Reverse atom transfer radical polymerization of methyl methacrylate in imidazolium ionic liquids

Reverse atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) employing 2,2-azobisisobutyronitrile (AIBN)/CuCl₂/bipyridine(bipy) as the initiating system was approached at 80 °C in two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) and 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C₁₂mim][BF₄]), respectively. The polymerization in [C₁₂mim][BF₄] proceeded in a well-controlled manner as evidenced by kinetic studies, end group analysis, chain extension, and block copolymerization results, but not in [C₄mim][BF₄] presumably due to poor solubility of PMMA in it. The kinetic study of reverse ATRP of MMA in recycled [C₁₂mim][BF₄] suggested that this ionic liquid could be re-used as reaction solvent after simple purification, without affecting the living nature of polymerization.     

ARGET ATRP of acrylonitrile with ionic liquid as reaction medium and FeBr3/isophthalic acid as catalyst system

Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile with FeBr₃ and isophthalic acid (IA) as catalyst and ligand, ascorbic acid (VC) as reducing agent, and ethyl 2‐bromoisobutyrate as initiator was approached for the first time in the presence of air in 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate ([C₁₂mim][BF₄]), 1‐octyl‐3‐methylimidazolium tetrafluoroborate ([C₈mim][BF₄]), and 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C₄mim][BF₄]). The rate of polymerization in [C₁₂mim][BF₄] was considerably faster than in [C₈mim][BF₄] and [C₄mim][BF₄]. With an increase of VC concentration, both the monomer conversion and the molecular weight distribution showed a trend of increase. Polyacrylonitrile (PAN) with higher molecular weight at 166,250 and broader distribution at 1.34 was successfully prepared with PAN as macroinitiator via ARGET ATRP in [C₁₂mim][BF₄] in the presence of air. The resultant polyacrylonitrile fibers were obtained with the fineness at 1.15 dtex and the tenacity at 6.24 cN dtex^?1. Additionally, it was shown that [C₁₂mim][BF₄] could be recycled and reused after simple purification and had no effect on the living nature of polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Recycling Chiral Imidazolidin‐4‐one Catalyst for Asymmetric Diels–Alder Reactions: Screening of Various Ionic Liquids

Various imidazolium ionic liquids such as [Bmim]PF₆, [Bmim]SbF₆, [Bmim]OTf and [Bmim]BF₄ were screened for recycling an organic catalyst [(5S)‐5‐benzyl‐2,2,3‐trimethylimidazolidin‐4‐one ( 1 )] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF₆ or [Bmim]SbF₆. However, reactions in [Bmim]OTf or [Bmim]BF₄ gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

Enrichment of Aromatic Compounds Using Ionic Liquid and Ionic Liquid-Based Aqueous Biphasic Systems

Both hydrophibic [C₈mim][PF₆] and [C₄mim]Cl/(K₂CO₃, K₂HPO₄ or K₃PO₄) aqueous biphasic system (ABS) were employed for the enrichment of aromatic compounds including nitrobenzene, 4-nitrophenol, phenol and aniline from aqueous solutions. In [C₈mim][PF₆] enrichment system, the distribution ratio (D) of nitrobenzene and aniline increase with the increasing of pH values of aqueous phase from 2 to 8, but there is no obvious change for 4-nitrophenol and phenol. And the D values of the aromatic compounds decrease with the phase ratio change from 1/5 to 1/30 (IL phase volume/aqueous phase volume). In [C₄mim]Cl/(K₂CO₃, K₂HPO₄ or K₃PO₄), the distribution ratio increase with the increasing of the salts concentrations. The distribution ratio order in [C₈mim][PF₆] and [C₄mim]Cl/kosmotropic salt ABS is nitrobenzene > phenol > aniline > 4-nitrophenol. It is expected that these results are promising for the removal of the aromatic compounds from water, especially for sample enrichment in analytical science.     

