturation method using a glass absorption apparatus, which was controlled at constant temperatures by a thermostatic circulation bath with a Beckmann thermometer. The GLE compositions were obtained with relative uncertainties within ± 0.6 % for SO2 concentration in the liquid phase and ± 3.5 % for SO2 mole fraction in the gas phase. The measurement showed that the system DEG (1) + water (2) in the mass fraction range of w1 = (0.60 to 1.00) decreased the solubility of SO2 and the system DEG (1) + water (2) in the mass fraction range of w1 = (0.00 to 0.60) increased the solubility of SO2. Compared with our previous work (Zhang, J. B.; Wei, X. H.; et al. J. Chem. Eng. Data 2008, 53, 2372−2374; Zhang, J. B.; Wei, X. H.; et al. J. Chem. Eng. Data 2009, DOI: 10.021/je900392e), the solubility of SO2 in pure DEG is 259 mg·L−1 when SO2 volume fraction in the gas phase is Φ3 = 5·10−4, which is higher than in pure ethylene glycol (EG, 128 mg·L−1) and lower than in pure poly(ethylene glycol) 400 (PEG 400, 1330 mg·L−1). The results of this work can be used to provide important GLE data for the design and operation of the absorption and desorption process in flue gas desulfurization (FGD) with potential industrial application of various PEG aqueous solutions.

Latitudinal variation in the multiphase chemical processing of inorganic halogens and related species over the eastern North and South Atlantic Oceans

Abstract. Volatile inorganic and size-resolved particulate Cl- and Br-species were measured in near-surface air over a broad range of conditions within four distinct regimes (European – EURO, North African – N-AFR, the Intertropical Convergence Zone – ITCZ, and South Atlantic – S-ATL) along a latitudinal gradient from 51° N to 18° S through the eastern Atlantic Ocean. Median dry-deposition fluxes of sea salt, oxidized N, and oxidized non-sea-salt S varied by factors of 25, 17, and 9, respectively, among the regimes. Sea-salt production was the primary source for inorganic Cl and Br. Acidification and dechlorination of sea salt primarily by HNO3 sustained HCl mixing ratios ranging from medians of 82 (ITCZ) to 682 (EURO) pmol mol−1. Median aerosol pHs inferred from HCl phase partitioning with super-μm size fractions ranged from ~3.0 for EURO to ~4.5 for ITCZ. Because SO2 solubility over this pH range was low, S(IV) oxidation by hypohalous acids was unimportant under most conditions. Simulations with a detailed multiphase box model indicated that BrCl photolysis and ClO + NO were the major sources for atomic Cl in all regimes. Simulated midday concentrations of Cl atoms ranged from 2.1×104 to 7.8×104 cm−3 in the ITCZ and N-AFR regimes, respectively. Measured particulate Br− (median enrichment factor = 0.25) was greater and volatile inorganic Br less than simulated values, suggesting that the halogen activation mechanism in the model overestimated Br-radical production and processing. Reaction with atomic Br was an important sink for modeled O3 (5% in EURO to 46% in N-AFR). Formation of halogen nitrates accelerated the oxidation of NOx (NO + NO2) primarily via hydrolysis reactions involving S aerosol. Relative to simulations with no halogens, lower NOx coupled with direct reactions involving halogens yielded lower steady state mixing ratios of OH (20% to 54%) and O3 (22% to 62%) and lower midday ratios of OH:HO2 (3% to 32%) in all regimes.

