Tetraethylammonium Acetate Research Articles

Separation of methyl ethyl ketone - methanol azeotrope by ionic liquids: Thermodynamic and molecular mechanism

In this work, three ionic liquids (ILs) based on acetate, namely tetraethylammonium acetate ([N2222][Ac]), 1-hexyl-2,3-dimethylimidazolium acetate ([HMMIM][Ac]), and tributylmethylammonium acetate ([N4441][Ac]) were selected to separate the methyl ethyl ketone - methanol azeotrope. The vapor–liquid equilibrium (VLE) data of the binary system (methyl ethyl ketone + methanol) and the ternary systems (methyl ethyl ketone + methanol + IL) were measured at 101.3 kPa. It was found that all the experimental data were thermodynamically consistent and the three ionic liquids could effectively eliminate the azeotropic phenomenon at a specific concentration. The separation ability of the three ionic liquids is [N2222][Ac] > [HMMIM][Ac] > [N4441][Ac]. The NRTL model was used to correlate the VLE data and was found to have an excellent quality of fit. Moreover, the quantum chemical calculations, COSMO-RS model, and FT-IR analysis were used synergistically to provide microscopic insights into the separation mechanism of ionic liquids.

Synthesis and Characterization of Cyclotri- and Tetrasiloxanes with Pyrenyl Groups.

Cyclosiloxanes directly bearing polyaromatic groups on silicon atoms have scarcely been reported. Herein, hexa(1-pyrenyl)cyclotrisiloxane (2) and octa(1-pyrenyl)cyclotetrasiloxane (3) were successfully prepared from di(1-pyrenyl)silanediol (1) in the presence of a weak base such as tetraethylammonium acetate and triethylamine in MeCN. The structure of the cyclosiloxanes bearing multiple pyrenyl groups in the solid and solution states was evaluated by NMR, X-ray crystallography, and density functional theory (DFT) calculations. All pyrenyl groups of 2 were oriented outward, and no π-π stacking of adjacent pyrenyl groups was observed. However, all pairs of adjacent pyrenyl groups at 1- and 3-positions in 3 are oriented in the same direction and were π-π stacked with respect to each other. The UV-vis spectra of 2 and 3 in organic solvents showed a slight broadening of the peaks, as observed for typical pyrene derivatives. Interestingly, the fluorescence spectra of 2 showed small monomer and strong excimer emissions; however, those of 3 showed only a strong excimer emission in all solvents. Partially pyrenylated cyclotri- and tetrasiloxanes (compounds 4 and 5) showed solvent-dependent monomer and excimer spectra as observed for di(1-pyrenyl)silane derivatives, implying that the excimer emissions of 2 and 3 arise from mainly geminal and vicinal pyrenyl groups, respectively.

Isobaric vapor-liquid equilibrium for 2-butanone + ethanol + acetate-based ionic liquids at 101.3 kPa

Three acetate-based ionic liquids (ILs) (tetraethylammonium acetate, [N2,2,2,2][AC]; 1‑butyl‑2,3-dimethylimidazolium acetate, [BMMIM][AC]; or tributyl-methylammonium acetate, [N4,4,4,1][AC]) were used to separate the 2-butanone-ethanol azeotropic mixture as entrainer. The separation abilities of the three ILs were compared by measuring isobaric vapor-liquid equilibrium (VLE) data of the 2-butanone + ethanol + IL ternary systems at 101.3 kPa. The VLE data were well correlated through the use of the nonrandom two-liquid (NRTL) model. The azeotrope of 2-butanone + ethanol binary system is entirely eliminated when the concentration of IL achieves a certain value. The minimum mole fractions of the three ILs to completely eliminate azeotropic phenomena are 0.0146, 0.0166 and 0.0240, respectively. The breaking azeotropic capacities of the three ILs are better than that previously reported in the literatures. According to the average relative volatility, after the azeotropic point is thoroughly eliminated, the order of the separation capability of the three ILs is as below: [N2,2,2,2][AC] > [BMMIM][AC] > [N4,4,4,1][AC]. The σ-profiles were used to further explore the separation mechanism.