Improved activity and stability of pseudomonas capaci lipase in a novel biocompatible ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate

BACKGROUND: Enzymes may exhibit enhanced activity, stability and selectivity in ionic liquids, depending on the properties of the liquid. The physical–chemical properties of ionic liquids, however, may be modified by altering the anion or cation in the ionic liquid. This feature is a key factor for realizing successful reactions. In this work, a new ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [i‐C₄mim][PF₆]), was synthesized and investigated as a novel medium for the transesterification reaction of 2‐phenylethanol with vinyl acetate catalyzed by pseudomonas capaci lipase. As contrasts, the reaction was also carried out in two reference solvents; the isomeric ionic liquid [i‐C₄mim][PF₆], 1‐butyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [C₄mim][PF₆]), and hexanes. RESULTS: As reaction medium, [i‐C₄mim][PF₆] was best among the three solvents. The initial reaction rate, the equilibrium conversion of 2‐phenylethanol and the half‐lifetime of the lipase in [i‐C₄mim][PF₆] medium were about 1.5, 1.2 and 3‐fold that obtained in [C₄mim][PF₆] medium, respectively. The lipase in [i‐C₄mim][PF₆] medium was recycled 10 times without substantial diminution in activity. CONCLUSION: The ionic liquid [i‐C₄mim][PF₆] has good biocompatibility, and can be used widely as green media in various biocatalysis reactions to improve the activity and stability of enzymes. Besides hydrophobicity and nucleophilicity, the spatial configuration of ionic liquids is also considered a key factor effecting the behaviour of the enzyme in ionic liquids. Copyright © 2008 Society of Chemical Industry     

Catalytic oxidation of 1,3-diisopropylbenzene using imidazolium ionic liquid as catalyst

Peroxidation of alkylaromatics is the key step in the synthesis of phenols. Different imidazolium ionic liquids were investigated for the oxidation of cumene. The selectivity of cumene hydroperoxide (CHP) increased with different ionic liquids in the order [C₄mim]Cl<[C₄mim]Br<[C₄mim]BF₄<[C₄mim]OH. This finding could be interpreted as being due to the partial decomposition of CHP by the acidic proton of the imidazolium cation. Thus [C₄mim]OH was chosen as the catalyst for the oxidation of 1,3-diisopropylbenzene to corresponding hydroperoxides and its derivatives. The catalytic performance of [C₄mim]OH was also better than that of the traditional catalyst NaOH. Furthermore, the effects of the operating variables were investigated and the mechanism was discussed.     

Extraction of scandium(III) using ionic liquids functionalized solvent impregnated resins

Ionic liquids (ILs) functionalized solvent impregnated resins (SIRs) were prepared using IL modified Merrified resin as the polymeric supports by impregnation of extractant for extraction of Sc(III). The ILs modified Merrifield resin were prepared via covalent anchoring of imidazolium salts onto Merrifield resin. The polymeric supports with imidazolium chloride group (RCl) and imidazolium hexafluorophosphate group (RPF₆) were characterized by FTIR, TGA, and elemental analysis. It was found that RCl and RPF₆ had tunable hydrophilicity and hydrophobicity, different acid stability, and swelling behaviors in solvents. The effect of Cyanex 923 extractant or [C₈mim][PF₆] IL impregnated on RCl and RPF₆ were studied. The results showed Cyanex 923 and [C₈mim][PF₆] exhibited stronger affinity to RPF₆ than to RCl. RPF₆ with Cyanex 923 was found to be effective in Sc(III) extraction. The extraction mechanisms of SIRs containing RPF₆ and Cyanex 923 with or without [C₈mim][PF₆] were cation exchange and neutral complexation, respectively. [C₈mim][PF₆] acted as an extraction media and was involved in the cation exchanged extraction reaction. Sc(III) can be selectively separated from Tm(III), Yb(III), and Lu(III) by the SIRs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Recovery of Furfural from Aqueous Solution by Ionic Liquid Based Liquid–Liquid Extraction

Abstract

Liquid–liquid extraction with imidazolium based ionic liquids ([C₄mim][PF₆], [C₆mim][PF₆], and [C₈mim][PF₆]) is proposed for the separation of furfural or 5-methylfurfural from aqueous solution. Factors affecting the extraction of furfural or 5-methylfurfural have been studied. It was shown that the extraction equilibria can be achieved within 30 min and the process was less affected by the factors such as volume ratio and feed concentration. The partition coefficients of furfural and 5-methylfurfural decreased with increasing temperature. [C₆mim][PF₆] was found to have the best extraction ability among the three ionic liquids studied. Presence of small amount of NaCl or Na₂SO₄ in the aqueous phase results in the considerable increase in the partition coefficients of furfural because of the competitive hydration of the salts with furfural. A thermodynamic study revealed that the extraction process was driven mainly by hydrophobic interactions. Further experimental results indicated that furfural can be separated selectively from aqueous furfural/acetic acid mixtures.     

