An ab initio study of ionic liquid silver complexes as carriers in facilitated olefin transport membranes

Liquid phase isoprene/n-pentane mixtures can be separated through the use of facilitated transport membranes containing complexes of silver ions with an ionic liquid (IL). 1-Butyl-3-methyl imidazolium tetrafluoroborate and zwitterion-type imidazolium compounds containing covalently-bound sulfonate groups form complexes with AgX (X = BF₄, NO₃, and ClO₄). Facilitated isoprene transport has been observed with selectivities that depend on the counteranion of the silver salt. The facilitated transport phenomena of the olefin and IL/silver complexes were investigated theoretically by calculating their complexation energies (i.e., the energy of formation of the silver complexes with the olefin) with the density functional theory method. Among polymer/silver salt systems, the polymer/AgBF₄ system has been found to be generally more favorable for facilitated olefin transport than the polymer/AgNO₃ system because of the low lattice energy of AgBF₄. However, there is a different trend for IL/AgX systems. This difference may arise because the positively charged components of the IL can interact with the anions of the silver salt, which changes the olefin complexation activity. For IL/AgX systems, the selectivity varies inversely with the complexation energy, which implies that the diffusion of the carrier may be the significant factor affecting isoprene/n-pentane separation, once the appropriate complexation has occurred between olefin molecules and the ILsilver complexes.     

Nanocomposite membranes containing positively polarized gold nanoparticles for facilitated olefin transport

Positively polarized gold nanoparticles have been demonstrated for use as stable olefin carriers for facilitated olefin transport membranes. The formation and size of gold nanoparticles stabilized by 4-dimethylaminopyridine (DMAP) were monitored using X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–visible spectroscopy. Nanocomposite membranes that deliver high separation performance for olefin/paraffin mixtures were prepared by dispersing gold nanoparticles stabilized by DMAP in a polymer matrix, poly(vinyl pyrrolidone) (PVP). X-ray photoelectron spectroscopy (XPS) and zeta potential measurements revealed that gold nanoparticles stabilized by DMAP exhibited a high positive polarity, which is responsible for the reversible interaction between the gold nanoparticles and olefin molecules. Compared to neat PVP membranes, the composite membranes consisting of PVP and the polarized gold nanoparticles showed stable and enhanced separation of olefin/paraffin mixtures.     

Impact of ionic liquids on silver thermoplastic polyurethane composite membranes for propane/propylene separation

This work describes newly synthesized composite polymeric membranes and their utilization in propane/propylene separation in a gas mixture. The nonporous composite polymers were successfully synthesized by using thermoplastic polyurethane (TPU) and several silver salts/silver salts with ionic liquids (ILs). Our studies showed that silver bis(trifluoromethanesulfonyl)imide (Ag[Tf₂N]) containing membranes outperformed other silver salt containing membranes in terms of selectivity. In addition, to this finding, ILs, as additives for the membranes, enhanced the selectivity by facilitating improved coordination of the olefin with the silver ions in the dense composite polymers.     

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.     

Partially positively charged silver nanoparticles prepared by p-benzoquinone

Partially positively charged silver nanoparticles were successfully prepared by interaction between p-benzoquinone and the surface of the nanoparticles. This result was primarily due to electron affinity of the carbonyl group in p-benzoquinone, as confirmed by FT-IR and X-ray photoelectron spectroscopy (XPS). In this study, p-benzoquinone acted as both a stabilizer and a reducing agent for silver nanoparticles. UV–vis spectra showed the formation of silver nanoparticles. TEM micrographs confirmed that most of silver nanoparticles exist in sizes less than 7 nm, and the average size of particle aggregates is approximately 20 nm.     

Mathematical modeling of silver extraction by an emulsion liquid membrane process

A general physical model of a typical batch extraction system employing an emulsion liquid membrane process for the extraction of silver has been developed. The model takes into account the extraction reaction between the silver ion and the carrier molecules at the external interface, the diffusion of the complex in the membrane phase, the stripping reaction at the internal interface and the reaction of silver ion with the reagent, HCL, in the internal phase to yield silver chloride incapable of permeating through the membrane phase. In addition, the leakage of the internal aqueous phase to the external aqueous phase due to membrane breakage has been incorporated in this model. The batch extraction of silver using D2EHPA as a carrier has been carried out under various experimental conditions. The experimental data can be well explained by the present model.     