Tetraethylammonium Acetate and Tetraethylammonium Bromide-Based Deep Eutectic Solvents as Thermodynamic CO2 Gas Hydrate Inhibitors

The thermodynamic gas hydrate suppression behavior of four Deep Eutectic Solvents (DESs) was evaluated in this paper. The mixtures of Hydrogen Bond Acceptors (HBA), Tetraethylammonium Acetate (TEAAC), and Tetraethylammonium Bromide (TEAB) with Hydrogen Bond Donors (HBD), Mono-Ethylene Glycol (MEG), and Glycerol were used to make the DES. The DESs were made at a 1:7 molar ratio for the combinations of TEAAC:MEG, TEAAC:Glycerol, TEAB:MEG, and TEAB:Glycerol. The Hydrate Liquid-Vapor Equilibrium (HLVE) data for CO2 were evaluated through the T-cycle method at different temperature (273.15–283.15 K) and pressure (2–4 MPa) conditions in the presence and absence of 5 wt % aqueous DES solutions. The inhibition effects showed by the DESs, including average suppression temperature (ΔŦ) and gas hydrate dissociation enthalpies (ΔHdiss), were also calculated. The average suppression temperature values of the DESs ranged between 0.4 and 2.4, with the highest inhibition to lowest inhibition order being TEAB:Glycerol > TEAB:MEG > TEAAC:Glycerol > TEAAC:MEG. A comparison of the DES with conventional Thermodynamic Hydrate Inhibitors (THIs) showed that studied Deep Eutectic Solvents had better gas hydrate inhibition. The results proved that DES has the potential to be one of the promising alternatives in gas hydrate inhibition.

Dual Catalyst System for Asymmetric Alternating Copolymerization of Carbon Dioxide and Cyclohexene Oxide with Chiral Aluminum Complexes: Lewis Base as Catalyst Activator and Lewis Acid as Monomer Activator

Optically active aluminum complexes such as Schiff base, binuclear β-ketoiminate, and bisprolinol complexes were found to promote asymmetric alternating copolymerizations of carbon dioxide and cyclohexene oxide. The aluminum Schiff base complexes–tetraethylammonium acetate afforded isotactic poly(cyclohexene carbonate)s with low enantioselectivities. Lewis bases having two coordinating sites were utilized to enhance activity and selectivity based on the binuclear structure of the aluminum β-ketoiminate clarified by X-ray crystallography. [2gAlMe]2–bulky bisimidazole produced the alternating copolymer with high enantioselectivity (62% ee). The polymerization is considered to preferentially proceed at more crowded, enantioselective site owing to coordination of bulky Lewis bases to aluminums in less enantioselective sites. 32AlMe–2-picoline also exhibited a high enantioselectivity (67% ee). Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) was applied to perform faster and more enantioselective copolymerizations at low temperature (82% ee). The asymmetric copolymerizations were found to be significantly dependent on size of epoxide, temperature, and kind/amount of activators.

Palaeoenvironment assessment of Pliocene Lom lignite (Bulgaria) from bitumen analysis and preparative off line thermochemolysis

The Dacian coal bearing province is located in NW Bulgaria. Coal formation is thought to be connected with desiccation of the Dacian Basin during a prolonged regression in the Late Pontian and Pliocene (Dacian–Romanian age). A Lom lignite sample was characterized via micropetrography, bulk chemical analysis, spectral methods and thermochemolysis. The pollen record was poor, suggesting coal formation under oxygen-rich conditions during peatification. Straight chain alkanes, alkan-2-ones, alkanols, des-A-triterpenoids, aromatized triterpenoids, aromatized hopane, hopene/hopanes and triterpenoids with a strong dominance of oleanane-derived structures were present in the extracted bitumen. The residue after extraction was subjected to preparative off line tetramethylammonium hydroxide (TMAH) thermochemolysis. The aliphatic products released were C 22–C 27 fatty acid (FA) methyl esters, i.e. α-methoxymethyl esters, C 22–C 28 even numbered α,ω-diacids dimethyl esters with a smooth distribution and traces of i- and ai-C 15 acid methyl esters. Trapped and bound FAs were distinguished using tetraethylammonium acetate (TEAAc) treatment. The main thermochemolysis products were phenols structurally related to lignin. Vanillyl and syringyl units were produced in similar amounts, indicating nonwoody angiosperm vegetation as the main plant input to the palaeo-swamp, probably originating from marsh or grassland sources. The bitumen provided unequivocal information for an angiosperm contribution to the mire, while the results of the TMAH pyrolysis revealed a concomitant angiosperm and gymnosperm input. The biomarker assemblage makes the Lom lignite unique in Bulgaria, all the other Bulgarian Neogene lignites being dominated by coniferous vegetation, with only traces of angiosperm contributions.

