关于限域离子液体吸附CO_2的密度泛函理论(DFT)的研究

近年来,温室效应日趋严重,因此吸收CO_2的材料受到了广泛的关注.采用了密度泛函理论(DFT)研究以SiO_2为载体的限域离子液体对CO_2的吸附.对比纯净离子液体(ILs)以及限域离子液体与CO_2的相互作用情况,在这两种状态下两种体系的吸附情况大不相同.从几何结构、相互作用以及电荷分析等方面对ILs、 SiO_2以及ILs/SiO_2复合结构进行研究.计算结果表明,载体、离子液体和CO_2之间都存在较强的相互作用.离子液体的负载不仅改变了SiO_2载体的结构,而且受载体的影响阴阳离子之间的相互作用力也发生了改变.计算结果为进一步深入限域离子液体对CO_2的吸附打下了理论基础.     

Prediction of Density,Surface Tension,and Viscosity of Quaternary Ammonium-Based Ionic Liquids ([N222(n)]Tf2N) by Means of Artificial Intelligence Techniques

In this work, thermophysical properties of quaternary ammonium-based ionic liquids (ILs) including density, surface tension, and viscosity are produced by two powerful artificial intelligence techniques: genetic function approximation (GFA) and artificial neural network (ANN). In proposed GFA and ANN models, the critical temperature and water content of studied ILs ([N_222(n)]Tf₂N with n = 5, 6, 8, 10, and 12) as well as operation temperature were given as the input parameters and the density, surface tension, and viscosity were predicted as the output results. The obtained results reveal that the selected input parameters are appropriate for prediction of thermophysical properties of quaternary ammonium-based ILs. In addition, the high statistical quality represented by various criteria and the low prediction errors of the presented models indicate that they can accurately predict the density, surface tension, and viscosity of new ILs without recourse to experimental data.     

含CO2/离子液体系统相行为及其在反应与分离中的应用进展

目前已知的绿色溶剂主要包括超临界流体（Supercritical fluids,SCFs）、离子液体（Ionic liquids,ILs）、二氧化碳膨胀液体（CO₂ expanded liquids, CXLs）、水以及上述溶剂的混合物等。其中,由超临界CO₂（Supercritical CO₂,SCCO₂）与ILs混合而构成的新兴溶剂,因为化学热力学方面的特性,成为近年来研究的热点,未来很有发展前景。本文回顾了目前为止在该领域所开展的工作,总结了影响SCCO₂与IL相行为的主要因素。包括温度、压力、ILs的含水量、ILs的阴离子、ILs的阳离子、ILs的摩尔体积以及助溶剂等。同时分析了ILs/SCCO₂与溶质形成的多元混合物相行为的成因。介绍了ILs/CO₂在萃取、反萃取、膜分离、反胶束、萃取与反应耦合等分离方面的应用。由于传统的单元操作很难满足无污染和对过程集成的要求,因而含有ILs/ SCCO₂的分离反应耦合过程将是未来是实现清洁生产的发展方向。     

Application of Task-specific Ionic Liquids for Intensified Separations

Summary. Ionic liquids offer tremendous opportunities to intensify reactions and separations in process technologies by tuning their physical and chemical properties. Several ionic liquids are suitable for the separation of aromatic and aliphatic hydrocarbons. CO₂ absorption behavior was influenced by the functionalized chains appended to the room temperature ionic liquid (RTIL) cation. Ionic liquids seem able to combine the chemical features of amine solutions with the characteristic advantages of the physical solvents used for CO₂ absorption.     

Elucidation of the Roles of Ionic Liquid in CO2 Electrochemical Reduction to Value-Added Chemicals and Fuels

The electrochemical reduction of carbon dioxide (CO₂ER) is amongst one the most promising technologies to reduce greenhouse gas emissions since carbon dioxide (CO₂) can be converted to value-added products. Moreover, the possibility of using a renewable source of energy makes this process environmentally compelling. CO₂ER in ionic liquids (ILs) has recently attracted attention due to its unique properties in reducing overpotential and raising faradaic efficiency. The current literature on CO₂ER mainly reports on the effect of structures, physical and chemical interactions, acidity, and the electrode–electrolyte interface region on the reaction mechanism. However, in this work, new insights are presented for the CO₂ER reaction mechanism that are based on the molecular interactions of the ILs and their physicochemical properties. This new insight will open possibilities for the utilization of new types of ionic liquids. Additionally, the roles of anions, cations, and the electrodes in the CO₂ER reactions are also reviewed.     

