Sulfolane Solvent Research Articles

Extraction process design for the separation of aromatic and aliphatic hydrocarbons using organic solvent, ionic liquid or their mixture: a comparative study

The goal of the present work is focused on the design of a liquid–liquid extraction process using organic solvent, ion liquids (IL), as well as their mixture. For this purpose, the sulfolane/[bmim][SCN] system was investigated. Benzene–heptane binary mixture has been selected as a case study representing aromatic and aliphatic hydrocarbon families, respectively. A comparative study among three proposed extraction processes employing the traditional organic solvent sulfolane, [bmim][SCN] and the system of sulfolane/[bmim][SCN] has been provided to determine the optimal process for benzene extraction. For feed containing less than 50 wt% of benzene, it was recommended to use a mixed solvent containing 60 wt% of [bmim][SCN].

Liquid Structure and Battery Application of Highly Concentrated Sulfolane-Based Sodium Electrolytes

Sodium is earth-abundant compared to lithium, and sodium ion battery has drawn much attention as an alternative battery system. We report here the physicochemical properties, solvation structure, and electrochemical properties of highly concentrated electrolytes composed of NaN(SO2F)2 (NaFSA) and sulfolane (SL) solvent for Na-ion batteries. Our group recently reported that highly concentrated Li electrolytes of SL show Li ion hopping conduction.1 In the highly concentrated lithium salt (LiX)/SL electrolytes, two oxygen atoms of SL were found to coordinate to different Li ions, forming extended chain-like Li ion coordination structures of -SL-Li+-SL- and -X--Li+-X--. In the highly concentrated electrolytes, Li ion exchanges ligands (solvent and anion), leading to the hopping-like Li ion conduction. The ionic size of Na+ is larger than that of Li+, and the Na+ ion has lower charge density compared with Li+. In this study, the effects of cation size on the physicochemical and electrochemical properties of SL-based electrolytes were investigated. We found that NaFSA and SL form a stable solvate at a molar ratio of 1:3. In the single crystal of NaFSA/SL = 1/3, two oxygen atoms of SO2 moiety of SL coordinate to two different Na ions. In addition, an oxygen atom of one SO2 moiety of FSA anion and an oxygen atom of another SO2 moiety coordinate to different Na ions as shown in Figure. At molar ratio of [NaFSA]/[SL] ≥ 1/1.6, the mixtures become glass forming liquids and keep liquid state at room temperature. Raman spectra for the liquids of [NaFSA]/[SL] ≥ 1/1.6 suggest that solvent-bridged structure (-SL-Na+-SL-) and anion-bridged structure (-FSA--Na+-FSA--) are formed even in the liquid state. Walden plot for [NaFSA]/[SL] ≥ 1/1.6 indicated that the ion conduction partially decoupled from the viscosity of the liquid. Molecular dynamics simulation suggested that Na+ ion diffuses faster than SL in the concentrated electrolytes. Battery tests of Na/hard carbon and Na/Na0.44MnO2 cells were carried out using an electrolyte of [NaFSA]/[SL] = 1/1. The cells showed stable charge-discharge behaviors, suggesting that the highly concentrated NaFSA/SL electrolyte possesses a wide electrochemical window and a potential application in Na-ion batteries. Reference 1. Dokko, K.; Watanabe, D.; Ugata, Y.; Thomas, M. L.; Tsuzuki, S.; Shinoda, W.; Hashimoto, K.; Ueno, K.; Umebayashi, Y.; Watanabe, M. Direct Evidence for Li Ion Hopping Conduction in Highly Concentrated Sulfolane-Based Liquid Electrolytes. J. Phys. Chem. B 2018, 122 (47), 10736–10745. Figure caption Figure. Crystal structure of NaFSA/SL = 1/3. Figure 1

Measuring Activity Coefficient at Infinite Dilution of Hydrocarbons in Ionic Liquids and Evaluation of Other Thermodynamic Properties using Gas Chromatography

Activity coefficients at infinite dilution (γi∞) offer a valuable tool for solvent selection in extraction processes. In this study, the γi∞ values for solutes like alkanes, aromatics, and naphthenes in solvents, i.e., ionic liquids N-butyl-4-methylpyridinium tetrafluoroborate [BMPy][BF4], 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMPyr][NTf2], and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], were estimated using gas–liquid chromatography at temperatures 313.1, 333.1, and 353.1 K. Partial molar excess enthalpies at infinite dilution (ΔH1E,∞) were evaluated from the γi∞ values. The selectivity for the toluene/n-heptane system was also calculated from the experimentally observed γi∞ and compared to the literature values for well-established industrial solvents sulfolane and N-methyl pyrrolidone.

