离子液体及离子液体膜在天然气净化方面的应用

天然气净化对天然气这一清洁、高效的一次能源及我国快速增长的消费需求具有重要的战略意义。离子液体因挥发性低、溶解能力强、结构和性质可调控性强等优点,在离子液体膜净化气体方面获得高度关注。本文系统地总结了离子液体膜富集分离CO₂及其他气体的性能,包括常规离子液体、功能化离子液体、聚合物离子液体、离子液体混合物;讨论了离子液体结构(如阳离子取代基链长、取代基对称性、阴离子结构大小、阴离子氟化)、膜支撑材料性能(如水溶性、孔径大小)及水含量等因素对膜性能的影响;对各种方法的优缺点及使用条件进行详细的阐述;并提出今后离子液体膜在气体净化方面的发展方向。     

离子液体在气体分离中的应用

离子液体是一类“可设计溶剂”,具有极低的蒸气压,几乎不挥发以及选择性溶解能力,近年来在气体分离领域得到了广泛的关注。本文综述了CO₂和SO₂等酸性气体、低碳链烷烃、烯烃和炔烃等有机气体,以及H₂、O₂、CO、N₂、Ar、Xe等其他气体在离子液体中的溶解性能,归纳了气体在离子液体中的溶解机理和溶解规律,分析了离子液体结构与溶解度、分离性质的定性关系,其中具有胺基、胍基等碱性基团的功能化离子液体对CO₂、SO₂等酸性气体具有良好的溶解性,含有不饱和基团的离子液体通过π-π相互作用可以改善烯烃在离子液体中的溶解度,炔烃则易溶于氢键碱性较强的离子液体;并介绍了离子液体/气体二元体系分子模拟、溶解度关联模型以及离子液体固定化用于气体分离等工作的研究进展,探讨了离子液体气体分离研究存在的问题和未来发展方向。     

离子液体在CO_2捕集中的应用进展

离子液体具有蒸汽压极低、热稳定性好、热容低和可以根据目标需求进行设计等特性,能克服传统CO2捕集工艺的诸多不足,因而成为目前CO2捕集溶剂的研究热点。本文主要综述了普通离子液体、功能化离子液体、支撑型离子液体膜、聚合型离子液体和离子液体复配溶液在CO2捕集方面的应用研究进展,评述了各种方法的优势和缺点,并在此基础上提出...     

离子液体捕集CO2

CO₂是导致温室效应的最主要成分,因此碳捕集技术的研究受到学术界和产业界的高度重视。离子液体具有不挥发、不燃烧、热稳定性好、溶解能力强、结构和性质可调节并可循环使用等特性,在CO₂的吸收/分离领域展现了广阔的应用前景。本文系统地综述了近年来常规离子液体、功能化离子液体、支撑离子液体膜、聚合离子液体以及离子液体与分子溶剂的混合物在捕集CO₂方面的研究进展;讨论了离子液体的阳离子结构、阴离子类型、烷基链长度、阴/阳离子的氟化程度和功能化、离子液体的负载作用和聚合效应以及体系的温度和压力对CO₂选择性捕集性能的影响;分析了可能的捕集机理以及各种捕集方法的优点和缺点;提出了目前需要进一步研究的若干重要问题,并对其发展前景进行了展望。     

支撑液膜研究及应用进展

支撑液膜技术是高选择性膜分离技术,本文对支撑液膜分离技术的研究进展进行了回顾,详述了用于金属离子分离的支撑液膜所采用的载体、影响支撑液膜稳定性的原因以及改善途径,并对支撑液膜的发展前景进行了展望。     

CO2选择性透过膜材料的制备

作为一种主要温室气体和一种重要的"潜在碳资源",CO2的分离和回收备受关注.与传统的CO2分离方法相比,膜分离技术具有不可比拟的优势.本文对近年来CO2选择透过无机膜、聚合物膜和促进传递膜等膜材料的制备方法及改性研究进行了综述,并对CO2选择性透过膜材料未来的发展进行了展望.     