Spontaneous Formation of Nano-Emulsions Containing Task-Special Ionic Liquid and CO2 Capture in this Nano-Emulsions System

Nano-emulsions containing task-special ionic liquid ([NH₂ebim][PF₆]) were prepared by spontaneous emulsification. The stability of nano-emulsions was investigated by analysis of droplet size. The microstructure of the mixed solvent including the Triton X-100, n-butanol, and [NH₂ebim][PF₆] was demonstrated based on macular dynamic simulation. The results indicate that nano-emulsions are relatively stable to the droplet growth at static storage, but unstable under high centrifugal force. Simulation results from the macular dynamic calculation show that [NH₂ebim][PF₆] locates in the hydrophobic layer of Triton X-100 and n-butanol, which is available for enhancing CO₂ mass transfer in an absorption process. Nano-emulsions were used as the absorbent to absorb CO₂ in absorption experiments, and the absorption rates were investigated. The results show that nano-emulsion containing [NH₂ebim][PF₆] can enhance CO₂ absorption rate compared to the system that pure water was used as the absorbent. The reason is attributed to the reversible chemical reaction between [NH₂ebim][PF₆] and CO₂ on the interface of oil and water, which decreases the concentration of CO₂ in the bulk so as to increase the mass transfer driving force between gas and liquid. Therefore, the chemical reaction on the interface of oil and water promotes the absorption process.     

Monte Carlo Simulation and Experimental Studies of CO2, CH4 and Their Mixture Capture in Porous Carbons

Adsorption of carbon dioxide and methane in porous activated carbon and carbon nanotube was studied experimentally and by Grand Canonical Monte Carlo (GCMC) simulation. A gravimetric analyzer was used to obtain the experimental data, while in the simulation we used graphitic slit pores of various pore size to model activated carbon and a bundle of graphitic cylinders arranged hexagonally to model carbon nanotube. Carbon dioxide was modeled as a 3-center-Lennard-Jones (LJ) molecule with three fixed partial charges, while methane was modeled as a single LJ molecule. We have shown that the behavior of adsorption for both activated carbon and carbon nanotube is sensitive to pore width and the crossing of isotherms is observed because of the molecular packing, which favors commensurate packing for some pore sizes. Using the adsorption data of pure methane or carbon dioxide on activated carbon, we derived its pore size distribution (PSD), which was found to be in good agreement with the PSD obtained from the analysis of nitrogen adsorption data at 77 K. This derived PSD was used to describe isotherms at other temperatures as well as isotherms of mixture of carbon dioxide and methane in activated carbon and carbon nanotube at 273 and 300 K. Good agreement between the computed and experimental isotherm data was observed, thus justifying the use of a simple adsorption model.     

Novel MCM-41 Supported Dicationic Imidazolium Ionic Liquids Catalyzed Greener and Efficient Regioselective Synthesis of 2-Oxazolidinones from Aziridines and Carbon Dioxide

A type of MCM-41 supported dicationic imidazolium ionic liquid nanocatalyst has been synthesized and found to be competent for the synthesis of 2-oxazolidinones through the sustainable chemical conversion of CO₂ with aziridines. It was shown that the highest efficiency was achieved in the cycloaddition of a series of aziridines and CO₂ in the presence of a catalytic amount of the solid catalyst MCM-41@ILLaCl₄ under mild conditions. Merits of this meticulously designed protocol are the use of a novel supported ionic liquid catalyst, the easy work-up process, good to excellent yields, a short reaction time, and purification without column chromatography. Overall, the present protocol of synthesizing 2-oxazolidinones under cocatalyst- and solvent-free conditions using MCM-41@ILLaCl₄ is promising for industrial applications.     

CO2 regulates phase transition of sodium oleate and 3-(diethylamino)-propylamine in aqueous solution

We reported that the phase conversion of the micelles in aqueous solution prepared by sodium oleate (NaOA) and 3-(diethylamino)-propylamine (DEAPA) in the presence of carbon dioxide. This micellar structure is very sensitive to CO₂ and the pH value of the solution is continuously reduced with the continuous introduction of carbon dioxide. When pH?>?10.2, the mixed solution of NaOA and DEAPA is mainly in the form of spherical micelles; when the 10.2?>?pH?>?9.6, the mixed solution mainly in the worm-like micelles (WLM), where the solution has a significant viscosity change; when the 9.6?>?pH?>?9.1, the NaOA and DEAPA mixed solution becomes the aqueous two-phase system (ATPS), which is composed of two layers, the upper layer is the vesicle structure and the lower layer is the WLM structure; when the pH between 9.1?>?pH?>?9.0, NaOA and DEAPA mixed solution form vesicles, thus realizing the regulation of CO₂ on the micellar structure transition of NaOA and DEAPA mixed solution. Such these microstructures transition could be confirmed by Rheology measurement, DLS and Cryo-TEM.     

