Chemical fixation of carbon dioxide to dimethyl carbonate from propylene carbonate and methanol using ionic liquid catalysts

The synthesis of dimethyl carbonate (DMC) through the transesterification of propylene carbonate (PC) with methanol was investigated by using imidazolium salt ionic liquid catalysts. 1-alkyl-3-methyl imidazolium salts of different alkyl group (C₂, C₄, C₆, C₈) and anions (Cl⁻, Br⁻, BF₄⁻, PF₆⁻) were used for catalysts. The reaction was carried out in an autoclave at 140–180°C under carbon dioxide pressure of 1.48–5.61 MPa. The imidazolium salts of shorter alkyl group, and more nucleophilic counter anion exhibited higher catalytic activity. The conversion of PC increased as CO₂ pressure and reaction temperature increased. Kinetic studies were also performed to better understand the reaction mechanism. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Addition of carbon dioxide to allyl glycidyl ether using ionic liquids catalysts

The addition of carbon dioxide to allyl glycidyl ether (AGE) was investigated without using any solvent in the presence of ionic liquid as catalyst. Ionic liquids based on 1-ethyl-3-methylimidazolium (EMIm), 1-butyl-3-methylimidazolium (BMIm), and 1-hexyl-3-methylimidazolium (HMIm) with different anions such as Cl⁻, BF₄⁻, PF₆⁻ were used as catalysts. The reaction was performed in a 50 mL stainless steel autoclave. The conversion of allyl glycidyl ether was affected by the structure of imidazolium salt ionic liquids; the one with the cation of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. Reaction temperature and carbon dioxide pressure enhanced the addition of carbon dioxide to AGE.     

Cycloaddition of carbon dioxide to butyl glycidyl ether using imidazolium salt ionic liquid as a catalyst

The catalytic performance of imidazolium salt ionic liquids in the cycloaddition of carbon dioxide to butyl glycidyl ether (BGE) was investigated. The catalytic activity was tested with different imidazolium salt ionic liquids at 60–140 °C under 0.62–2.17 MPa of CO₂ pressure. The imidazolium salt ionic liquid with the cation of bulkier alkyl chain length and with more nucleophilic anion showed higher conversion of BGE. High carbon dioxide pressure and high reaction temperature up to 140 °C was favorable for the high reactivity of the catalyst. The presence of zinc bromide co-catalyst enhanced the reactivity of the imidazolium salt ionic liquid. Kinetic studies with a semi-batch reactor revealed that the reaction could be considered as first order with respect to the concentration of BGE, and the activation energy was estimated as 22.6 and 22.8 kJ/mol for 1-ethyl-3-methylimidazolium chloride (EMImCl) and 1-butyl-3-methylimidazolium chloride (BMImCl), respectively.     

Polymeric ionic liquid membranes as electrolytes for lithium battery applications

A new kind of polymeric ionic liquid (PIL) membrane based on guanidinium ionic liquid (IL) with ester and alkyl groups was synthesized. On addition of guanidinium IL, lithium salt, and nano silica in the PIL, a gel PIL electrolyte was prepared. The chemical structure of the PIL and the properties of gel electrolytes were characterized. The ionic conductivity of the gel electrolyte was 5.07 × 10⁻⁶ and 1.92 × 10⁻⁴ S cm⁻¹ at 30 and 80 °C, respectively. The gel electrolyte had a low glass transition temperature (T _g ) under −60 °C and a high decomposition temperature of 310 °C. When the gel polymer electrolyte was used in the Li/LiFePO₄ cell, the cell delivered 142 mAh g⁻¹ after 40 cycles at the current rates of 0.1 C and 80 °C.     