离子液体催化CO2与环氧化物合成环状碳酸酯

综述了离子液体催化CO2与环氧化物的环加成反应制备环状碳酸酯的研究进展。目前报道的离子液体主要包括咪唑盐、季铵盐、季鏻盐等。对比了传统离子液体与功能化离子液体对CO2环加成反应的催化活性、选择性以及催化作用机制。与传统的离子液体相比,功能化离子液体的羟基或羧基等官能团与卤素离子等Lewis碱之间存在协同效应,使得其对CO2与环氧化物的环加成反应具有更好的催化活性;将功能化离子液体固载于无机材料(SiO2,SBA-15,MCM-41等)或聚合物所得的多相催化剂不仅保持了官能团与阴离子之间的协同效应,而且载体与离子液体活性组分之间也显示出协同效应,使得该类催化剂具有很好的催化活性,稳定性好,可以多次重复使用,具有较好的工业化前景,是值得深入研发的一类催化材料。此外,离子液体对于手性环状碳酸酯的合成也具有较好的催化活性和立体选择性。     

离子液体在乙烯/乙烷和乙烯/乙炔分离中的应用

乙烯,作为石油化工行业的龙头原料,其高效回收分离具有重要的战略意义。离子液体作为一种结构可调控的新型绿色溶剂,在乙烯的回收分离中展现出巨大的应用前景。本文总结了近年来离子液体在乙烯/乙烷和乙烯/乙炔分离方面的研究进展,从溶剂吸收、膜吸收和与多孔材料相结合的吸附分离法等角度展开,系统地阐述了常规离子液体、功能化离子液体、聚离子液体等纯组分体系及多组分体系在不同分离方法中的研究现状,展望了离子液体在乙烯回收分离方面的应用前景和发展趋势。     

离子液体在萃取和液膜过程中的应用研究新进展

介绍了近几年离子液体在萃取和液膜分离过程中研究应用的新进展,并展望了离子液体在分离科学应用的前景和发展方向。引用文献56篇。     

咪唑基离子液体固定分离CO2的研究进展

以咪唑基离子液体为代表,综述了近期普通咪唑基离子液体、功能咪唑基离子液体、支撑咪唑基离子液体和聚合咪唑基离子液体在分离固定CO2方面的研究进展,说明了各类咪唑基离子液体分离固定CO2的可行性及优缺点,并总结了离子液体固定CO2的影响因素和分离机制.     

Theoretical and experimental correlations of gas dissolution, diffusion, and thermodynamic properties in determination of gas permeability and selectivity in supported ionic liquid membranes

Supported ionic liquid membranes (SILMs) has the potential to be a new technological platform for gas/organic vapour separation because of the unique non-volatile nature and discriminating gas dissolution properties of room temperature ionic liquids (ILs). This work starts with an examination of gas dissolution and transport properties in bulk imidazulium cation based ionic liquids [C(n)mim][NTf2] (n=2.4, 6, 8.10) from simple gas H(2), N(2), to polar CO(2), and C(2)H(6), leading to a further analysis of how gas dissolution and diffusion are influenced by molecular specific gas-SILMs interactions, reflected by differences in gas dissolution enthalpy and entropy. These effects were elucidated again during gas permeation studies by examining how changes in these properties and molecular specific interactions work together to cause deviations from conventional solution-diffusion theory and their impact on some remarkably contrasting gas perm-selectivity performance. The experimental perm-selectivity for all tested gases showed varied and contrasting deviation from the solution-diffusion, depending on specific gas-IL combinations. It transpires permeation for simpler non-polar gases (H(2), N(2)) is diffusion controlled, but strong molecular specific gas-ILs interactions led to a different permeation and selectivity performance for C(2)H(6) and CO(2). With exothermic dissolution enthalpy and large order disruptive entropy, C(2)H(6) displayed the fastest permeation rate at increased gas phase pressure in spite of its smallest diffusivity among the tested gases. The C(2)H(6) gas molecules "peg" on the side alkyl chain on the imidazulium cation at low concentration, and are well dispersed in the ionic liquids phase at high concentration. On the other hand strong CO(2)-ILs affinity resulted in a more prolonged "residence time" for the gas molecule, typified by reversed CO(2)/N(2) selectivity and slowest CO(2) transport despite CO(2) possess the highest solubility and comparable diffusivity in the ionic liquids. The unique transport and dissolution behaviour of CO(2) are further exploited by examining the residing state of CO(2) molecules in the ionic liquid phase, which leads to a hypothesis of a condensing and holding capacity of ILs towards CO(2), which provide an explanation to slower CO(2) transport through the SILMs. The pressure related exponential increase in permeations rate is also analysed which suggests a typical concentration dependent diffusion rate at high gas concentration under increased gas feed pressure. Finally the strong influence of discriminating and molecular specific gas-ILs interactions on gas perm-selectivity performance points to future specific design of ionic liquids for targeted gas separations.     