Physical and Excess Properties for Binary Mixtures of 1-Methyl-3-Octylimidazolium Tetrafluoroborate, [Omim][BF4], Ionic Liquid with Different Alcohols

In recent years, ionic liquids have increasingly gained importance as green solvents. The potential of these organic salts, which are moisture and air stable at room temperature, for new chemical processes and technologies is beginning to be recognized. Research on the thermophysical properties of ionic liquids and their mixtures form the basis for future applications. In this contribution, densities, refractive indices, speeds of sound and dynamic viscosities of 1-methyl-3-octylimidazolium tetrafluoroborate, [Omim][BF₄], the room temperature ionic liquid (IL) in binary mixtures with methanol, ethanol, 1-propanol and 2-propanol were measured at 298.15K and atmospheric pressure. The excess molar volumes and molar refraction, isentropic compressibility and dynamic viscosity changes of mixing have been calculated and were satisfactorily correlated by the Redlich–Kister polynomial.     

Effects of CO2 Injection on Phase Behavior of Crude Oil

CO₂ flooding is a win-win technology, sequestrating greenhouse CO₂ while producing a significant amount of crude oil to help defray the cost of CO₂ sequestrating and enhancing oil recovery. However, due to the difference of sedimentary environment and poor properties of formations, physical properties of the crude oil and the effect of CO₂ flooding are not always satisfactory in most oilfields of China. Therefore, in this article, to improve the understanding of the oil recovery mechanisms and feasibility of CO₂ flooding in China, based on the oil and gas of Mao-3 oilfields, phase behavior of the CO₂ and crude oil system was investigated. Parameters like saturated pressure, volume factor, gas oil ratio, and viscosity were measured and their relationships analyzed. Results show that crude oil of Mao-3 reservoir and CO₂ has good mutual dissolution under reservoir conditions, and CO₂ could expand the oil and reduce the oil viscosity greatly. As a result, formation energy could be enhanced and flow characteristics of the oil could be improved by CO₂ flooding.     

Experimental Research on NO2 Viscosity and Absorption for (1-Ethyl-3-methylimidazolium Trifluoroacetate + Triethanolamine) Binary Mixtures

The viscosity (9.34–405.92 mPa·s) and absorption capacity (0.4394–1.0562 g·g⁻¹) of (1-ethyl-3-methylidazolium trifluoroacetate + triethanolamine) binary blends atmospheric pressure in the temperature range of 303.15–343.15 K and at different mole fractions of [EMIM] [TFA] have been carried out. The molar fraction of [EMIM] [TFA] dependence of the viscosity and absorption capacity was demonstrated. The addition of a small amount of [EMIM] [TFA] into TEA led to rapidly decreased rates of binary blends’ viscosity and absorption capacity. However, the viscosity and absorption of binary blends did not decrease significantly when [EMIM] [TFA] was increased to a specific value. Compared with the molar fraction of the solution, the temperature had no obvious effect on viscosity and absorption capacity. By modeling and optimizing the ratio of viscosity and absorption capacity of ([EMIM] [TFA] + TEA), it is proven that when the mole fraction of [EMIM] [TFA] is 0.58, ([EMIM] [TFA] + TEA) has the best viscosity and absorption capacity at the same time. In addition, at 303.15 K, ([EMIM] [TFA] + TEA) was absorbed and desorbed six times, the absorption slightly decreased, and the desorption increased.     

Changes in Porous Parameters of the Ion Exchanged X Zeolite and Their Effect on CO2 Adsorption