Production of levulinic acid from glucose in sulfolane/water mixtures

Levulinic acid derived from biomass is a versatile platform molecule, which can be used in manufacturing different compounds to replace fossil-based chemicals. In this study, the effect of sulfolane as solvent in sulphuric acid catalysed levulinic acid production from glucose was investigated. The broad sulfolane concentration range was systematically studied and a kinetic model was developed to describe the levulinic acid production. A significant increase in glucose conversion rate was observed when the proportion of sulfolane in the solvent mixture was increased. The maximum selectivity of the levulinic acid production was found to be slightly over 50% and independent of the solvent composition. Thus, with sulfolane solvent, the same yields can be obtained in a significantly shorter time or at a lower temperature as when water is used as solvent. Sulfolane was also found to keep the generated by-products in soluble form. This will decrease fouling of the process equipment, which has been a major issue in designing of levulinic acid production processes.

CO2 Absorption Rate and Capacity of Semi-Aqueous Piperazine for CO2 Capture

Abstract Aqueous piperazine (PZ) is a representative second-generation solvent for flue gas amine scrubbing; however, the solid precipitation of aqueous PZ at lean loading needs to be addressed. Semi-aqueous piperazine composed of PZ, water, and a physical solvent (sulfolane or imidazole) has been characterized in a wetted wall column. No precipitation was observed in 5 m PZ in SUF/water or IMI/water in the loading range of 0.15–0.45 mol CO2/mole alkalinity at 20–60 °C. The average viscosity at 40 °C in this range is about 25 cP in 5 m PZ in 1SUF/1water, 9.5 cP in 5 m PZ in 1SUF/3water, and 15 cP in 5 m PZ in 1IMI/1water, greater than 4 cp in 5 m aqueous PZ. Adding SUF or IMI into aqueous PZ increases absorption rate (kg’) at lean and median loading but decreases kg’ at rich loading. kg’ in semi-aqueous PZ increases as temperature decreases from 60 to 20 °C. At 40 °C, kg’avg in 5 m semi-aqueous PZ is 15–35% greater for the operating range of 0.1–5 kPa P*CO2, and 20–50% greater for 0.1–1.5 kPa P*CO2 (natural gas conditions). CO2 cyclic capacity slightly increased after adding SUF or IMI.

Selective oxidation of methane to methanol with H2O2 over an Fe-MFI zeolite catalyst using sulfolane solvent.

The effect of reaction conditions for direct oxidation of methane to methanol over Fe-MFI zeolite with H2O2 has been investigated. Sulfolane has been proved to be an efficient solvent for liquid-phase methane oxidation. A sulfolane/water mixture with an appropriate proportion led to an extremely high methanol production with a high selectivity.

Liquid-liquid equilibrium for mixtures of hexadecane + xylenes + pyrene + solvent at 373.15 K

Liquid-liquid equilibrium tie line data were determined at 373.15 K for a model hydrocarbon mixture consisting of hexadecane + xylenes + pyrene with the solvents sulfolane and diethylene glycol (DEG), and also with the solvent combination N-methylpyrrolidone/ethylene glycol (NMP/EG). The measured data were used to estimate binary interaction parameters of the UNIQUAC model. All solvents presented comparable selectivities for pyrene relative to xylenes. Pyrene partition ratios greater than unity were observed for sulfolane only. As a result, from a selectivity/capacity viewpoint, when compared to NMP/EG and DEG, sulfolane is potentially the best suited solvent for extraction of pyrene. Selectivities greater than unity were observed for all solvents studied. Therefore, pyrene, a polycyclic aromatic hydrocarbon, can be selectively removed from oil containing monocyclic aromatic hydrocarbons such as xylenes.

Active Mechanism of the Interphase Film-Forming Process for an Electrolyte Based on a Sulfolane Solvent and a Chelato-Borate Complex

Electrolytes based on sulfolane (SL) solvents and lithium bis(oxalato)borate (LiBOB) chelato-borate complexes have been reported many times for use in advanced lithium-ion batteries due to their many advantages. This study aims to clarify the active mechanism of the interphase film-forming process to optimize the properties of these batteries by experimental analysis and theoretical calculations. The results indicate that the self-repairing film-forming process during the first cycle is divided into three stages: the initial film formation with an electric field force of ∼1.80 V, the further growth of the preformation solid electrolyte interphase (SEI) film at ∼1.73 V, and the final formation of a complete SEI film at a potential below 0.7 V. Additionally, we can deduce that the decomposition of LiBOB and SL occurs throughout nearly the entire process of the formation of the SEI film. The decomposition product of BOB- anions tends to form films with an irregular structure, whereas the decomposition product of SL is in favor of the formation of a uniform SEI film.