Abstract 1574: Inhibition Of Extracellular Ca 2+ Influx And Rho Kinase Mediate Hypoxic Dilation Of Human Mammary Artery

Objective : Systemic artery dilates in response to decrease in Po 2 , to maintain blood supply to stressed organ. However, the mechanism of hypoxic dilation is still unknown and the effect of hypoxia on human systemic arteries is infrequently studied. Since the internal mammary artery (IMA), a routinely used bypass conduit, is often exposed to low Po 2 that evokes vasospasm and leads to hypo-perfusion of myocardium in peri- and post-operative conditions, we initiated this study to elucidate the mechanism of hypoxic dilation in IMA. Methods & Results : The distal IMA was collected during a CABG surgery in a blinded-fashion and 2–3 mm rings were used in the isometric tone study. The IMA rings pre-contracted with either KCl (30 mM; n=7), a depolarizing agent, or phenylephrine (PE: 10 μM; n=7), a α-adrenergic agonist, relaxed to 34 ± 12% and 10±7%, respectively, of the steady-state pre-hypoxic contraction, in a time-dependent manner by decreasing Po 2 from 140 to 30 torr. The initiation of hypoxic dilation was mediated by opening of K + channels, because IMA pre-contracted with PE relaxed (P=0.027) to 74±12% of the steady-state pre-hypoxic contraction @ 3 minutes by hypoxia and tetraethylammonium acetate (TEA; 10 mM), a K + channel blocker, suppressed (P=0.059) relaxation (97.4±1.6% @ 3 minutes). More interestingly pretreatment of IMA with Y-27362 (10 μM), a Rho kinase inhibitor, shifted Ca 2+ sensitivity to the right, since [Ca 2+ ] o required to induce 50% contraction of IMA by KCl (30 mM) was shifted from 0.3±0.1 mM (control) to 1.1±0.1 mM (Y-27362), and decreased (P=0.043) hypoxic dilation (Y-27362+KCl: 74±14%; n=5 versus KCl: 34±12%; n=7; @ 3 minutes). Hypoxia also shifted Ca 2+ sensitivity and suppressed (P<0.005) steady-state contraction (Normoxia: 4.3±0.1g versus Hypoxia: 1.2±0.6g) evoked by 1.5 mM [Ca 2+ ] o . Conclusion : Our results, therefore, demonstrate that inhibition of extracellular Ca 2+ influx and Rho kinase plays a major role in hypoxic dilation of human artery and we propose that response of IMA conduits to hypoxia could be compromised in hypertension and diabetes in which the Ca 2+ handling and Rho kinase is modulated, leading to hypo-perfusion of myocardium in hypertensive/diabetic patients undergoing CABG surgery. (Supported by AHA Grant #0435070N)

Simultaneous determination of ampicillin, cefoperazone, and sulbactam in pharmaceutical formulations by HPLC with β‐cyclodextrin stationary phase

An accurate and reproducible method for the simultaneous determination of ampicillin (AMP), sulbactam (SUL), and cefoperazone (CFP) in pharmaceutical formulations by using HPLC with beta-CD stationary phase was developed. It involved the use of the added tetraethylammonium acetate (TEAA) reagent, pH, and methanol as the significant parameters to find the optimum separation condition. A high resolution and selectivity of analytes was obtained by running the mobile phase in methanol-5 mM TEAA buffer = 35:65 (v/v, pH 4.5) at 280 nm. The mean recoveries ranged from 96.6 to 103.3% for AMP in the synthetic mixture, 97.6 to 103.0% for SUL, and 97.0 to 104.0% for CFP. The low LOD (<1.8 microg/mL) and low CV (<0.9%) assured that this method was sensitive and reproducible. The assay of analytes in commercial products exhibited that it was convenient and reproducible for routine analyses of these components in sterilized H(2)O, saline, or 5% dextrose injection solutions.