Study on Selective Dimerization of α-Methylstyrenes Promoted by Ionic Liquids

The catalytic systems composed of ionic liquids containing BF₄⁻ anion and HBF₄ showed high catalytic activity to produce 4-methyl-2,4-diphenyl-1-pentene (MDP-1) or 1,1,3-trimethyl-3-phenylindan (TPI) under different temperature conditions. Up to 90.8% selectivity to MDP-1 with a 98.7% conversion of α-methylstyrene was obtained at 60 °C in the presence of [HexMIm]BF₄–HBF₄, while exclusive TPI was yielded when the reaction temperature increased to 120 °C. Further studies showed that another ionic liquid, [BMIm]Cl · 2AlCl₃, could act as an excellent catalyst and solvent for the dimerization of α-methylstyrene to produce TPI. The dimerization of α-methylstyrene catalyzed by [HexMIm]BF₄–HBF₄ and [BMIm]Cl · 2AlCl₃ performed the same reaction mechanism and the proton was the active species.     

Synthesis of dimethyl carbonate from transesterification of ethylene carbonate with methanol using immobilized ionic liquid on commercial silica

Ionic liquid immobilized on commercial silica catalysts proved to be an effective heterogeneous catalyst for the synthesis of dimethyl carbonate (DMC) from transesterification of ethylene carbonate (EC) with methanol. The immobilized 1-n-alkyl imidazolium halide ionic liquid on commercial silica (RImX-CS) was characterized by EA, BET, FT-IR, ¹³C NMR and ²⁹Si NMR. It was found that RImX-CS with a longer alkyl chain length showed much better catalytic activity. RImX-CS with chloride (Cl⁻) as the counter anion showed the best catalytic activity. High temperature, high carbon dioxide pressure, and longer reaction time were favorable for the reactivity of BuImBr-CS. The catalyst can be reused for the reaction up to three consecutive runs without any considerable loss of its initial activity.     

Redox and transport behaviors of Cu(I) ions in TMHA-Tf<Subscript>2</Subscript>N ionic liquid solution

The redox and transport behavior of monovalent copper species in an ammonium imide-type ionic liquid, trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA-Tf₂N) were examined with a micro-disc electrode to clarify its applicability to, for example, electroplating. It was found that the diffusion coefficient of Cu(I) ions in TMHA-Tf₂N containing 12 mmol dm⁻³ Cu(I) ions was 1.2 × 10⁻⁶ cm² s⁻¹ and the redox potential of Cu(I)/Cu was in the potential range 0.1–0.2 V vs. I ⁻/I ₃⁻ at 50 °C. The diffusion coefficient was one order smaller than that of Cu(II) ions in aqueous solution due to the high viscosity of the ionic liquid. The diffusion coefficient of Cu(I) ion increased with rising temperature and was 1.0 × 10⁻⁵ cm² s⁻¹ at 112 °C, which was comparable to that of Cu(II) ions in aqueous CuSO₄ solutions at ambient temperature. This is accounted for by the drastic decrease in the viscosity of the ionic liquid solution with increasing temperature. The activation energy of diffusion was estimated to be 39 kJ mol⁻¹ in the ionic liquid solution.     

Ionic liquids based on 1-aza-bicyclo[2,2,2]octane (Quinuclidine) salts: synthesis and physicochemical properties

A series of new hydrophobic ionic liquids based on 1-alkyl-quinuclidinium cations, quoted as C _n Quin⁺ where n is the number of carbon atoms in the alkyl chain, and on the fluorinated anion bis(trifluoromethanesulfonyl)imide (TFSI⁻) were synthesized, characterized by NMR (¹H, ¹³C), and their elemental analysis determined. Among the five compounds synthesized, only one: C₆Quin(TFSI) is liquid at ambient temperature and the others with the exception of C₁Quin(TFSI), exhibit melting points below 100 °C and can be considered as ionic liquids. With the aim of using them as electrolytes in electrochemical devices, some of their physicochemical properties such as density, dynamic viscosity and conductivity were explored. The behaviour of C₆Quin(TFSI) at a graphite electrode was investigated in the presence of added LiTFSI, by means of cyclic voltammetry for possible use as electrolyte in Li-ion batteries. Results show that the large quinuclidinium cations intercalate in the graphite layers and do not permit the reversible insertion of lithium ions.     