Simulated exergy and energy performance comparison of physical–chemical and chemical solvents in a sour gas treatment plant

A feasibility simulation study evaluates the utilization of the physical–chemical solvent Sulfolane plus Methyl di-ethanol amine (MDEA) plus H2O (Sulfinol-M), to replace the aqueous amine solvent (MDEA) currently used in the sour-gas treatment unit of the large-scale Khangiran gas processing plant (Iran). Physical–chemical solvents, such as Sulfinol-M, have the advantages over chemical solvents in that: (1) their absorption of pollutants is not limited by their stoichiometry; (2) they can be easily regenerated by reduction of pressure alone; and, (3) they demonstrate a strong capability to remove sulphur compounds. The simulation and exergy analysis of this gas treatment plant compare the performance of the currently used MDEA solvent with the Sulfinol-M solvent in various concentrations. The influences of different parameters, including inlet solvent temperature, composition and flow rate of solvents on the removal of H2S and CO2, together with associated exergy and energy losses are evaluated for the MDEA solvent and a range of concentrations of the Sulfinol-M solvent. The simulated exergy analysis demonstrates suitable absorption of acid gases by the Sulfinol-M solvent for less energy and cost than the MDEA solvent.

Regularities of ionic solvation and association of lithium difluoro(oxalate)borate in dimethyl carbonate and sulfolane solvent systems

Lithium difluoro(oxalate)borate (LiODFB) is acknowledged as a new type of electrolyte lithium salt with great potential for high-voltage lithium-ion batteries. Utilizing Raman spectroscopy, a conductivity tester, and a viscometer, this study concentrates on the solution structures and properties of LiODFB-solvent systems. The results demonstrated that in the sulfolane (SL) solvent, the main coordination form is among the Li+ cation. The ODFB− anion and SL molecules form an ionic solvation as a contact ion pair (CIP). The content of free Li+ cations is very considerable, which is beneficial to improve the solubility and conductivity of LiODFB in the SL solvent. In the dimethyl carbonate (DMC) solvent, the main coordination form is ionic association as an aggregate (AGG). In addition, the solvent can display the comprehensive superiority of the SL solvent and LiODFB salt when a high concentration is dissolved in the SL-DMC as a mixed solvent.

A Critical Evaluation of the Advanced Electrolyte Model

A fast and accurate method to obtain transport properties of electrolyte solutions for Li-ion batteries is of great interest for both screening potential electrolyte candidates and for use in physics-based models of Li-ion cells. The Advanced Electrolyte Model (AEM) considers various molecular-scale interactions in a chemical physics framework to calculate these electrolyte transport properties in a computationally inexpensive manner. Should these calculations match experiment well, the AEM would be an ideal tool for the rapid determination of transport properties for various electrolyte systems. This paper aims to evaluate the accuracy of the AEM against experimental viscosity and conductivity data for electrolytes of interest in lithium batteries. Recent measurements, as well as previous measurements of now-obsolete electrolyte systems, are compared to corresponding calculations from the AEM. The availability of accurate laboratory data has allowed for improved accuracy of the AEM theory, molecular parameters and related predictions of properties, in particular for certain systems with low concentrations of ethylene carbonate (i.e. low permittivity electrolytes), as well as systems containing the salt Li triflate or the solvent sulfolane. The model now provides accurate calculations for the transport properties of most of the different systems considered here.

High Octane Gasoline Using Renewable Aromatic Hydrocarbons

Background: The replacement of leaded high octane aviation gasoline with an unleaded renewable alternative would decrease the emissions of lead and fossil-derived carbon into the atmosphere. Replacement has been limited by the requirement of a very high octane number in many existing general aviation aircraft engines. Method: Two separate process pathways were developed that generate an unleaded octane fuel with a motor octane number >96 from triglyceride oils (TGs), such as crop oils and algae oil. A series of experiments coupled with process simulations was used to verify the feasibility of both pathways and to provide preliminary laboratory scale data that could form the basis for further development towards a commercial technology. In the first pathway, TG oil is catalytically cracked to produce a high concentration of simple aromatic hydrocarbons. These aromatic hydrocarbons are then alkylated using propylene to form a mixture, which after purification acquires fuel properties compliant with those in the ASTM specification for 100 octane low lead aviation gasoline (100LL AvGas). In the second process pathway, the aromatic hydrocarbons are isolated after cracking using a sulfolane solvent extraction process to increase alkylation efficiency and fuel quality. Result: The results demonstrate that it is technically feasible to produce a replacement for 100LL AvGas using either pathway, and thus these strategies may be attractive candidates for commercialization.