Role of anions for the reduction behavior of silver ions in polymer/silver salt complex membranes

The reduction of silver ions to silver nanoparticles is an essential issue in polymer/silver salt complex membranes for facilitated olefin transport, because it has a critical influence on the long-term stability of membrane performance. In this study, the role of anions for the formation of silver nanoparticles in polymer/silver salt complexes was investigated. This role was assessed for the complexes of poly(N-vinyl pyrrolidone) (PVP) with three silver salts including AgBF₄, AgCF₃SO₃, and AgNO₃. Especially, UV irradiation to the membranes was used to clearly investigate the reduction behavior of silver ions. Separation performance test, UV–vis spectroscopy and transmission electron microscopy (TEM) clearly show that the reduction rate of silver ions strongly depends on the counteranions of salt, and has the following order: AgBF₄ > AgCF₃SO₃ > AgNO₃. This behavior of the formation of silver nanoparticles in polymer/silver salt complex membranes is explained in terms of the interaction strength of silver ions with the carbonyl oxygens of polymer, and that of silver ions with counteranions. It is concluded that when the former interaction is strong and the latter one is weak, the reduction rate of silver ions to silver nanoparticles is fast, and vice versa. These interactions were characterized using FT-IR, FT-Raman spectroscopy, and theoretical ab initio calculation.     

Sorbent coatings for solid-phase microextraction based on mixtures of polymeric ionic liquids

Four polymeric ionic liquids based on two different cations, poly(1‐vinyl‐3‐hexylimidazolium) and poly(1‐vinyl‐3‐hexadecylimidazolium), combined with two different anions, bis[(trifluoromethyl)sulfonyl]imide (NTf) and chloride (Cl^?), were combined in various weight percentages and used as sorbent coatings for solid‐phase microextraction gas chromatography (SPME‐GC). The selectivity of the fiber coatings for 12 test analytes was examined. The extraction efficiency of n‐alcohols increased with an increase in the weight percentage of chloride ion in the sorbent coating. The ability to tune the interactions between the coating material and the analytes was exploited and resulted in distinct changes in the limits of detection for hydrogen‐bonding analytes with varying chloride ion content in the sorbent coating.     

Effect of carrier concentration on the facilitated oxygen transport in a polymer membrane

Facilitated transport of oxygen in a solid Polymer membrane containing cobaltporphyrin (CoP) which carries oxygen specifically and reversibly, leads to permselectivity of oxygen against nitrogen in the membrane. The increase in concentration of the CoP carrier is expected to enhance the oxygen transport. The membranes of poly(octylmethacrylate-co-vinylimidazole) containing 0.8 ～ 10 wt% CoP were prepared, and the effects of the CoP-concentration on the transport and the diffusion constants of oxygen are studied. Although the induction period before the steady state of oxygen permeation was prolonged with the CoP concentration in the polymer membrane, the glass transition temperature (T_g) of the membrane was increased and the diffusion constants of oxygen were decreased with the CoP concentration to yield unexpected reduction of the oxygen permeation in the highly CoP loaded membrane.     

