Lewis Basic Ionic Liquids‐Catalyzed Conversion of Carbon Dioxide to Cyclic Carbonates

A series of easily prepared Lewis basic ionic liquids were developed for cyclic carbonate synthesis from epoxide and carbon dioxide at low pressure without utilization of any organic solvents or additives. Notably, quantitative yields together with excellent selectivity were attained when 1,8‐diazabicyclo[5.4.0]undec‐7‐enium chloride ([HDBU]Cl) was used as a catalyst. Furthermore, the catalyst could be recycled over five times without appreciable loss of catalytic activity. The effects of the catalyst structure and various reaction parameters on the catalytic performance were investigated in detail. This protocol was found to be applicable to a variety of epoxides producing the corresponding cyclic carbonates in high yields and selectivity. Therefore, this solvent‐free process thus represents an environmentally friendly example for the catalytic conversion of carbon dioxide into value‐added chemicals by employing Lewis basic ionic liquids as catalyst. A possible catalytic cycle for the hydrogen bond‐assisted ring‐opening of epoxide and activation of carbon dioxide induced by the nucleophilic tertiary nitrogen of the ionic liquid was also proposed.     

二氧化硫和二氧化碳在离子液体支撑液膜中的渗透率和选择性

Permeabilities and selectivities of gases such as carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen (N2) and methane (CH4) in six imidazolium-based ionic liquids ([emim][BF4], [bmim][BF4], [bmim][PF6], [hmim][BF4], [bmim][Tf2N] and [emim][CF3SO3]) supported on polyethersulfone microfiltration membranes are investigated in a single gas feed system using nitrogen as the environment and reference component at temperature from 25 to 45ºC and pressure of N2 from 100 to 400 kPa. It is found that SO2 has the highest permeability in the tested supported ionic liquid membranes, being an order of magnitude higher than that of CO2, and about 2 to 3 orders of magnitude larger than those of N2 and CH4. The observed selectivity of SO2 over the two ordinary gas components is also striking. It is shown experimentally that the dissolution and transport of gas components in the supported ionic liq-uid membranes, as well as the nature of ionic liquids play important roles in the gas permeation. A nonlinear in-crease of permeation rate with temperature and operation pressure is also observed for all sample gases. By considering the factors that influence the permeabilities and selectivities of CO2 and SO2, it is expected to develop an optimal supported ionic liquid membrane technology for the isolation of acidic gases in the near future.     

液膜分离二氧化碳气体的研究进展

简要回顾了分离二氧化碳气体的研究现状,分析了液膜种类、结构和传质过程,介绍了近年来改进液膜稳定性方面的发展,并展望了液膜分离二氧化碳气体的前景。     

Recent Developments and Applications of Ionic Liquids in Gas Separation Membranes

Flue gas emissions and the harmful effects of these gases urge to separate and capture these unwanted gases. Ionic liquids due to negligible vapor pressure, thermal stability, and wide electrochemical stability have expanded its application in gas separations. A comprehensive overview of the recent developments and applications of ionic liquid membranes (ILMs) for gas separation is given. The three general classifications of ILMs, such as supported ionic liquid membranes (SILMs), ionic liquid polymeric membranes (ILPMs), and ionic liquid mixed‐matrix membranes (ILMMMs) along with their applications, for the separation of various mixed gases systems is discussed in detail. Furthermore, issues, challenges, computational study, and future perspectives for ILMs are also considered.     

Improving Physical Adsorption of CO2 by Ionic Liquids‐Loaded Mesoporous Silica

CO₂ sorption capacities of the neat and silica‐supported 1‐butyl‐3‐methylimidazolium‐based ionic liquids (ILs) were measured under atmospheric pressure. The silica‐supported ILs were synthesized by the impregnation‐vaporization method and charactrized by N₂ adsorption/desorption and thermogravimeteric analysis (TGA). Evaluation of the effects of influential factors on sorption capacity demonstrated that by increase of the temperature, flow rate, and the weight percentage of ILs in sorbents, the sorption capacity decreases. Among the sorbents, [Bmim][TfO] and SiO₂‐[Bmim][BF₄](50) had the highest capacity. By increasing the IL portion in SiO₂‐[Bmim][BF₄], the selectivity for CO₂ to CH₄ could be improved. The CO₂‐rich sorbents could be easily recycled.     