Alternating copolymerization of carbon dioxide and epoxide catalyzed by an aluminum Schiff base–ammonium salt system

AbstractThe alternating copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO2 and CHO with the (Salophen)AlMe (1a)–tetraethylammonium acetate (Et4NOAc) system. When a mixture of the 1a–Et4NOAc system and CHO was pressurized by CO2 (50 atm) at 80 °C in CH2Cl2, the copolymerization of CO2 and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO2 and CHO with an almost perfect alternating structure. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis indicated that an unfavorable reaction between Et4NOAc and CH2Cl2 and a possible chain‐transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172–4186, 2005

Lipid constituents of peat humic acids and humin. Distinction from directly extractable bitumen components using TMAH and TEAAc thermochemolysis

Humic acids and humin from an acidic peat were investigated using solid state 13C NMR and pyrolysis with tetramethylammonium hydroxide (TMAH) and tetraethylammonium acetate (TEAAc). The degradation products were compared with the solvent extractable lipids. The latter appeared to originate mostly from plant material, whereas the products derived from the humic fractions showed a more complex structure, partly inherited from natural insoluble material. The major products of TMAH thermochemolysis were aromatic compounds derived from lignin moieties, hydrocarbons and fatty acid methyl esters (FAMEs) partly incorporated via ester or ether bonds. Aliphatic hydrocarbons were present as n-alkene/ n-alkane doublets with a Gaussian distribution in the C 17–C 35 range. These unsaturated and saturated hydrocarbons arose from resistant biopolymers. Bifunctional aliphatic compounds were also incorporated into the humic structure, contributing to alkyl bridges. Thermochemolysis of humin produced more aliphatic structures than did humic acids. The application of TEAAc thermochemolysis allowed identification of a wide range of products initially retained in the humic macromolecules via non-covalent bonds, thereby indicating that weak bonds such as hydrogen bonds play a key role in the structure of humic substances. The association of thermochemolysis using TMAH and TEAAc thus allows covalently-bound fatty acids, trapped fatty acids and trapped fatty acid methyl esters present in the structure of humic acids or humin to be distinguished.

High-performance liquid chromatography purification of 26-bp serial analysis of gene expression ditags results in higher yields, longer concatemers, and substantial time savings

In contrast to DNA chips, serial analysis of gene expression (SAGE) is not dependent on genes having been previously identified for their monitoring. Although useful, the method can be technically challenging, and particularly the last steps including concatenation and cloning may result in less than optimal results. We propose that many of the encountered problems can be attributed to the purification of the 26-bp ditags by polyacrylamide gel electrophoresis. Low yields, gel contaminants, potential exposure to degrading enzymes during handling and lengthy separation all disfavor the method. We introduce purification of 26-bp ditags by reverse-phase high-performance liquid chromatography (HPLC) using polystyrene/divinylbenzene columns and tetraethylammonium acetate buffer with acetonitrile as mobile phase. The method is fast and gives excellent results. Ditags purified by HPLC readily ligate to high-molecular-weight concatemers leading to their efficient cloning. The method should substantially facilitate the construction of SAGE libraries.

SEPARATION AND DETERMINATION OF β-LACTAMASE INHIBITORS IN HUMAN SERUM BY HPLC WITH A β-CYCLODEXTRIN STATIONARY PHASE

ABSTRACT A high performance liquid chromatography (HPLC) method has been developed for the separation and quantitation of clavulanic acid (CA), sulbactam (SUL), and tazobactam (TAZ) in human sera. The optimum mobile phase used in conjunction with a β-cyclodextrin (β-CyD) column contained methanol-5 mM tetraethylammonium acetate (TEAA) (35 : 65, v/v, pH 4.5) and 1.0 mL/min flow rate for chromatographic separation. The mean recoveries of CA, SUL, and TAZ range from 84.4 to 87.8%, 88.4 to 90.6%, and 89.0 to 90.8% respectively, from human serum samples spiked with the inhibitors, are routinely obtained. The lower limit of quantitation ( < 0.156 µg/mL) and the low coefficient of variation ( < 3.92%) assure that this method is sensitive and reproducible.

Hydrogen sulfide separation from gas streams using salt hydrate chemical absorbents and immobilized liquid membranes