环境友好型离子液体催化环氧丙烷反应合成丙二醇醚

丙二醇醚类化合物是性能优良的精细化学品,也是环保型高级溶剂.该类化合物具有两个强溶解性功能基团—醚键和羟基,前者具有亲油性,可溶解疏水性物质,后者具有亲水性,可溶解亲水性物质,因而丙二醇醚具有很强的溶解能力,素有"万能溶剂"之称,可广泛应用于涂料、油墨、油漆、印刷、电子化学品、染料、净洗和纺织等行业.丙二醇醚类化合物目前主要由环氧丙烷和低级脂肪醇反应合成,然而,由于环氧丙烷的位阻效应,使其在酸或碱的条件下开环的位置会不同,从而得到不同的醇醚产物.由于碱催化的醇醚产物更加环境友好,因而越来越被人们所关注.工业上丙二醇醚合成多采用传统的强碱性催化剂醇钠以及氢氧化钠,腐蚀性强,产生的废液量大.本文采用环境友好的非卤素离子液体作为催化剂,研究了其催化环氧丙烷醚化合成丙二醇醚的反应特性.本文采用两步法合成了一系列环境友好的醋酸类碱性功能化离子液体,并在温和的条件下将其用于催化环氧丙烷与醇反应合成丙二醇醚.结果表明,该类离子液体可以高效催化该反应的进行.利用紫外-可见光谱测定Hammett指数来表征实验中所用离子液体的碱强度,并构建了离子液体碱性与催化活性之间的关系.结果表明,离子液体的催化性能和其碱性密切相关,随着离子液体碱性的增加,催化活性增强,其中咪唑醋酸类离子液体碱性强于季胺类,表现出优异的催化性能.离子液体的碱性明显弱于NaOH,但却呈现出更优异的催化性能.相同反应条件下,EmimOAc离子液体作为催化剂,PO的转化率分别较NaOH高出20%–30%,选择性略高于NaOH,这可能是由于二者催化机理不同造成的.传统NaOH催化机理的关键步骤是醇在碱性催化剂的作用下去质子化形成电子供体烷氧根离子,促进环氧丙烷的开环加成.而本文提出了离子液体亲电亲核双活化作用机理,即离子液体在阴阳离子之间的氢键和电荷相互作用的共同作用下,促进环氧丙烷开环和醇的去质子化,形成相应的反应中间体.通过电喷雾质谱分析手段检测到了阴阳离子通过协同作用亲电亲核催化过程中的反应中间体,证明了该假设机理的可行性.此外,还考察了催化剂浓度、醇比、反应温度以及醇的空间位阻效应对反应的影响.以EmimOAc催化合成丙二醇丁醚为例,反应的转化率随催化剂浓度的增加而增大,在催化剂添加量1%(催化剂与PO的摩尔比)时,PO转化率达到最大值为98.2%,1-丁氧基-2-丙醇的选择性为86.4%.当正丁醇与环氧丙烷的摩尔比为3时,转化率最高为88.6%,选择性高达94%.该反应为放热反应,最适反应温度约为140 oC,此时转化率高达96.5%.在环氧丙烷和不同的低碳醇合成丙二醇醚的反应中,反应物醇的碳链越短,支链越少,催化反应效率越高.     

Three-component coupling of aldehyde, alkyne, and amine catalyzed by silver in ionic liquid

A three-component coupling of aldehyde, alkyne, and amine was developed by using gold, copper, or silver as catalysts in ionic liquid.     

A novel one step synthesis of silver nanoparticles using room temperature ionic liquid and their biocidal activity

This article reports the synthesis of silver Nan particles (SNPs) using 1-(dodecyl) 2 amino-pyridinium bromide ionic liquid. This is a new one phase method for the synthesis of uniform monodispersed crystalline silver nanoparticles in a water-ionic liquid system. In this work, the functionalized room temperature IL acts as stabilizing agent and solvent. Hydrazine hydrate acts as reducing agent. To the best of our knowledge, there is no report of the synthesis of metal nanoparticles using this ionic liquid. The synthesis of silver nanoparticles is very primarily studied by UV-Visible spectroscopic analysis. The TEM and particle size distribution was used to study morphology and size of the particles. The charge on synthesized SNPs was determined by Zeta potential. The silver nanoparticles have been known to have inhibitory and bactericidal effect. The investigation of antibacterial activities of ionic liquid stabilized silver nanoparticles was performed by measurement of the minimum inhibitory concentration.     

Hydrogenation of aryl ketones using palladium nanoparticles on single-walled carbon nanotubes in an ionic liquid

Single-walled carbon nanotubes (SWNTs) are used as supporting materials for palladium (Pd) nanoparticles generated in situ in ionic liquid (IL); Pd nanocatalysts on SWNTs exhibit superior reactivity for hydrogenation of aryl ketones in IL under mild conditions (1 atm of H₂ (g) and room temperature) and can be reused above 10 times without any loss of catalytic activity.     

Influence of ionic liquids on the separation factor of three standard separation problems

Vapor–liquid equilibria (VLE) for the binary systems benzene–cyclohexane, 1-hexene–n-hexane and 2-propanol–water and the ternary systems with the ionic liquids 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [HMIM]⁺[BTI]⁻ and 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [BMPYR]⁺[BTI]⁻ as entrainers were measured, to investigate the influence of ionic liquids on the separation factors. The experimental data were compared with the predicted results using mod. UNIFAC (Do). The predicted results are in good agreement with the experimental data.     

Biosensor for chlorogenic acid based on an ionic liquid containing iridium nanoparticles and polyphenol oxidase

A biosensor based on the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate containing dispersed iridium nanoparticles (Ir-BMI.PF₆) and polyphenol oxidase was constructed. This enzyme was obtained from the sugar apple (Annona squamosa), immobilized in chitosan ionically crosslinked with oxalate. The biosensor was used for determination of chlorogenic acid by square wave voltammetry. The polyphenol oxidase catalyzes the oxidation of chlorogenic acid to the corresponding o-quinone, which is electrochemically reduced back to this substance at +0.25 V vs. Ag/AgCl. Under optimized operational conditions the chlorogenic acid concentration was linear in the range of 3.48 × 10⁻⁶ to 4.95 × 10⁻⁵ mol L⁻¹ with a detection limit of 9.15 × 10⁻⁷ mol L⁻¹. The biosensor was applied in the determination of chlorogenic acid in organic and decaffeinated coffee and the results compared with those obtained using the capillary electrophoresis method. The recovery study for chlorogenic acid in these samples gave values of 93.2-105.7%.     