Epoxidation of propylene by air over modified silver catalyst

Epoxidation of C₃H₆ to C₃H₆O by air was studied over a silver catalyst modified with alkali or alkaline earth chloride salts. The catalyst preparation factors and the operational conditions could affect obviously the catalytic epoxidation property of the silver catalyst. It was shown that, as a promoter of the silver catalyst, NaCl or BaCl₂ is more suitable than LiCl or NH₄Cl. The loading of NaCl should be controlled at about 3.8 wt%. Using a feed gas of 10% C₃H₆/air at a space velocity of 1.75×10⁴ h⁻¹, 18.6% C₃H₆ conversion and 33.4% selectivity to C₃H₆O were obtained at 350°C. Using a feed gas of 5% C₃H₆/air at a space velocity of 2.4×10⁴ h⁻¹, 54.0% C₃H₆ conversion and 26.3% selectivity to C₃H₆O were obtained at 390°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of temperature on the incorporation into phospholipid classes and metabolismvia desaturation and elongation of n−3 and n−6 polyunsaturated fatty acids in fish cells in culture

The incorporation of 18∶2n−6, 18∶3n−3, 20∶4n−6 and 20∶5n−3 was greater at 10°C than at 22°C in Atlantic salmon (AS), rainbow trout (RTG-2) and turbot (TF) cells. However, there were generally no significant differences between the amount of incorporation of all four polyunsaturated fatty acids (PUFA) into total lipid within a cell type at either 22°C or 10°C. The distributions of the PUFA between individual phospholipid classes at 22°C was essentially the same in AS and TF cells—with the C₁₈ PUFA the order of incorporation in these cells was phosphatidylcholine (PC) > phosphatidylethanolamine (PE) > phosphatidic acid/cardiolipin (PA/CL); with 20∶4n−6 the order was PE and phosphatidylinositol (PI)>PC; with 20∶5n−3, PE>PC. In RTG-2 cells at 22°C the distributions of the C₁₈ PUFA were similar to the other cell lines, but with 20∶4n−6 the order was PC>PI>PE, and with 20∶5n−3 it was PC>PE. At 10°C the incorporation of C₁₈ PUFA into PC increased and into PE and PA/CL decreased, in general, in all cell lines. Incorporation of 20∶5n−3 into PC and PE was increased and decreased at 10°C, respectively, in AS and TF cells, whereas in RTG-2 cells the changes at 10°C were opposite i.e., increased in PE and decreased in PC. With 20∶4n−6, incorporation into PC at 10°C was increased in all cell lines with decreased incorporation into PI in AS and RTG-2 cells and into PE in AS and TF cells, whereas incorporation of 20∶4n−6 into PE increased in RTG-2 cells. The metabolismvia desaturation and elongation of the n−3 PUFA was greater than that of the equivalent n−6 PUFA in all cell lines, irrespective of temperature. There was less conversion of the C₁₈ PUFA at 10°C than at 22°C in RTG-2 and TF cells, but the conversion of 18∶3n−3 by AS cells was increased at 10°C. Temperature had no effect on the conversion of the C₂₀ PUFA.     

Copolymerization of phenyl glycidyl ether with carbon dioxide catalyzed by ionic liquids

The copolymerization of phenyl glycidyl ether (PGE) and carbon dioxide was performed without any solvent in the presence of ionic liquid as catalyst. The reaction was carried out in a batch autoclave reactor. The carbonate content of polycarbonate was affected by the structure of imidazolium salt ionic liquid; the one with the cation of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. However, the yield of carbon dioxide addition decreased when hexyl or octyl containing ionic liquids were used in place of butyl group in 1-alkyl-3-methyl imidazolium salts. The carbonate content and turnover number (TON) of the polycarbonate increased as the reaction temperature increased from 40 to 80 ‡C. However, the carbonate content decreased with increasing reaction time.     