The salt hydrate tetramethylammonium fluoride tetrahydrate, [(CH3)4N]F·4H2O, in the liquid state reversibly absorbs large quantities of hydrogen sulfide, for example 0.30 mol H2S per mole of salt at 50°C and 100 kPa. Gas absorption likely occurs by deprotonation of H2S to form bisulfide, HS−, and bifluoride, HF2 −. The equilibrium constant for the reaction of H2S with [(CH3)4N]F·4H2O is 1.4 × 10− 2 kPa− 1 at 50°C as determined from absorption/desorption data. The heat of H2S absorption was surprisingly low, −0.78 kcal mol− 1. A second salt hydrate, tetraethylammonium acetate tetrahydrate, [(C2H5)4N]CH3CO2·4H2O, also reversibly absorbs H2S but with a lower affinity. However, at higher pressures, its H2S capacity increases more than does that of [(CH3)4N]F·4H2O making it more suitable for use as a pressure swing absorbent. Absorption/desorption data are consistent with reaction of one mole of [(C2H5)4N]CH3CO2·4H2O for each mole of H2S and an equilibrium constant of 6.4 × 10− 4 kPa− 1 mol H2S per mole of salt. Membranes consisting of liquid [(CH3)4N]F·4H2O immobilized in a microporous support exhibit selective permeation of H2S from CH4 and CO2. Permeabilities of H2S increased with decreasing feed pressure, consistent with facilitated transport of H2S. The H2S/CH4 selectivities ranged from 140 to 34 and decreased with increasing feed pressure while H2S/CO2 selectivities were 8–6. The presence of H2S in the feed tends to suppress permeation of CO2, implying that both gases compete for the same carrier species.

Free and esterified aliphatic carboxylic acids in humin and humic acids from a peat sample as revealed by pyrolysis with tetramethylammonium hydroxide or tetraethylammonium acetate

The combination of TMAH thermochemolysis and TEAAc treatment makes it possible to discriminate between the different forms of mono- and dicarboxylic acids present in the structure of humin and humic acids, that is, “free” uncombined acids, methyl or ethyl esters present as tightly trapped molecules within the matrix, or acids chemically linked to the matrix by ester groups. The results confirm that ester groups are involved in the structure of humin and humic acids. The cross-linking of moieties originating from microbial metabolism or inherited from higher plants is partly ensured by these chemical groups. On the other hand, significant amounts of fatty monocarboxylic acids and linear dicarboxylic acids are present as free acids in the humin of the studied sample. Humin contains also fatty acid methyl esters. Free, uncombined α,ω-dicarboxylic acids were only found in humin.

ROOM TEMPERATURE MOLTEN CARBOXYLATE SALT HYDRATES

The mono- and dihydrates of tetraethylammonium acetate, [(C2H5)4N]CH3CO2, were found to be liquids at room temperature even though the corresponding tetrahydrate is a solid. The lower hydrates were synthesized by prolonged drying of the tetrahydrate. The monohydrate melts at 18°C. The 13C NMR and 1H NMR spectra of the monohydrate were consistent with the proposed structure. The monohydrate was stable with respect to decomposition for over one year under N2 at ambient temperature. Both hydrates exhibited large and reversible absorption of CO2 at 50°C. Spectroscopic data were consistent with absorption of CO2 as bicarbonate. The related tetraethylammonium propionate salts containing 2 and 0.9 mol H2O/mol salt were also found to be liquids at room temperature.

Simultaneous determination of amoxycillin and clavulanic acid in pharmaceutical products by HPLC with β-cyclodextrin stationary phase

A simple, rapid and accurate method for simultaneous determination of amoxycillin and clavulanic acid using HPLC with β-cyclodextrin stationary phase was developed. It involves the use of tetraethylammonium acetate (TEAA) as an additive reagent, methanol-buffer solution (pH 4.5) (35:65; v/v) as the mobile phase, detection at 225 nm and chromatogram within 12 min. Linearity and precision of the internal standard method have been obtained. Recoveries ranged from 99.25 to 105.63% for amoxycillin in the synthetic mixture. For clavulanic acid it was from 99.50 to 101.64%. This method is convenient and reproducible for analyses of these two components in different dosage forms.

Manipulation of the delayed rectifier Kv1.5 potassium channel in glial cells by antisense oligodeoxynucleotides.

Glial cells have been shown to express several biophysically and pharmacology distinct potassium channel types. However, the molecular identity of most glial K+ channels is unknown. We have developed an antibody specific for the Shaker type potassium channel Kv1.5 protein, and demonstrate by immunohistochemistry the presence of this channel in glial cells of adult rat hippocampal and cerebellar slices, as well as in cultured spinal cord astrocytes. Immunoreactivity was particularly intense in the endfoot processes of astrocytes surrounding the microvasculature of the hippocampus. The specific contribution of this channel protein to the delayed rectifying K+ current of spinal cord astrocytes was determined by incubating these cells with antisense oligodeoxynucleotides complementary to the mRNA coding for Kv1.5 protein. Such treatment reduced delayed rectifier current density and shifted the potassium current steadystate inactivation, without altering current activation, cell capacitance, or cell resting potential. The tetraethylammonium acetate (TEA) sensitivity of astrocytic delayed rectifier current was enhanced following antisense oligodeoxynucleotide treatment, suggesting that Kv1.5 channel protein may provide a significant component of the TEA-insensitive current in this preparation. Our results suggest that Kv1.5 is widely expressed in glial cells of brain and spinal cord and that delayed rectifying K+ currents in astrocytes are largely mediated by Kv1.5 channel protein.

