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...     

非平衡热力学在界面传递过程中的应用

21世纪以来，随着各学科之间的交叉渗透，化学工程的研究对象越来越复杂，界面传递对多相化工过程的影响越来越显示出它的重要性，传统的传递模型已经很难对界面复杂动态的传递行为进行定量描述．本文应用线性非平衡态热力学理论，对传统物质传递模型进行描述，分析界面传递过程速率，强化的三个因素：界面传质系数K、传递截面积A、界面化学位梯度△u．以含钾化合物作为模型体系，基于非平衡热力学原理建立了描述和预测固一液界面处介质传递速率的模型，并建立了描述其溶解速率的通用模型和测定钾离子动力学数据的实验方法，通过分析探讨了多相过程速率强化的途径．     

以离子液体为介质的H_2S捕集与转化研究进展

从能源气中脱除硫化氢(H_2S)是能源化工的基础工艺,具有重要的科学和现实意义.离子液体是一类在室温附近呈液态的有机熔融盐,可用作捕集H_2S的新型介质.综合国内外学者和本课题组在该领域内的多年研究积累,本文介绍了H_2S在离子液体中的捕集和转化研究进展,讨论了捕集与转化流程工艺,并分析了当前离子液体用于H_2S捕集与转化的发展趋势.     

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。     

膜吸收-再生循环技术捕集CO_2操作性能及其参数优化研究

采用N-甲基二乙醇胺(MDEA)+哌嗪(PZ)复合溶液作为捕集CO2吸收剂,研究了膜吸收-再生循环装置的操作性能,考察了气液流量、吸收剂浓度和再生电压等因素对捕集率和传质通量的影响,采用正交实验方法,优化操作条件,确定最佳操作方案。结果表明,气体流量对捕集率的影响明显大于液体流量的影响;气体流量增大对传质通量影响不明显;吸收剂浓度的增大使传质通量迅速增大,但大于一定值时通量不再增大;正交实验得出最佳操作条件为液体流量110 mL/min、气体流量0.65 L/min、吸收剂总浓度2.5 mol/L和再生电压210 V,捕集率大于95%,传质通量维持在5.86×10-4mol/(m2.s)。     

离子液体的黏度与其扩散系数和电导率的新型关系方程

离子液体的传递性质对其在化学化工等领域的研究和应用至关重要,但迄今文献中缺乏可靠的理论预测模型或传递性质间的相互关系式,因此,有必要建立传递性质间的相互关系以便应用.本文建立了离子液体黏度与扩散系数或电导率间的定量关系,并利用文献实验数据进行了系统检验.结果表明,新方程可由离子液体黏度数据准确预测其扩散系数和电导率.与Stokes-Einstein方程相比,新方程不仅可解释离子液体中的许多实验现象,而且实现了定量预测(无需离子的有效流体力学半径数据).     

离子液体的制备及应用*

离子液体由于具有独特的物理化学性质而成为一种新型的绿色溶剂,近年来成为国际上研究的前沿和热点。它为开发新型绿色工艺、实现传统重污染、高能耗工业过程的升级换代提供了新机遇。本文介绍了离子液体的合成与制备方法,以及离子液体在CO2捕集分离及转化利用、电解/电镀铝、SO2吸收、废水处理以及废旧塑料降解循环利用中的应用,展望了离子液体的发展前景。     

功能离子液体[NH2p-bim]BF4吸收CO2的密度泛函研究

用密度泛函理论对功能化离子液体[NH2p-bim]BF4吸收CO2的作用机制进行了理论研究。在RB3LYP/6-311 G**的计算水平对离子液体[NH2p-bim]BF4的结构以及CO2与该离子液体反应可能生成的产物进行了全优化,获得了优化结构的振动频率和热力学数据。计算结果表明,离子液体[NH2p-bim]BF4吸收CO2主要是通过离子液体的阳离子[NH2p-bim] 自偶解离的[NHp-bim]与CO2分子结合生成[O2C-NHp-bim],其结合能为238-260 kJ/mol。     

无机盐活化剂一氨基酸盐基溶液捕集温室气体CO2

将无机盐K3PO4、K2HPO4和KH2PO4作为活化剂,分别添加于氨基乙酸盐溶液中,形成CO2活化吸收剂,采用膜接触器-再生循环装置,评价和比较了氨基乙酸盐和活化吸收剂捕集CO2的性能,研究了活化剂的浓度、气液流速等因素对总体积传质系数、传质通量和捕集率的影响。结果表明,磷酸盐活化剂在氨基乙酸盐吸收剂中,对CO2的捕集均产生影响,活化效应存在PO4^3-〉HPO4^2-〉H2PO4^-的规律;添加少量活化剂的作用比添加较多量的活化作用大;活化吸收剂的捕集率明显大于非活化吸收剂;膜吸收流体力学状态的改变,能够改善膜接触器传质性能,增大传质通量,但增大的程度有限。     