Optimization of Enzymatic Synthesis of Tricaprylin in Ionic Liquids by Response Surface Methodology

Ten 1,3‐dialkylimidazolium‐based ionic liquids (ILs) have been investigated as media for the enzymatic synthesis of tricaprylin, in comparison with the conventional organic solvent hexane. The results suggested that the esterification activity of Novozym 435 was higher than Lypozyme RM IM in all the ILs assayed. Novozym 435 showed higher catalytic activity in ILs with anions Tf₂N^? and PF₆^? than in BF₄^? and hexane. FTIR analysis of the secondary structure of the lipase indicated that a smaller decrease of the α‐helix was observed in [C₄MIM] Tf₂N and [C₄MIM] PF₆ than [C₄MIM] BF₄ and hexane, indicating that the anions of ILs might be a key factor for the activity of lipase in ILs. Process parameters (amount of lipase, caprylic acid/glycerol molar ratio, temperature and their interactive effects) were optimized in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄MIM]PF₆) using Novozym 435 by response surface methodology. When the reactions were performed with the lipase amount of 6.1 % substrate mass at a caprylic acid/glycerol molar ratio of 4.5:1 and 66.7 °C, a higher yield was reached up to 92.4 %.     

Efficient Copper-bisisoquinoline-based Catalysts for Selective Aerobic Oxidation of Alcohols to Aldehydes and Ketones

The selective oxidation of alcohols with molecular oxygen was efficiently completed in high conversion and selectivity using copper-bisisoquinoline-based catalysts under mild reaction condition. The effects of various parameters such as reaction temperature, reaction time, oxidant, ligands, etc, were studied. Solvent effect has been as well studied in ionic liquids [bmim]PF₆, [omim]BF₄ and [hmim]BF₄, comparing to traditional volatile organic solvent. The use of ionic liquids was found to enhance the catalytic properties of the catalysts used.     

Reverse ATRP of acrylonitrile with diethyl 2,3-dicyano-2,3-diphenyl succinate/FeCl3/iminodiacetic acid

The reverse atom transfer radical polymerization (RATRP) technique using FeCl₃/iminodiacetic acid (IMA) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexa-substituted ethane thermal initiator, diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS), was firstly used as the initiator in this iron-based RATRP system. The polymerization in N,N-dimethylformamide not only shows the best control of molecular weight and its distribution but also provides rather rapid reaction rate with the ratio of [AN]:[DCDPS]:[FeCl₃]:[IMA] at 500:1:2:4. The rate of polymerization increases with increasing the polymerization temperature and the apparent activation energy was calculated to be 49.9 kJ mol⁻¹. The polymers obtained were end-functionalized by chlorine atom, and they were used as macroinitiators to proceed the chain extension polymerization in the presence of FeCl₂/IMA catalyst system via a conventional ATRP process. The resultant polyacrylonitrile fibers were obtained with the fineness at 1.16 dtex and the tenacity at 6.01cN dtex⁻¹.     

Separation of scandium(III) from lanthanides(III) with room temperature ionic liquid based extraction containing Cyanex 925

The separation of Sc(III) from Y(III), La(III) and Yb(III) in [C₈mim][PF₆] containing Cyanex 925 has been investigated, and is reported in this paper. A cation exchange mechanism of Sc(III) in [C₈mim][PF₆] and Cyanex 925 is proposed by study of the influence of anionic and cationic species on the extraction. The coefficient of the equilibrium equation of Sc(III) was confirmed by slope analysis of log D_Sc vs log [Cyanex 925], and the loading capacity also confirmed the stoichiometry of Cyanex 925 to Sc(III) was close to 3:1. Infrared data for Cyanex 925 saturated with Sc(III) in [C₈mim][PF₆] indicated strong interaction between P?O of Cyanex 925 and Sc(III). In addition, the relationship between log D_Sc and temperature showed that temperature had little influence on the extraction process, and the resulting thermodynamic parameters indicated that an exothermic process was involved. Copyright © 2007 Society of Chemical Industry     