The Effects on Separation of Cephalosporins by HPLC with β-Cyclodextrin Bonded Stationary Phase

Abstract A β-cyclodextrin bonded stationary phase is used for the liquid chromatographic separation of cephalosporins. A complete separation of nine cephalosporins with methanol and tetraethylammonium acetate (TEAA) buffer solution has been demonstrated. It is also found that a 100% of TEAA buffer solution is suitable for the separation of cephalosporins containing a hydrophilic α-amino moiety. The effects of pH, TEAA concentration, organic modifier concentration of mobile phase, and the column temperature on the retention are examined and discussed.

Outward currents in heart motor neurons of the medicinal leech.

1. Outward currents were studied in isolation in heart motor neurons in the medicinal leech, using the single-electrode voltage-clamp technique. The currents were divided into four distinct types on the basis of their time and voltage characteristics and sensitivity to external Ca2+ concentration. 2. The four types were a fast transient current, IKA; a slow transient current. IK1; a noninactivating current, IK2, all measured in a bathing solution in which Co2+ was substituted for Ca2+; and a calcium-sensitive current. IK1Cal which was revealed in a bathing solution containing normal levels of Ca2+. 3. The outward currents in heart motor neurons studied in different ganglia possessed differences of quality. For example, heart motor neurons from ganglia 3 or 4 had significantly less IK2 and IK1 than neurons recorded from more posterior ganglia. Heart motor neurons from ganglion 3 often had little or no IK1. Soma input resistance, electrotonic length, and soma capacitance measured in heart motor neurons from both anterior and posterior ganglia exhibited no significant differences. 4. IKA started to activate near -45 mV with half-maximal activation at about -20 mV and was fully inactivated by 0 mV: IK1 started to activate near -45 mV with half-maximal activation at about -10 mV and was not fully inactivated by 0 mV; IK2 started to activate near -50 mV; IK1Cal started to activate near -35 mV. The time constant of removal of inactivation for IKA was 25 ms, measured at -80 mV, and that for IK1 was 380 ms, measured at -40 mV. 5. Tetraethylammonium acetate (TEA) allowed to diffuse from the inside of the recording microelectrode effectively blocked IKA, IK1, and IK2. Bath-applied TEA (25 mM) acted similarly but was less effective, particularly at blocking Ik2. Bath-applied 4-aminopyridine effectively blocked the transient currents IKA and IK1. A reversal potential of -65 mV was found for the outward currents, corresponding to a mix of IK1 and IK2.

New facilitated transport membranes for the separation of carbon dioxide from hydrogen and methane

New facilitated transport membranes which selectively permeate carbon dioxide from hydrogen and methane have been prepared and examined under a variety of conditions. Membranes consist of melts of the salt hydrates tetramethylammonium fluoride tetrahydrate, [(CH 3) 4N]F·4H 2O, or tetraethylammonium acetate tetrahydrate, [(C 2H 5) 4N]CH 3CO 2·4H 2O, immobilized in films of Celgard 3401®. Operating at 50°C, both membranes exhibited CO 2 permeabilities which increased with decreasing feed partial pressure of CO 2, characteristic of a facilitated transport membrane. Selectivities of CO 2 H 2 and of CO 2 CH 4 increased with decreasing feed pressure since H 2 and CH 4 permeances were independent of feed pressure. Selectivities of CO 2 H 2 were disappointingly low due to permeation of H 2 through the dense phase of Celgard®. With some difficulty, the microporous support was eliminated by construction of membranes consisting of liquid [(CH 3) 4N]F·4H 2O on the surface of a film of poly (trimethylsilylpropyne). Selectivities of CO 2 H 2 as high as 360 were then observed at low feed partial pressures of CO 2. Modeling of membrane properties is consistent with permeation of CO 2 by a facilitated transport mechanism with reasonable derived diffusivities for the chemically bound CO 2 carrier species.