Search for liquids electrospraying the smallest possible nanodrops in vacuo

Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (Tb) solvents formamide (FM) and propylene carbonate (PC) (Tb of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse Isp varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ε = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ε = 8.9, μ = 3.4 cP), both with Tb > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high Isp. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF4, EMI-N(CN)2, and DMI-N(CN)2. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA+ cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.

On anodic stability and decomposition mechanism of sulfolane in high-voltage lithium ion battery

In this work, we investigated the anodic stability and decomposition mechanism of sulfolane (SL). The anodic stability of SL-based electrolyte with different lithium salts on Pt and LiNi0.5Mn1.5O4 electrodes was found to decrease as follows: LiPF6/SL>LiBF4/SL>LiClO4/SL. The oxidation potential of 1M LiPF6/SL electrolyte on both Pt and electrodes is about 5.0V vs Li/Li+. The presence of PF6- and another SL solvent dramatically alters the decomposition mechanism of SL. Oxidation decomposition of SL-SL cluster is the most favorable reaction in LiPF6/SL electrolyte. The dimer products with S-O-R group were detected by IR spectra on the charged LiNi0.5Mn1.5O4 electrode surface and in the electrolyte near the electrode surface, and were found to increase the interfacial reaction resistance of the LiNi0.5Mn1.5O4 electrode.

The effect of aqueous alcohols (methanol, t-butanol) and sulfolane on the dissociation constants and thermodynamic properties of alkanolamines

The dissociation constants of protonated monoethanolamine, N-methyldiethanolamine have been determined in aqueous mixtures of methanol, t-butanol–water and sulfolane solvents. The mole fractions of the organic compounds ranged from (0.2 to 0.95) and the temperatures from (283 to 353)K. Standard state thermodynamic properties like ΔrG, were derived from the results. The basic strength of the protonated alkanolamine decreased with decreasing dielectric constant and increase in temperature of the solvent.

Electrochemical performances of a novel high-voltage electrolyte based upon sulfolane and γ-butyrolactone

To seek the promising candidate for 5 V electrolytes, fluorine-free lithium bis(oxalato)borat (LiBOB) is chosen as the lithium salt, γ-butyrolactone (GBL) as well as sulfolane (SL) with the property of stability against oxidative decomposition is chosen as supporting electrolyte solvents, and linear diethyl carbonate (DMC) is chosen as the third supporting electrolyte solvent to lower viscosity. After systematical analytical studies, it indicates that SL solvent is the main and key reason for the improvement of electrochemical performance, which not only improves the stability of electrolyte system against oxidative decomposition, but also decreases the electrode polarization resistance. More than that, 1.0molL−1 LiBOB–SL/GBL/DMC electrolyte shows good compatibilities with both intercalation hosts as LiNi0.5Mn1.5O4 cathode and carbonaceous anode. It suggests that this novel electrolyte would be an alternative electrolyte for 5 V high-voltage rechargeable lithium-ion batteries based upon LiNi0.5Mn1.5O4 cathode.

Feasibility of Ionic Liquids as Extractants for Selective Separation of Vitamin D3 and Tachysterol3 by Solvent Extraction

A selective separation of vitamin D₃ and tachysterol₃ by solvent extraction with 7 organic solvents and 11 ionic liquids (ILs) has been reported. Among organic solvents sulfolane showed optimal extraction performance, giving only a selectivity of 1.44 for tachysterol₃ over vitamin D₃. ILs with unsaturated bonds demonstrated high selectivity probably due to their different π-π interactions with the two compounds. A pyrrolidinium-based ionic liquid, for example, [BMPr][NTf2], provided the highest selectivity up to 1.77. Acceptable selectivity and distribution coefficients were observed by a combination of organic solvents and ILs as extracting agents. In this work, the effects of concentrations, anions, cations, and substituent of ILs were investigated, which may provide a rational strategy for the design of novel ILs for extractive separation of structural analogues. The purification and recovery of vitamin D₃3 via continuous multistage extractions were simulated, indicating that IL-based liquid-liquid extraction might be superior to traditional organic solvents in practical production.