Gas−Liquid Equilibrium Data for the Mixture Gas of Sulfur Dioxide + Nitrogen with Poly(ethylene glycol) Aqueous Solutions at 298.15 K and 122.61 kPa

Isothermal gas−liquid equilibrium (GLE) data have been measured for the system SO2 + N2 + poly(ethylene glycol) (PEG 400) + water at 298.15 K and 122.61 kPa and SO2 partial pressures in the range of (0 to 122) Pa. Measurements were carried out by a saturation method using a glass absorption apparatus, which was controlled at constant temperatures by a thermostatic circulation bath with Beckmann thermometer. The GLE data were obtained with relative uncertainties within ± 2.5 % for SO2 concentration in the gas phase and ± 0.6 % for SO2 concentration in the liquid phase. The measurement showed that the addition of water into PEG decreased the solubility of SO2 compared with pure PEG. Compared with our previous work (Zhang, J. B.; Wei, X. H.; et al. J. Chem. Eng. Data 2008, 53, 2372−2374), the aqueous PEG 400 solutions present stronger solubility to SO2 than ethylene glycol (EG) aqueous solutions. The results of this work can be used to provide important GLE data for the design and operation of the absorption and desorption process in flue gas desulfurization (FGD) with potential industrial application of PEG 400 aqueous solutions.

Molecular Simulation and Regular Solution Theory Modeling of Pure and Mixed Gas Absorption in the Ionic Liquid 1-n-Hexyl-3-methylimidazolium Bis(Trifluoromethylsulfonyl)amide ([hmim][Tf2N

Monte Carlo simulations are carried out to compute the solubility of SO2, O2, and N2 in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]). Simulations are also used to compute the mixed gas isotherms for the mixtures CO2/O2, SO2/N2, and CO2/SO2. The pure gas isotherms agree well with available experimental data. For the mixtures CO2/O2 and SO2/N2, the simulations predict that the mixed gas solubilities are nearly ideal, with little enhancement or competition between the two solutes. This is contrary to published experimental studies, which found that in a gas mixture, CO2 enhances the solubility of the otherwise sparingly soluble O2 and that the poorly soluble N2 inhibits the solubility of the highly soluble SO2. For the SO2/CO2 mixture, it is found that the two gases absorb independently at low pressure but compete with one another at high pressure. An energetic analysis was performed for the different solutes in the ionic liquid. The van der Waals energy between the solutes and ionic liquid was greater than the electrostatic interactions, and the van der Waals interactions were roughly the same between the solutes and the two different ions. CO2 and SO2 interact more strongly with the anion than the cation due to stronger electrostatic interactions between the solute and the anion. N2 and O2 interact weakly with the ionic liquid and show little difference in interaction energy between the cation and anion. Regular solution theory (RST) was evaluated for its ability to predict pure and mixed gas isotherms. It was found that if RST was applied in a strictly predictive mode using experimentally derived parameters, solubilities of CO2 were underpredicted by a substantial margin.

Gas−Liquid Equilibrium Data for a Mixture Gas of Sulfur Dioxide + Nitrogen with Ethylene Glycol Aqueous Solutions at 298.15 K and 123.15 kPa

Isothermal gas−liquid equilibrium (GLE) data have been measured for the system SO2 + N2 + ethylene glycol (EG) + water at 298.15 K and 123.15 kPa and SO2 partial pressures in the range of (0 to 120) Pa. Measurements were carried out by a saturation method using a glass absorption apparatus, which was controlled at constant temperature by a thermostatic circulation bath with a Beckmann thermometer. The GLE data were obtained with relative uncertainties within ± 3.5 % for SO2 concentration in the gas phase and ± 0.6 % for SO2 concentration in the liquid phase. The measurement showed that the addition of water to EG enhanced the solubility of SO2 compared with pure EG and that the 80 % volume fraction of EG in ethylene glycol + water solution is a more reasonable composition used as the desulfurization solution. The results of this work can be used to provide important GLE data for the design and operation of the absorption and desorption process in flue gas desulfurization (FGD) with potential industrial application of EG aqueous solutions.