Liquid membranes for gas/vapor separations

A review on developments of liquid membranes (LMs) in the field of gas and vapor separation of the last 16 years is presented. Liquid membrane configurations employing supports, i.e. immobilized, supported and contained liquid membranes are focussed and detailed information on the respective materials, i.e. supports (supplier, type, thickness, pore width, porosity, tortuosity), liquids and carriers, are presented together with their specific separation tasks. Performance of different LMs in terms of permeability and selectivity as well as stability (duration of testing, applied differential pressures) are compared and discussed. Finally, different preparation methods of LMs are illustrated.     

Conventional processes and membrane technology for carbon dioxide removal from natural gas:A review

Membrane technology is becoming more important for CO 2 separation from natural gas in the new era due to its process simplicity,relative ease of operation and control,compact,and easy to scale up as compared with conventional processes.Conventional processes such as absorption and adsorption for CO 2 separation from natural gas are generally more energy demanding and costly for both operation and maintenance.Polymeric membranes are the current commercial membranes used for CO 2 separation from natural gas.However,polymeric membranes possess drawbacks such as low permeability and selectivity,plasticization at high temperatures,as well as insufficient thermal and chemical stability.The shortcomings of commercial polymeric membranes have motivated researchers to opt for other alternatives,especially inorganic membranes due to their higher thermal stability,good chemical resistance to solvents,high mechanical strength and long lifetime.Surface modifications can be utilized in inorganic membranes to further enhance the selectivity,permeability or catalytic activities of the membrane.This paper is to provide a comprehensive review on gas separation,comparing membrane technology with other conventional methods of recovering CO 2 from natural gas,challenges of current commercial polymeric membranes and inorganic membranes for CO 2 removal and membrane surface modification for improved selectivity.     

Determination of the upper limits, benchmarks, and critical properties for gas separations using stabilized room temperature ionic liquid membranes (SILMs) for the purpose of guiding future research

The literature reports that supported ionic liquid membranes (SILMs) outperform standard polymers for the separations of CO₂/N₂ and CO₂/CH₄, even under continuous flow mixed gas conditions. Before the expenditure of more resources to develop new room temperature ionic liquids (RTILs) and SILMs, it is time to consider what benchmarks for SILM performance exist and if upper limits could be projected based on the physical chemistry of RTILs. At this juncture, we should ask if the current research efforts are properly focused based on the successes and failures in the literature. We summarize literature data, along with adding new data, on the SILM permeabilities and selectivities for the following gas pairs: CO₂/N₂, CO₂/CH₄, O₂/N₂, ethylene/ethane, propylene/propane, 1-butene/butane, and 1,3-butadiene/butane. The analysis predicts a maximum CO₂-permeability for SILMs and an upper bound for permeability selectivity vs. CO₂-permeability with respect to the CO₂/N₂ and CO₂/CH₄ separations. Also summarized are the representative successes and failures for improving the separation performance of SILMs via functionalization and facilitated transport in the context of the CO₂/N₂, CO₂/CH₄, and olefin/paraffin separations. In the context of the CO₂-separations, the analysis recommends a number of future research foci including research into SILMs cast from RTILs with smaller molar volumes. In the context of olefin/paraffin separations, the preliminary data is encouraging when considering the use of facilitated transport via silver carriers. Since RTIL-solvent/solvent interactions dominate in terminating the overall SILM performance, past attempts at enhancing solute/solvent interactions via the addition of functional groups to the RTILs have not produced SILMs with better separation performance compared to the unfunctionalized RTILs. Future research into functionalized RTILs needs to consider the changes to the dominant solvent/solvent interactions and not just the solute/solvent interactions.     