Rhodium Acetate Dimer Immobilized in 1‐Butyl‐3‐methylimidazolium Hexafluorophosphate Ionic Liquid: a Novel and Recyclable Catalytic System for the Cyclopropanation of Alkenes

Alkenes undergo smooth cyclopropanation with ethyl diazoacetate using a catalytic amount of rhodium acetate dimer, Rh₂(OAc)₄, immobilized in the air‐ and moisture‐stable 1‐butyl‐3‐methylimidazolium hexafluorophosphate ionic liquid, [bmim]PF₆, to afford cyclopropanecarboxylates in excellent yields with high trans‐selectivity. The recovery of the catalyst is facilitated by the hydrophobic nature of [bmim]PF₆. The recovered ionic liquid containing Rh₂(OAc)₄ can be reused for three to five subsequent runs with only a gradual decrease in activity.     

Study on Dissolution and Regeneration of Poplar Wood in Imidazolium-Based Ionic Liquids

Abstract

We tested dissolution and regeneration of poplar wood using 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) and 1-butyl-3-methylimidazolium acetate ([C₄mim]OAc). When 5wt% of poplar sawdust in [C₄mim]OAc was stirred at 130°C, 96wt% of added poplar was dissolved in [C₄mim]OAc, whereas 25.3wt% of poplar dissolved in [C₄mim]Cl at the same reaction condition. Fourier transform infrared spectroscopy (FT-IR) and lignin content analysis revealed that poplar was partially delignified during the dissolution and regeneration processes. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and microscopy were used to characterize raw poplar sawdust, undissolved poplar, and regenerated wood from the poplar-ionic liquid solution. The direct acetylation of poplar-[C₄mim]OAc solution using acetyl chloride was also performed in the absence of any organic solvent. FT-IR analysis of the resulting wood sample revealed the formation of partially delignified acetylated-poplar.     

四氟硼酸盐类离子液体对典型柴油的萃取脱硫研究

The extractive removal of sulfur compounds （S-compounds） from Dongying and Liaohe diesel fuels with [BF4]^--based ionic liquids were systematically investigated. The results show that the absorption capacity of an ionic liquid for the S-compounds in diesel fuels relies on its structure and its size. In the case of the two examined diesel fuels, both elongating the cation tail length and increasing the mass ratio of ionic liquid/diesel fuel promote the desulfurization ability of the examined ionic liquids. The results also show that imidazolium-based ionic liquids display higher extraction efficiencies than pyridinium-based ionic liquids, presumably owing to the fact that the rings of the S-compounds are similar to the imidazolium head ring. With the 1 ： 1 mass ratio of ionic liquid/diesel fuel, the rates of the first desulfurization of Dongying and Liaohe diesel fuels using [C8mim][BF4] amount to 29.96% and 39.76%, suggesting that [C8mim][BF4] is a promising extractant for desulfurization of these diesel fuels.     

Cycloaddition of carbon dioxide to epichlorohydrin using ionic liquid as a catalyst

The cycloaddition of carbon dioxide to epichlorohydrin was performed without any solvent in the presence of ionic liquid as catalyst. 1-Alkyl-3-methyl imidazolium salts of different alkyl group (C₂, C₄, C₆, C₈) and anions (Cl⁻, BF₄⁻, Br⁻, PF₆⁻) were used for this reaction carried out in a batch autoclave reactor. The conversion of epichlorohydrin was affected by the structure of the imidazolium salt ionic liquid; the one with the cation of longer alkyl chain length and with more nucleophilic anion showed better reactivity. The conversion of epichlorohydrin increased as the temperature increased from 60°C to 140°C. It also increased with increasing carbon dioxide pressure probably due to the increase of the absorption of carbon dioxide into the mixture of epichlorohydrin and the ionic liquid. Zinc bromide was also tested for its use as a cocatalyst in this reaction. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Catalytic Activity of Pd(II) Complexes with Triphenylphosphito Ligands in the Sonogashira Reaction in Ionic Liquid Media