Removal of SO2 Using a Magnetically Fluidized Bed in the Semi‐Dry Flue Gas Desulfurization Process: Roles of Ferromagnetic Particles and Applied Magnetic Field in the Desulfurization Reaction

AbstractA new semidry flue gas desulfurization (FGD) process is proposed. The process uses a magnetically fluidized bed (MFB) as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. A slurry of lime is continuously sprayed into the reactor by an atomizer fixed at the top of the bed. As a consequence, the desulfurization reaction and slurry drying take place simultaneously in a same reactor. Experiments with a laboratory‐scale apparatus were carried out to investigate the roles of the ferromagnetic particles and the magnetic field applied in the desulfurization reaction. The results show that when ferromagnetic particles are used as the fluidization material, both sulfite (SO32–) salts and sulfate (SO42–) salts are found in the desulfurization products. When quartz particles are used, only sulfite (SO32–) salts are found. This suggests that the Fe(III) ions and Fe(II) ions result from the ferromagnetic particles dissolving in the liquid phase. In addition, the ions act as catalysts in the oxidation of S(IV) to S(VI) and react with SO2 producing FeSO3 and Fe2(SO4)3 as the products. On the other hand, the level of the sulfate (SO42–) salts in the products increases with increasing intensity of applied field intensity, which suggests that the oxidation of S(IV) can be enhanced by the applied magnetic field. The oxidation of S(IV) can increase the solubility of SO2, and therefore, intensify the reaction between SO2 and Ca(OH)2, leading to an increased SO2 removal efficiency.

Difference for SO2 and CO2 in TGML ionic liquids: a theoretical investigation

Quantum chemical calculations (QM) have been used to investigate the interaction between sulfur dioxide (SO(2)) or carbon dioxide (CO(2)) molecules and ions of 1,1,3,3-tetramethylguanidium (TMG) lactate (LAC) (TMGL) ionic liquid. The QM results give us a deeper understanding of the factors that govern the high solubility of SO(2) in TMGL and the difference in the solubility of SO(2) and CO(2) in TMGL. The predicted geometries and binding energies imply a strong organization of SO(2) about the TMGL components, especially the LAC anion; but indicate a relatively weak organization of CO(2). Both the SO(2) and CO(2) molecules can interact with the TMG cations forming a N-H...O interaction; however, the binding energies demonstrate that the interaction with CO(2) is weaker than that with SO(2). The theoretical results indicate that the oxygen atoms of the LAC anion are the main active sites for the absorption of SO(2). Strong SO interactions are found for both the SO(2)-LAC and SO(2)-TMGL complexes.

Force Field of the TMGL Ionic Liquid and the Solubility of SO2 and CO2 in the TMGL from Molecular Dynamics Simulation

An all-atom force field is developed using a combination of density functional theory calculations and OPLS force field parameter values for the 1,1,3,3-tetramethylguanidium lactate (TMG) lactic acid (LAC) ionic liquid (TMGL). The computed density of the TMGL is in good agreement with available experimental values. The internal energy components, cohesive energy density, and the self-diffusion constants are also discussed. Molecular dynamics simulations are then conducted to investigate the solubility of the SO2 and CO2 gases in the TMGL. The simulation results show strong organization of SO2 about the TMG cation and the LAC anion, especially the LAC anion, but relatively weak organization of CO2 about the cation and the anion of the TMGL, which explained well the selectivity of the TMGL toward the SO2 and CO2.

Solubility of SO2, CO2 in DMSO+Mn2+ mixture solvents and EOS model

The electrolyte equation of state (EOS) in [Phys. Chem. Liq., 44(1), 83, 2006] has been applied which describes the solubility of SO2 in DMSO + Mn2+ mixture solvents. With the assumptions used in previous applications of our model to SO2 system, the EOS in this study is extended to the system of SO2 and CO2. In this article, on the basis of solubility measurement of dilute SO2, CO2 in DMSO + Mn2+ mixture solvents, an extended EOS model is described. In order to test the correctness of our model, the data of gas–liquid equilibrium of such a multicomponent system have been fitted with the binary interaction parameters in the model, and the solubilities calculated by the model show good agreement with the experimental data.

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.

Solubility of SO2, CO2 in desulfuration solution from 293.15 to 313.15 K

The solubility of dilute SO2, CO2 gas mixture in desulfuration solution has been determined from 293.15 to 313.15 K, along with the partial pressures of SO2 from 0.15 to 3.0 kPa, and of CO2 from 5 to 18 kPa. The measured solubility data are useful in the process design of SO2 removal from flue gas.