CO2/离子液体体系热力学性质的分子动力学模拟

超临界CO2和离子液体(ILs)是两种绿色溶剂. 离子液体可以溶解超临界CO2, 而超临界CO2不能溶解离子液体. 由此设计构成的CO2/IL二元系统, 同时具备了超临界CO2和离子液体的许多优点: 既可以降低离子液体的粘度, 还便于相分离, 是新型的耦合绿色溶剂. 其物理化学性质对于设计反应、分离等过程非常重要. 因此, 本文以CO2/IL二元系统为研究对象, 通过选择合适的分子力场和系综, 运用分子动力学(MD)模拟方法研究了CO2/[bmim][PF6]、CO2/[bmim][NO3]等体系的热力学性质. 结果表明, CO2对ILs膨胀度的影响非常小, 当CO2摩尔分数为0.5时, ILs膨胀仅为15%. CO2/ILs的扩散系数远小于CO2膨胀甲醇、乙醇溶液的扩散系数. 随着CO2含量的增加, ILs的扩散系数提高, 粘度显著下降, 表明CO2能有效地改善ILs扩散性, 减小其粘度. 因此CO2可用以改善离子液体溶剂体系的传递特性, 增强反应分离过程在其中的进行.     

Carbon dioxide capture by aminoalkyl imidazolium-based ionic liquid: a computational investigation

Efficient technologies/processes for CO(2) capture are greatly desired, and ionic liquids are recognized as promising materials for this purpose. However, the mechanisms for selectively capturing CO(2) by ionic liquids are unclear. In this study, the interactions between CO(2) and 1-n-amino-alkyl-3-methyl-imidazolium tetrafluoroborate, an amino imidazolium ionic liquid (AIIL), in its CO(2) capturing process, are elucidated with both quantum chemistry and molecular dynamics approaches on the molecular level. The effects of the straight aminoalkyl chain length in imidazolium-based cations on CO(2) capture are explored, and thereby the factors governing CO(2) capture for this ionic liquid family, e.g., ionic liquid structure, charge distribution, intermolecular interactions, thermodynamic properties and absorption kinetics, are analyzed. Molecular dynamics simulations are used to study the diffusion of the involved compounds and liquid structures of the CO(2)-AIIL systems. The results show that the amino-alkyl chain length plays an important role in governing the absorption properties of AIILs, including the free energies of absorption, equilibrium constants, desorption temperature, absorption rate constants, diffusion coefficients, and organization of CO(2) around cations and anions. This study provides useful information about rational design of ionic liquids for efficient CO(2) capture.     

CO2 Capture technologies: Current status and new directions using supported ionic liquid phase (SILP) absorbers

Current state-of-the-art techniques for CO2 capture are presented and discussed. Post-combustion capture of CO2 by absorption is the technology most easily retrofitted to existing installations, but at present this is not economically viable to install and run. Using ionic liquids instead of aqueous amine solutions overcomes the major thermodynamic issues. By applying SILP technology further advances, in terms of ease of handling and sorption dynamics, are obtained. Initial experimental studies showed that ionic liquids such as tetrahexylammonium prolinate, [N6666][Pro], provide a good candidate for CO2 absorption using SILP technology. Thus a solid SILP absorber comprised of 40 wt% [N6666][Pro] loaded on precalcined silica quantitatively takes up about 1.2 mole CO2 per mole of ionic liquid in consecutive absorption-desorption cycles in a flow-experiment performed with 0.09 bar of CO2 (9% CO2 in He).     

Tuning the physicochemical properties of diverse phenolic ionic liquids for equimolar CO2 capture by the substituent on the anion

Phenolic ionic liquids for the efficient and reversible capture of CO(2) were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO(2)-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO(2)-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, these ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO(2) capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO(2)-capture. This CO(2) capture process using diverse phenolic ionic liquids is a promising potential method for CO(2) absorption with both high absorption capacity and good reversibility.     

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.     

Improving carbon dioxide solubility in ionic liquids

Previously we showed that CO2 could be used to extract organic molecules from ionic liquids without contamination of the ionic liquid. Consequently a number of other groups demonstrated that ionic liquid/CO2 biphasic systems could be used for homogeneously catalyzed reactions. Large differences in the solubility of various gases in ionic liquids present the possibility of using them for gas separations. More recently we and others have shown that the presence of CO2 increases the solubility of other gases that are poorly soluble in the ionic liquid phase. Therefore, a knowledge and understanding of the phase behavior of these ionic liquid/CO2 systems is important. With the aim of finding ionic liquids that improve CO2 solubility and gaining more information to help us understand how to design CO2-philic ionic liquids, we present the low- and high-pressure measurements of CO2 solubility in a range of ionic liquids possessing structures likely to increase the solubility of CO2. We examined the CO2 solubility in a number of ionic liquids with systematic increases in fluorination. We also studied nonfluorinated ionic liquids that have structural features known to improve CO2 solubility in other compounds such as polymers, for example, carbonyl groups and long alkyl chains with branching or ether linkages. Results show that ionic liquids containing increased fluoroalkyl chains on either the cation or anion do improve CO2 solubility when compared to less fluorinated ionic liquids previously studied. It was also found that it was possible to obtain similar, high levels of CO2 solubility in nonfluorous ionic liquids. In agreement with our previous results, we found that the anion frequently plays a key role in determining CO2 solubility in ionic liquids.