Application of 1-alkyl-3-methylimidazolium-based ionic liquids in separation of bioactive flavonoids by capillary zone electrophoresis

Room-temperature ionic liquids (ILs) are liquids that are constituted entirely of ions and can provide a solvent environment quite unlike any other available at room temperature. They continue to attract considerable interest in the chemistry research community as they are good solvents for a wide range of both inorganic and organic materials. In this study, a CZE method has been established for resolving natural flavonoids, quercetin, kaempferol and isorhamnetin in the Chinese herbal extract from Hippophae rhamnoides and its medicinal preparation (Sindacon Tablet). In this method, 1-alkyl-3-methyl-imidazolium-based ILs are used as the additive, and the effects of the alkyl group, imidazolium counterion (anionic part), along with the concentration of IL are investigated and discussed. Baseline separation, high efficiencies and symmetrical peaks of the three flavonoids were obtained. The separation mechanism seems to be the hydrogen-bonding interaction between the imidazolium cations of IL and the flavonoids.     

CO2/H2 separation by facilitated transport membranes immobilized with aqueous single and mixed amine solutions: Experimental and modeling study

An experimental and theoretical analysis to separate CO₂ using facilitated transport membranes immobilized with different aqueous single and mixed amine solutions have been performed. The membranes containing monoethanolamine (MEA), diethanolamine (DEA), monoprotonated ethylenediamine (EDAH⁺) and piperazine (PZ), as well as aqueous blends of PZ with MEA, DEA or EDAH⁺ were considered. The aqueous solution of PZ showed the highest CO₂ permeation rate with respect to other single amine solutions. Therefore blends of PZ with MEA, DEA and EDAH⁺ increased the permeance of carbon dioxide through mixed amine membranes.     

Electron beam induced in-vacuo Ag deposition on TiO2 from ionic liquids

The present work describes electron beam induced Ag deposition from [BMIM][BF₄] ionic liquid containing AgBF₄ on anatase TiO₂ surfaces. The procedure is directly performed in the ultra high vacuum chamber of a scanning electron microscope (SEM). Based on the experiments with reference surfaces (Au and amorphous TiO₂) that do not show successful Ag deposition, it is proposed that the deposition mechanism is of pseudo-photocatalytic nature.     

Effect of the polymer matrix on the formation of silver nanoparticles in polymer–silver salt complex membranes

When polymer–silver salt complex membranes were exposed to UV irradiation, the separation performances of both the permeance and selectivity for propylene–propane decreased, which was primarily attributed to the reduction of the silver ions in the membranes to silver nanoparticles. Here, the effect of the polymer matrix on the formation of silver nanoparticles in the polymer–silver salt complex membranes was investigated. This effect was assessed for the complexes of two kinds of silver salts (AgBF₄ and AgCF₃SO₃) with several polymeric ligands containing three different carbonyl groups, including poly(vinyl pyrrolidone) (PVP) with an amide group, poly(vinyl methyl ketone) (PVMK) with a ketone group, and poly(methyl methacrylate) (PMMA) with an ester group. UV–vis spectra and transmission electron microscopy (TEM) images clearly indicated that the reduction rate of the silver ions has the following order in the various polymer matrices: PVP > PVMK > PMMA, whereas the size and the distribution of the nanoparticles exhibited the reverse order. The tendency to form silver nanoparticles was explained in terms of the differences between the comparative strengths of the interactions of the silver ions with the different carbonyl oxygens in the matrices, as well as that of the silver ions with counteranions, which was characterized by X‐ray photoelectron spectroscopy (XPS) and FT‐Raman spectroscopy. It was concluded that when the concentration of free silver ions was low due to weak polymer–silver ion and strong silver ion–anion interactions, as found with PMMA, the reduction rate of silver ions to silver nanoparticles was slow. Therefore, the PMMA–silver complex membranes were less sensitive to decreases in separation performance upon UV irradiation than compared to the PVP membranes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1168–1178, 2006