Synthesis of cyclic carbonate from vinyl cyclohexene oxide and CO2 using ionic liquids as catalysts

Synthesis of cyclic carbonate from 4-vinyl-1-cyclohexene-1,2-epoxide (VCHO) and carbon dioxide was investigated without using any solvent in the presence of ionic liquid as a catalyst. Ionic liquids based on 1-alkylmethylimidazolium salts of different alkyl groups (ethyl, butyl, hexyl, octyl) and different anions (Cl⁻, BF₄⁻, PF₆⁻) were used as catalysts. The conversion of VCHO was affected by the structure of the imidazolium salt ionic liquids; the ones with the cations of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. Reaction temperature, carbon dioxide pressure, and zinc halide cocatalyst enhanced the addition of CO₂ to VCHO. Semi-batch operation with continuous supply of carbon dioxide showed higher VCHO conversion than batch operation did.     

Synthesis of thermally stable polyamides with pendant 1,3,4-oxadiazole units via direct polycondensation in ionic liquids

The synthesis of high molecular weight polyamides by using 1-methyl-3-alkyl imidazolium bromides (alkyl = C₃–C₈) as reaction media has been reported. Polymers were prepared from the reaction of 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine, POBD, and aromatic/aliphatic dicarboxylic acids in ionic liquids in the presence of triphenyl phosphite as a condensing agent without requiring any extra components such as CaCl₂ or pyridine. The number average molecular weight of the polymers was measured by vapor pressure osmometry. The effects of various reaction parameters such as alkyl chain length of ionic liquids, reaction temperature, and reaction time on the molecular weight were investigated. No regular relationship between inherent viscosity or molecular weight with the alkyl chain length in the ionic liquid was observed; however, the highest molecular weight was observed in 1-butyl-3-methyl imidazolium bromide. The thermal properties of the prepared polymers were also studied with DSC and TGA methods. Removal of Co²⁺ from aqueous solutions was performed using polymer (7).     

Exploring the effect of alkyl end group on poly(L-lactide) oligo-esters. Synthesis and characterization

Poly(L-lactide) (PLLA) oligo-esters with α-hydroxyl-ω-alkyl (alkyl = −CH₂−[CH₂−CH₂]_m−CH₃, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10) end groups were synthesized by ring-opening polymerization of L-lactide (L-LA) catalyzed by tin(II) 2-ethylhexanoate Sn(Oct)₂ in the presence of aliphatic alcohols as initiators (HO−CH₂−[CH₂−CH₂]_m−CH₃, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10). High yields (~ 62 to 71%) and M _n(NMR) in the range of 2120–2450 Da (PLLA) were obtained. Effects of alkyl end groups on thermal properties of the oligo-esters were analyzed by DSC, TGA and SAXS. Glass transition temperature (T _g) gradually decreases with increase in the percent of−CH₂−[CH₂−CH₂]_m−CH₃ end group, as results alkyl end group provides most flexibility to PLLA. An important effect of alkyl end group on a double cold crystallization (T _c1 and T _c2) was observed, and is directly related with the segregation phase between alkyl end group and PLLA. TGA analysis revealed that PLLA oligo-esters are more thermally stable with docosyl (−C₂₂H₄₅) respect to the butyl (−C₄H₉) end group, probably is due to steric hindrance of the end group (docosyl respect to butyl) toward intermolecular and intramolecular transesterification. SAXS analysis showed that alkyl end group as docosyl restricted the growth of lamellae thickness (D) due to steric hindrance. Characterization of hydroxyl and alkyl end groups in the PLLA oligo-esters was determined by MALDI-TOF, GPC, FT-IR and ¹ H and ¹³ C NMR.     