Continuous Flow Enzymatic Kinetic Resolution and Enantiomer Separation using Ionic Liquid/Supercritical Carbon Dioxide Media

The combination of kinetic resolution in ionic liquids (IL) and selective extraction with supercritical carbon dioxide (scCO₂) provides a new approach for the separation of enantiomers as exemplified by the lipase‐catalyzed esterification of chiral secondary alcohols. Excellent enantioselectivities are achieved upon conversion of alcohols 1a–e to the corresponding acetates 4a–e or laureates 5a–e using various modifications of the lipase from Candida antarctica (CaL‐B) in imidazolium‐based ionic liquids. The anion of the ionic liquid has a significant influence on the performance of the bio‐catalyst with bis(trifluoromethanesulfonamide) [BTA] giving the best results. The acetates 4a–e can be extracted from the reaction mixture preferentially over the alcohols 1a–e with scCO₂ under certain conditions, but preparatively useful selectivities would require advanced multi‐step extraction procedures. In contrast, efficient separation is possible with relatively simple equipment if alcohols 1a–e are extracted preferentially from their corresponding laureates 5a–e . A “green” continuous process for the resolution of racemic alcohols without the use of organic solvents was devised on the basis of these findings.     

离子液体支撑液膜技术及其在气体分离中的研究进展

分析离子液体支撑液膜的气体分离机理,总结目前离子液体支撑液膜的制备方法以及不同膜材料、不同离子液体及其亲疏水性对离子液体支撑液膜稳定性的影响。介绍离子液体支撑液膜在气体分离中的应用,对离子液体支撑液膜的工业化前景进行了展望。     

离子液体在萃取分离中的应用

在查阅了大量的国内外文献资料的基础上,介绍了近几年离子液体研究应用的进展。综述了离子液体在萃取分离过程中的应用,并展望了离子液体在分离方面的应用前景和发展方向。     

离子液体膜材料分离二氧化碳的研究进展

离子液体由于具有不易挥发、结构可调、对CO₂有良好的吸收性能等特点而成为当前CO₂分离领域的研究热点,但因高黏度和高成本问题而限制了其工业化应用。将离子液体与气体分离膜材料结合,得到的新型分离膜材料兼具离子液体和膜的优势,成为当前离子液体研究领域的趋势之一。针对这一热点问题,综述了离子液体支撑液膜、聚离子液体膜和离子液体共混/杂化膜在CO₂分离方面的研究现状和进展,讨论了离子液体结构和含量对膜分离性能、稳定性等的影响。相关研究表明,离子液体共混/杂化膜具有较高的分离性能和稳定性,是一种很有应用前景的CO₂分离材料。提出该领域的重点发展方向,即开发新的功能化离子液体共混/杂化膜材料是解决高渗透通量与高稳定性之间矛盾、强化CO₂分离性能的有效途径,深入研究离子液体共混/杂化膜的形成机制、气体在膜中的渗透行为以及CO₂分离机理。     

离子液体在膜分离过程中的应用研究进展

介绍了离子液体(ionic liquids)是由有机阳离子和有机或无机阴离子构成的、在室温或室温附近温度下呈液体状态的盐类,是新兴的可替代挥发性有机化合物的绿色溶剂。阐述了离子液体具有熔点低、不易燃、低挥发性(蒸气压接近于零)、高导电能力、电化学窗口宽、可调节性强等独特性质;在二氧化碳、二氧化硫等酸性气体以及苯、环己烷等有机溶剂分离过程中有广泛应用前景。同时,介绍了含有双键等可聚合基团的一类离子液体-聚离子液体[poly(ionic liquid)s,PILs]在二氧化碳吸收方面有特殊表现,指出聚离子液体与聚偏氟乙烯(PVDF)共混得到的薄膜材料具有高稳定性、高机械强度以及高电导率,对于缓解能源匮乏以及环境污染等具有重大意义。     

富含二氧化碳的天然气分离及其利用

论述了国内外对富含二氧化碳的天然气分离技术的研究进展,包括：膜分离法、变压吸附（PSA）法、物理吸收法和化学吸收法等,并分析了天然气资源的深加工利用及其产品开发前景。     

Molecular dynamics simulation for the binary mixtures of high pressure carbon dioxide and ionic liquids简

Molecular dynamics simulation with an all-atom force field has been carded out on the two binary sys- tems of [bmim][PF6]-CO2 and [bmim][NO3]-CO2 to study the transport properties, volume expansion and micro- structures. It was found that addition of CO2 in the liquid phase can greatly decrease the viscosity of ionic liquids （ILs） and increase their diffusion coefficient obviously. Furthermore, the volume expansion of ionic liquids was found to increase with the increase of the mole fraction of CO2 in the liquid phase but less than 35% for the two simulated systems, which had a significant difference with CO2 expanded organic solvents. The main reason was that there were some void spaces inter and intra the molecules of ionic liquids. Finally, site to site radial distribution functions and corresponding number integrals were investigated and it was found that the change of microstructures of ILs bv addition CO2 had a great influence on the orooerties of ILs.     