Micelles in Separations: Practical and Theoretical Review

This paper presents a brief overview of improved Liquid membrane (LM) separation techniques. including modified bulk, supported and emulsion liquid membranes as well as hollow fibre contained liquid membranes, electrostatic pseudo liquid membranes (ESPLIM) reverse micelle and recently developed hybrid (HLM) and other LM configurations. The discussion also includes design of ion specific carriers, analytical importance, aspects of stability and modelling of LMs and their applications in the separation/removal of metal captions from a range of diverse matrices. In general, an attempt has been made to review the literature published from 1990 to 1997 in order to focus on the present status of different liquid membrane configurations. The LM studies dealing with separation and removal of organic compounds and gases are not included in this article owing to limitations of space.     

On-line sample preconcentration in capillary electrophoresis, focused on the determination of proteins and peptides

This overview highlights the possibilities of on- or in-line preconcentration procedures in combination with a CZE separation, focused on the determination of peptides and proteins. The discussed methods, including sample stacking, field-amplified injection, isotachophoresis, solid phase extraction, membrane preconcentration, electroextraction, supported liquid membranes, hollow fibers, immunoaffinity, and molecularly imprinted polymers technology preconcentration are categorized in electrophoresis-based and chromatography-based preconcentration. The chromatography-based preconcentration is subdivided in low-specificity and high-specificity methods. A number of preconcentration methods are available, however, this paper demonstrates that various compounds in different media (aqueous solutions, urine, and plasma) require different preconcentration systems. The preconcentration techniques of first choice in general seem to be solid-phase extraction and membrane preconcentration, because of their high concentration ability, multiapplicability, relative simplicity and clean-up capability. For the future, hollow fibers seem to hold a great potential as preconcentration technique, yielding high concentration factors, using simple designs. New techniques, such as hollow fibers, molecularly imprinted polymers technology and supported liquid membranes may have the potential to supersede the conventional preconcentration techniques in some cases. The larger the arsenal of preconcentration techniques becomes, the more efficiently peptides and proteins may be analyzed in the future. These techniques, in some cases, require pre-cleanup procedures, to ensure the purity of the samples to concentrate.     

High temperature separation of carbon dioxide/hydrogen mixtures using facilitated supported ionic liquid membranes

Efficiently separating CO₂ from H₂ is one of the key steps in the environmentally responsible uses of fossil fuel for energy production. A wide variety of resources, including petroleum coke, coal, and even biomass, can be gasified to produce syngas (a mixture of CO and H₂). This gas stream can be further reacted with water to produce CO₂ and more H₂. Once separated, the CO₂ can be stored in a variety of geological formations or sequestered by other means. The H₂ can be combusted to operate a turbine, producing electricity, or used to power hydrogen fuel cells. In both cases, only water is produced as waste. An amine-functionalized ionic liquid encapsulated in a supported ionic liquid membrane (SILM) can separate CO₂ from H₂ with a higher permeability and selectivity than any known membrane system. This separation is accomplished at elevated temperatures using facilitated transport supported ionic liquid membranes.