Cation and anion sizes influence in the temperature dependence of the electrical conductivity in nine imidazolium based ionic liquids

In this paper we present experimental data on the temperature dependence of the electrical conductivity, σ, in nine different imidazolium based ionic liquids. We have measured four 1-(alkyl chain)-3-methyl imidazolium tetrafluoroborate (C_nMIM-BF₄) ionic liquids, with C_n representing ethyl, butyl, hexyl and octyl chains, to study the dependence of σ with the cation length. Moreover, to study the influence of the anion size in the electrical conductivity, we measured six different EMIM-X, with X being, from smaller to bigger sizes, Cl⁻, Br⁻, BF₄⁻, PF₆⁻, ethyl sulfate and tosylate. The measurements were performed at atmospheric pressure, and the studied temperature range covers the liquid phase of the analyzed compounds. We have fitted the electrical conductivity data of the nine ionic liquids using a Vogel-Tamman-Fulcher (VTF) equation with high precision. We observe from the measured data that the electrical conductivity decreases its value as the alkyl chain of the cation increases. In contrast, we do not observe that dependence with the anion size, where there seems to be an optimal size (that of BF₄⁻) for which σ reaches its maximum value, being lower for smaller or bigger anion sizes. Finally, if we plot the natural logarithm of σ versus the distance in temperature to the glass transition one for each IL, we observe that the resulting straight lines are ordered with the anion (or cation) sizes for all nine compounds measured, i.e., lower σ values for bigger sizes.     

Surface interaction of quaternary amines with hair

Surface analysis by X-ray photoelectron spectroscopy (XPS) has shown specific 1∶1 (ionic) interaction between cationic alkyl quaternary surfactant molecules and the anionic sulfonate groups present on the hair surface. The primary driving force for the adsorption of alkyl quaternary amine molecules to the surface of the hair from aqueous solution is the ionic interaction between quaternary groups and the surface SO₃ ⁻ on the hair. Cationic quaternary molecules incorporating ester and alcohol functionalities (ester quats) demonstrate a lower number of surface quaternary nitrogens per sulfonate group, indicating an altered surface interaction mechanism. For the ester quats, a combination of electrostatic interaction modes exists in addition to the ionic N⁺/SO₃ ⁻ interaction, specifically, H-bonding interactions of the −C−O, −C−OH, and −C(O)O− polar groups with SO₃ ⁻ and other polar groups on the hair. Surface coverage of the ester quat is not reduced despite the decrease in ionic interaction at the surface. Both types of molecules orient their alkyl tails toward the surface. Molecular dynamics modeling of the surfactant/hair surface interaction indicates higher adsorption energies due to increased dipolar interactions for ester quat molecules.     

Ionic liquids as catalytic additives for the acceleration of the photopolymerization of poly(ethylene glycol dimethacrylate)s

BACKGROUND: The fast development of practical applications of photopolymerizable compositions (PPCs) leads to a growing demand for the elaboration of novel monomers and simultaneously for the investigation of three‐dimensional polymerization mechanisms including the possible influence of initiator, additives, etc. The aim of the current study is to explore and clarify the role of ionic liquids (ILs) as environmentally friendly catalytic additives in the photopolymerization of poly(ethylene glycol dimethacrylate)s. RESULTS: The photopolymerization of triethylene glycol dimethacrylate (TEGDM) and poly(ethylene glycol‐400 dimethacrylate) (PEGDM) in the presence of various ILs both imidazolium‐based, i.e. [1‐methyl‐3‐alkylim]⁺ (CF₃SO₂)₂N^? (im = imidazolium; alkyl = C₂H₅, C₄H₉, C₁₄H₂₉), and phosphonium‐based, i.e. [P⁺ (C₆H₁₃)₃(C₁₄H₂₉)]X^? (X^? = PF₆^?, BF₄^?, (CF₃SO₂)₂N^?, Cl^?), as catalytic additives was investigated. The influence of the concentration of the ionic salts as well as the nature of the ILs upon the photopolymerization was studied in detail. It was found that imidazolium ILs accelerate TEGDM photopolymerization and suppress the polymerization of PEGDM. In contrast, polymerization of PEGDM with extra small amounts of phosphonium ionic solvents proceeded at a high rate and offered access to new polymers and the utilization of low‐reactivity monomers in PPCs. CONCLUSION: The most striking advantage is that the use of certain ILs permits the control of polymerization rate to achieve maximum oligomer conversion. Copyright © 2007 Society of Chemical Industry     