Design of Ionic Phosphites for Catalytic Hydrocyanation Reaction of 3‐Pentenenitrile in Ionic Liquids†

The synthesis and characterization of a novel class of ionic phosphites bearing either a single cationic group obtained by quaternization of aminophosphites or three cationic groups prepared by reaction of phosphorus trichloride with imidazolium phenols are reported. The catalytic hydrocyanation reaction of 3‐pentenenitrile (3PN) into adiponitrile has been performed in the presence of Ni(0) with ionic phosphite ligands, and a Lewis acid in biphasic ionic liquid/organic solvent system. The screening of several original cationic phosphites was performed and the experimental conditions were optimized for the tri‐cationic phosphite tris‐4‐[(2,3‐dimethylimidazol‐1‐yl)methyl]phenyl phosphite tris[bis(trifluoromethylsulfonyl)amide]. It is possible to obtain performance similar to molecular systems and the catalyst and the Lewis acid were immobilized in the ionic phase.     

Absorption of Carbon Dioxide into Ionic Liquid of 2-Hydroxy Ethylammonium Lactate

Abstract

Absorption of carbon dioxide into organic solvents such as DMA, NMP, DMSO, and DMF with the 2-hydroxy ethylammonium lactate (HEAL) ionic liquid was investigated using a batch stirred tank with a plane of gas-liquid interface in a range of 0–2.0 kmol/m³ of HEAL and 298–318 K at 101.3 kPa. The absorption of CO₂ was analyzed with the film model accompanied by the zwitterion mechanism of CO₂ with HEAL. The proposed model fits the experimental data of the enhancement factor due to the ready, chemical absorption of CO₂ in different solvents, temperatures, and HEAL concentrations. The reaction rate constant of CO₂ with HEAL was correlated linearly with the solubility parameter of the solvent.     

膜法分离二氧化碳研究现状及发展趋势

从膜法气体分离的优点出发,阐述了膜法分离CO2的原理、工艺流程,并将其应用于分离烟道气中的CO2.介绍了几种常见的分离CO2的膜材料,针对现有膜材料的缺点,提出了改进方法,展望了膜法分离CO2的发展方向.     

Highly Perm-Selective Micro-Porous Hydrotalcite-Silica Membrane for Improved Carbon Dioxide-Methane Separation

A notable improvement of carbon dioxide (CO₂) adsorption in meso- and micro-porous membranes was observed when hydrotalcite (HT) was incorporated in the membranes. For carbon dioxide in carbon dioxide-methane (CH₄) mixture, HT-silica membrane successfully overcame the upper permeability/selectivity limitation for glassy and polymeric membranes, despite the absence of a solution-diffusion mechanism that is typically present in the glassy and polymeric membranes. The performance of HT-silica membrane was observed to exceed that of micro-porous silica and high performance zeolitic imidazolate framework (ZIF) membranes. Incorporating unnecessarily high HT content in silica membrane, however, caused the membrane to lose its molecular sieving capacity and resulted in reduced selectivity of the gas.     

Y型沸石/炭杂化膜的制备及其气体分离性能

以聚酰胺酸为前驱体,Y型沸石为掺杂物,经高温炭化制备了Y型沸石/炭杂化膜.通过纯组分气体(H2,CO2,O2,N2)的渗透实验对杂化膜的气体渗透性能进行测定,并使用透射电镜,X射线衍射对杂化膜的微结构进行表征.研究了沸石的含量以及炭化温度对杂化炭膜的气体渗透性能和微结构的影响.结果表明,随着膜内沸石含量的提高,Y型沸石/炭杂化膜的气体渗透性能明显提高,而随着炭化温度的升高,Y型沸石/炭杂化膜的渗透系数降低,选择性提高.与纯炭膜相比,Y型沸石/炭杂化膜在保持高O2N2选择性的前提下,其渗透性能显著提高.炭化温度为700℃,沸石含量为15%,Y型沸石/炭杂化膜O2的气体渗透系数为501 bareer,O2/N2选择性为15.6.当炭化温度超过800℃以后,杂化膜中的沸石晶体结构被破坏,其气体渗透系数接近纯炭膜的气体渗透系数.因此,保持沸石孔道结构的完整是制备高性能沸石/炭杂化膜的关键因素之一.     

Selective Separation of Toluene/n‐Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4]

Room‐temperature ionic liquids serve as alternative solvents for volatile organic compounds in liquid‐liquid extraction and liquid membrane separation. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was applied for extraction and supported ionic liquid membranes (SILMs) to separate toluene and n‐heptane. A high separation factor of toluene was achieved due to the strong interaction between ionic liquid cations and toluene. The mass transfer performance of the SILM process was enhanced by higher operating temperature. With the increase of initial toluene concentration in the feed phase, the mass transfer flux and removal efficiency of the SILM process were improved, while the separation factor decreased. The mass transfer flux was growing with the increase of flow rate at both sides. The SILM process was stable over a long time period due to the high viscosity and low volatility of [Bmim][BF₄].