Extractant screening for the separation of dichloroacetic acid from monochloroacetic acid by extractive distillation

Monochloroacetic acid (MCA) is produced via the chlorination of acetic acid, in which a part is overchlorinated to the undesired dichloroacetic acid (DCA). The separation of DCA from MCA by distillation is highly energy intensive, because of the rather low relative volatility of ∼1.05–1.3, depending on the mixture composition. Extractive distillation is a promising alternative and often applied to separate close boiling mixtures. The benchmark solvent sulfolane is known to increase the relative volatility of the MCA/DCA mixture only slightly. By applying basic complexing agents, the large difference in the acid dissociation constant between MCA (pKa=2.87) and DCA (pKa=1.25) can be exploited to further enhance the relative volatility of the MCA/DCA mixture. The aim of this study was to select a proper complexing agent. Such a complexing agent should not only enhance the relative volatility more than obtained with sulfolane, but also be stable in the presence of MCA and DCA, and the complexation should be reversible. To study on the relative volatility and the reversibility of complexation, vapor–liquid equilibrium (VLE) and thermal/chemical stability experiments were performed. Many extractants were found that improve the relative volatility more than sulfolane, with relative volatilities up to 5.9. There is, however, a clear trade-off between the effect of the extractant on the relative volatility of the MCA/DCA mixture and the regeneration ability of the extractant. Extractants with a strong effect on the relative volatility of the MCA/DCA mixture appeared difficult to regenerate. Complexation agents from the classes of ethers, ketones, and phosphine oxides, and the benchmark extractant sulfolane were the only extractants that demonstrated to be thermally/chemically stable in the strongly acidic environment. With regard to the relative volatility, the regeneration ability, and the stability of the extractants, it was concluded that glymes, e.g. diethylene glycol dipentyl ether are the most promising extractants, improving the relative volatility of the MCA/DCA system up to 2.1–2.4 at a DCA/extractant molar ratio of 1.

Cyano-containing ionic liquids for the extraction of aromatic hydrocarbons from an aromatic/aliphatic mixture

Ionic liquids can replace conventional solvents in aromatic/aliphatic extractions, if they have higher aromatic distribution coefficients and higher or similar aromatic/aliphatic selectivities. Also physical properties, such as density and viscosity, must be taken into account if a solvent is applied in an industrial extraction process. Cyano-containing ionic liquids have a lower density than the benchmark solvent sulfolane and a higher viscosity. Sulfolane is from a hydrodynamic point of view a better solvent than ionic liquids for the aromatic/aliphatic extraction. The most suitable ionic liquids for the extraction of aromatic hydrocarbons from a mixture of aromatic and aliphatic hydrocarbons are [bmim]C(CN)3, [3-mebupy]N(CN)2, [3-mebupy]C(CN)3, [3-mebupy]B(CN)4 and [mebupyrr]B(CN)4. They have factors of 1.2–2.3 higher mass-based distribution coefficients than sulfolane and a similar or higher, up to a factor of 1.9 higher, aromatic/aliphatic selectivity than sulfolane. The IL [3-mebupy]N(CN)2 is a better extractant for the separation of toluene from a mixture of toluene/n-heptane in a pilot plant Rotating Disc Contactor (RDC) than sulfolane.

Binary and Ternary Vapor–Liquid Equilibrium Data of the System (Ethylbenzene + Styrene + 4-Methyl-N-butylpyridinium Tetrafluoroborate) at Vacuum Conditions and Liquid–Liquid Equilibrium Data of Their Binary Systems

Ethylbenzene and styrene are currently separated by ordinary fractional distillation, which is challenging due the low relative volatility of this mixture of 1.3 to 1.4. Extractive distillation is a promising alternative to save capital and operational expenditures. Recently, ionic liquids (ILs) have been reported as a promising option to replace commonly used organic solvents like sulfolane. The IL 4-methyl-N-butylpyridinium tetrafluoroborate ([4-mebupy][BF4]) is an IL with a strong effect on the relative volatility of the ethylbenzene/styrene mixture. In this work, binary VLE data in the range of (3 to 30) kPa, ternary VLE data at (5, 10, and 15) kPa, and binary LLE data at (313.2, 333.2, and 353.2) K have been determined for the system (ethylbenzene + styrene + [4-mebupy][BF4]). The ternary VLE experiments show that [4-mebupy][BF4] can enhance the relative volatility up to 2.7 to 2.8, and thereby [4-mebupy][BF4] has a stronger effect on the relative volatility than the benchmark solvent sulfolane, which can increase the relative volatility up to 2.3. Therefore, [4-mebupy][BF4] is a promising solvent for use in extractive distillation to separate ethylbenzene from styrene. The binary and ternary VLE data were correlated separately with the NRTL model and were regressed both together with the binary LLE data. The NRTL model could describe both data sets properly. The ternary VLE data could not be properly calculated by the binary NRTL parameters determined solely from the binary systems