Synthesis of alcohols from CO and H<Subscript>2</Subscript> on iron catalysts containing carbon fiber

It was found that alcohols can be synthesized from CO and H₂ at 3 MPa and 280–300°C in the presence of Fe catalysts containing an activated fibrous carbon material (AFCM) as a support. It was established that 20% Fe/AFCM catalysts possess an extremely high specific activity in the conversion of carbon monoxide (∼1 × 10⁻⁴ mol CO (mol Fe)⁻¹ s⁻¹), which is higher than the activity of traditional bulk iron catalysts by almost an order of magnitude. The values of CO conversion and selectivity for alcohols obtained for these catalysts are close to the parameters of industrial processes (Synol process, Oxyl process, and synthesis according to Bashkirov); however, they are obtained under milder conditions in a single run rather than with the use of a recycle. The Fe/AFCM catalysts make it possible to obtain monohydric alcohols in yields to ∼50 g/m³ (to a 50% concentration in synthesis water) upon the almost complete conversion of CO. In this case, the fraction of C₂-C₄ alcohols was as high as 55–60%.     

Sorption kinetics of carbon dioxide onto rubidium carbonate

Rubidium carbonate was used as an adsorbent to capture carbon dioxide from gaseous stream of carbon dioxide, nitrogen, and moisture in a fixed-bed to obtain the breakthrough data of CO₂. Experiments were carried out at flow rates of carbon dioxide and nitrogen (5×10⁻⁶–35×10⁻⁶ m³/min), moisture (0.5×10⁻⁶–3.0×10⁻⁶ m³/h), amount of adsorbent (0.5×10⁻³–1.8×10⁻³ kg), mole fraction of carbon dioxide (0.03–0.22), and different sorption temperatures (323–353 K) at atmospheric pressure. The deactivation model in the non-catalytic heterogeneous reaction systems was used to analyze the sorption kinetics among carbon dioxide, carbonate, and moisture, employing the experimental breakthrough data that fit the deactivation model better than the adsorption isotherm models in the literature.     

Synthesis of mycolic acid biosurfactants and their physical and surface-active properties

Five mycolic acids [2-alkyl-3-hydroxy FA: R₁C^*(OH)C^*HR₂COOH] were synthesized using acyl chlorides with alkyl chains of different lengths (total carbon numbers of mycolic acids, 12, 16, 20, 24, 36). The relationship between the chemical structures of the mycolic acids and their surface-active properties was determined. The acids were synthesized in three steps: (i) dimerization of acyl chloride into alkyl ketene dimer, (ii) selective reduction of C=C to C-C by hydrogenation, and (iii) β-lactone ring cleavage under alkaline conditions. The yields of C₁₂-, C₁₆-, C₂₀-, C₂₄-, and C₃₆-mycolic acid were 72, 73, 73, 73, and 73%, respectively. The critical micelle concentrations (CMC) of C₁₂-, C₁₆-, and C₂₀-mycolic acid were 2.2×10⁻⁴, 1.36×10⁻⁴, and 7.4×10⁻⁵ M, respectively. As the carbon number increased, the surface tension at the CMC value was also lower; the values for C₁₂-, C₁₆- and C₂₀-mycolic acid were 46.54, 43.59, and 41.57 dyn/cm, respectively. The emulsifying activities of mycolic acids were determined for n-tetradecane, n-hexadecane, cyclohexane, and diesel oil. The results showed that C₁₂-mycolic acid was the best emulsifier for diesel oil, C₁₆-mycolic acid was the best emulsifier for n-tetradecane and n-hexadecane, and C₂₀-mycolic acid was the best emulsifier for cyclohexane. This study showed that mycolic acids having, surface-active properties can be chemically synthesized for potential applications in the detergent/cleaning material industries, for example, in oil spill cleanup, oil recovery, textiles, pharmaceuticals, and cosmetics.