Zeolite 13X (NaX) was modified through ion-exchange with alkali and alkaline earth metal cations. The degree of ion exchange was thoroughly characterized with ICP, EDS and XRF methods. The new method of EDS data evaluation for zeolites was presented. It delivers the same reliable results as more complicated, expensive, time consuming and hazardous ICP approach. The highest adsorption capacities at 273 K and 0.95 bar were achieved for materials containing the alkali metals in the following order K < Na < Li, respectively, 4.54, 5.55 and 5.94 mmol/g. It was found that it is associated with the porous parameters of the ion-exchanged samples. The Li_0.61Na_0.39X form of zeolite exhibited the highest specific surface area of 624 m²/g and micropore volume of 0.35 cm³/g compared to sodium form 569 m²/g and 0.30 cm³/g, respectively. The increase of CO₂ uptake is not related with deterioration of CO₂ selectivity. At room temperature, the CO₂ vs. N₂ selectivity remains at a very high stable level prior and after ion exchange in co-adsorption process (X_CO2 during adsorption 0.15; X_CO2 during desorption 0.95) within measurement uncertainty. Additionally, the Li_0.61Na_0.39X sample was proven to be stable in the aging adsorption-desorption tests (200 sorption-desorption cycles; circa 11 days of continuous process) exhibiting the CO₂ uptake decrease of about 6%. The exchange with alkaline earth metals (Mg, Ca) led to a significant decrease of SSA and micropore volume which correlated with lower CO₂ adsorption capacities. Interestingly, the divalent cations cause formation of mesopores, due to the relaxation of lattice strains.     

The Crystal Structures, Microstructure and Ionic Conductivity of Ba2In2O5 and Ba(InxZr1−x)O3−x/2

This paper describes the results of electron microscopy, high-temperature powder neutron diffraction, and impedance spectroscopy studies of brownmillerite-structured Ba₂In₂O₅ and perovskite structured Ba(In_xZr_1−x)O_3−x/2. The ambient temperature structure of Ba₂In₂O₅ is found to adopt Icmm symmetry, with disorder of the tetrahedrally coordinated (In³⁺) ions of the type observed previously in Sr₂Fe₂O₅. Ba₂In₂O₅ undergoes a ∼6-fold increase in its ionic conductivity over the narrow temperature range from ∼1140 K to ∼1230 K, in broad agreement with previous studies. This transition corresponds to a change from the brownmillerite structure to a cubic perovskite arrangement with disordered anions. Electron microscopy investigations showed the presence of extended defects in all the crystals analyzed. Ba(In_xZr_1−x)O_3−x/2 samples with x=0.1 to 0.9 adopt the cubic perovskite structure, with the lattice parameter increasing with x.     

Influence of the Cation on the Solubility of CO<Subscript>2</Subscript> and H<Subscript>2</Subscript> in Ionic Liquids Based on the Bis(trifluoromethylsulfonyl)imide Anion

Experimental values for the solubility of carbon dioxide and hydrogen in three room temperature ionic liquids based on the same anion—(bistrifluoromethylsulfonyl)imide [Ntf₂]—and three different cations—1-butyl-3-methylimidazolium, [C₄mim], 1-ethyl-3-methylimidazolium, [C₂mim] and trimethyl-butylammonium, [N₄₁₁₁]—are reported between 283 and 343 K and close to atmospheric pressure. Carbon dioxide, with a mole-fraction solubility of the order of 10⁻², is two orders of magnitude more soluble than hydrogen. The solubility of CO₂ is very similar in the three ionic liquids although slightly lower in the presence of the [C₂mim] cation. In the case of H₂, noticeable differences were observed with larger mole fraction solubilities in the presence of [N₄₁₁₁] followed by [C₄mim]. All of the mole-fraction solubilities decrease with increasing temperature. From the variation of Henry’s law constants with temperature, the thermodynamic functions of solvation were calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry’s law constants from appropriate smoothing equations, is always better than ±1%.     

Resonant Ionic,Covalent Bond,and Steric Characteristics Present in 1Σu+ States of Li2

The molecular bonding in the excited states of the alkali dimers involves the resonant ionic, covalent bond and steric interactions. We show here the case of the ¹Σ_u⁺ states of Li₂ by ab initio calculation. These interactions as functions of the internuclear distance lead to complex potential energy curves, providing an important application for high resolution laser spectroscopy. The spectroscopic constants for the 4 and 5 ¹Σ_u⁺ states are obtained for the first time.     

Effect of composition changes on properties and defect structure of crystalline Sm-doped ZrO<Subscript>2</Subscript>

Polymorphous structure, electrical conductivity, absorption coefficient, refractive index, and mechanical characteristics of crystalline system ZrO₂ + x Sm₂O₃ (x = 4–43 mol %) is investigated. Vickers microhardness is investigated by the well-known quasi-static indentation method. Plastic microhardness and the effective elastic modulus are studied by the depth-sensing indentation technique. Special attention is devoted to the ordered defect fluorite structure, pyrochlore phase Sm₂Zr₂O₇, observed for x = 43 mol %. Potential applications of the investigated system are discussed. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 4, pp. 402–411. The text was submitted by the authors in English.