The reactivity of palladacycle dimeric complexes with substituted triarylphosphito ligands P(OR)₃ (R = Ph, m-MeC₆H₄, o-MeC₆H₄, C₆H₃-2,4-tBu₂) as well as their non-orthometallated analogues PdCl₂[P(OR)₃]₂ was tested in a copper-free Sonogashira reaction with iodobenzene and phenylacetylene as substrates and imidazolium ionic liquids as the reaction medium. The ionic liquids [bmim][PF₆], [bmim][BF₄] and [emim][SO₄Et] were chosen. The palladium complexes studied showed high activity, and the yield of diphenylacetylene ranged from 31 to 98% in 1 h. The best results were obtained in [bmim][PF₆] for PdCl₂[P(O-m-MeC₆H₄)₃]₂ (84%) and for orthopalladated dimer with the same phosphite (98%).     

An iron‐based reverse ATRP process for the living radical polymerization of acrylonitrile

A hexa‐substituted ethane thermal iniferter, diethyl‐2,3‐dicyano‐2,3‐di(p‐tolyl) succinate (DCDTS), was firstly used as the initiator in the reverse atom transfer radical polymerization (RATRP) of acrylonitrile. FeCl₃ coordinated by isophthalic acid (IA) was used as the catalyst in this system. The polymerization in N,N‐dimethylformamide not only shows the best control of molecular weight and its distribution but also provides rather rapid reaction rate with the ratio of [AN] : [DCDTS] : [FeCl₃] : [IA] at 500 : 1 : 2 : 4. The polymers obtained were end‐functionalized by chlorine atom, and they were used as macroinitiators to proceed the chain extension polymerization in the presence of FeCl₂/IA catalyst system via a conventional ATRP process and polyacrylonitrile obtained was with M_n = 39,260, PDI = 1.25. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Dye-Affinity Partitioning of Acidic,Basic, and Neutral Proteins in Ionic Liquid-Based Aqueous Biphasic Systems

The partitioning behavior of model acidic (bovine serum albumin, BSA), basic (hen egg white lysozyme, LYS), and neutral (horse heart myoglobin, MYO) proteins in ionic liquid-based aqueous biphasic systems containing Reactive Red-120 dye has been reported. This study found that partition coefficients of the proteins depended on their chemical structures, pH of the aqueous phase, temperature, and composition of the aqueous biphasic system. It was found that partition coefficients of proteins in aqueous biphasic system containing RR-120 were in the order of LYS > MYO > BSA. Recovery of the hydrophilic ionic liquid, [C₄mim]Br, was achieved by using hydrophobic ionic liquid, [C₄mim]PF_6.     

Deep Desulfurization of Gasoline Fuel using FeCl3-Containing Lewis-Acidic Ionic Liquids

The FeCl₃-containing Lewis-acidic ionic liquids (ILs) [C₆mim]Cl/FeCl₃(1:1.5), [C₆mim]Cl/FeCl₃(1:2), [C₈mim]Cl/FeCl₃(1:1.5), and [C₈mim]Cl/FeCl₃(1:2) were used as extractants for desulfurization of model fuel and gasoline fuel, respectively. The results demonstrate that these ILs are effective for the removal of sulfur compounds from model fuel under different mass ratio of IL to model fuel (1:1, 1:3, 1:5, 1:10) at 25°C. The extractive performance of ILs increased as the molar ratio of FeCl₃ to [C_nmim]Cl(n = 6, 8) varied from 1:1 to 1:2. The selectivity of sulfur compounds by extraction process followed the order of dibenzothiophene (DBT)>benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). The sulfur removal of gasoline fuel containing sulfur content of 440.3 ppmw could be up to 85.8%; that is to say that the sulfur content of gasoline fuel varied from 440.3 ppmw to 62.4 ppmw after one extraction stage. Moreover, the [C₆mim]Cl/FeCl₃(1:2) can be recycled for at least 4 times with a little decrease in the desulfurization activity.