Desulfurization using the 1,2-dimethylimidazolium ionic liquid as an adsorbent

The aim of this study is to investigate the possible use of a 1,2-dimethylimidazolium ionic liquid,2,2-bis((1,2-dimethylimidazolium)methyl)propane-1,3-diol hexafluorophosphate(1),as an adsorbent to selectively remove aromatic heterocyclic sulfur compounds from model fuels.The result indicates that adsorbent 1 is insoluble in model fuels.The spent IL saturated sulfur compounds could be regenerated by a water dilution process.The influence of extraction time or temperature as well as the molar ratio of 1 to aromatic heterocyclic sulfur compound was also studied.     

Modeling of an ionic liquid electrospray using molecular dynamics with constraints

Molecular dynamics simulations have been performed to investigate the behavior of the EMIM-BF(4) ionic liquid for conditions similar to those of electrospray thrusters. To study the physics of ion extrusion a large system composed of approximately 2160 ion pairs was placed inside a platinum capillary and equilibrated. Diffusion coefficients and electrical conductivity were calculated and compared with literature values, showing good agreement and validating the use of a constrained dynamics model with a coarse-grained potential. An electric field was applied to the system in the longitudinal direction and the fraction of solvated and non-solvated emitted ions was analyzed. The threshold electric field for particle emission was found to be 1.2 V/nm, consistent with other reported work.     

Gravimetric determination of molybdenum and tungsten using pyridoin as a reagent

Summary Pyridoin has been used as a reagent for the gravimetric determination of molybdenum and tungsten. The reagent quantitatively precipitates molybdenum from ammonium molybdate solution at p_H 2.0–9.5 and tungsten from sodium tungstate solution at p_H 2.0–4.5. The precipitate in each case is ignited to the oxide and weighed.

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Zusammenfassung Zur gravimetrischen Bestimmung von Molybdän und Wolfram wird Pyridoin als Reagens empfohlen. Molybdän wurde aus Ammoniummolybdatlösung bei p_H 2,0–9,5 quantitativ ausgefällt, Wolfram aus Natriumwolframatlösung bei p_H 2,0–4,5. Die Niederschläge wurden jeweils zum Oxid verglüht und dieses ausgewogen.

     

新型离子液体作为溶剂萃取光度法测定环境水中超痕量钼

离子液体是一种绿色溶剂,可替代易挥发的有机溶剂用于液/液萃取。在阳离子表面活性剂CTMAB存在下,Mo(Ⅵ)与9-(2-羟基-5-偶氮对甲苯)苯基荧光酮(MBASF)反应形成稳定的络合物,其最大吸收波长位于522 nm。在显色后的体系中加入离子液体-1-丁基-3-三甲基硅咪唑六氟磷酸盐([C4tmsim][PF6]),Mo-MBASF络合物被高效萃取进入离子液体相。由于离子液体在萃取前后均为透明液体,可直接用于光度法测定钼。在1000 mL水样中,0~4μg Mo(Ⅵ)符合比尔定律,络合物的表观摩尔吸光系数达1.2×107L.mol-1.cm-1。绝大多数离子可大量存在,方法具有高的灵敏度和选择性,已应用于环境水样中超痕量钼的测定。     

One-pot synthesis of quinoxaline-2-carboxylate derivatives using ionic liquid as reusable reaction media

The catalyst-free one-pot synthesis of quinoxaline-2-carboxylate is reported by the reaction of α-halo-β-ketoesters with 1,2-diamines using an ionic liquid as an environmentally benign solvent. The recovered ionic liquid was reused for four to five cycles. Moreover, the method is applicable for a variety of 1,2-diamines and α-halo-β-ketoesters.     

Electrochemical property and analysis application of biosensors in miscible nonaqueous media—Room-temperature ionic liquid

Stable heme proteins entrapped in dimethylformamide (DMF)–chitosan organohydrogel films modified electrodes were operated in neat hydrophilic room-temperature ionic liquid (IL) [bmim][BF₄] for the first time. The modified electrodes possess outstanding electrochemical response in [bmim][BF₄] without adding water. The morphology studies of films were demonstrated by atomic force microscopy (AFM). UV–Vis and FTIR spectroscopy showed that the heme proteins retained their native structure in organohydrogel films. Direct electrochemistry and bioelectrocatalysis of heme protein–organohydrogel films were investigated. Several electrochemical parameters such as the charge transfer coefficients (α) and the apparent electron transfer rate constant (k_s) of these processes were calculated by performing nonlinear regression analysis of square wave voltammetry (SWV) experimental dates. Furthermore, high electrocatalytic activity to hydrogen peroxide (H₂O₂) was observed, indicating that heme proteins entrapped in organohydrogel films retained their bioelectrocatalytic activities in [bmim][BF₄]. Kinetic analysis of the cyclic voltammetry dates shows that heme protein–organohydrogel films operated in IL bring up to an enhancement of the biosensor sensitivity and a high affinity for H₂O_2.     

Electrochemical synthesis of gallium nanowires and macroporous structures in an ionic liquid

The electrochemical synthesis of gallium nanostructures in an ionic liquid is presented. Gallium nanowires and macroporous structures were synthesized by the template-assisted electrodeposition in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]TFSA) containing GaCl(3) as the precursor. Track-etched polycarbonate membranes with an average pore diameter of 90 nm and a thickness of 21 μm were used as templates for the nanowire synthesis. Ga nanowires with a length of more than 4 μm and an average diameter corresponding to that of the template's pores were easily obtained by this method. Macroporous structures with an average pore diameter of 600 nm were obtained by the electrochemical deposition of Ga inside polystyrene colloidal crystal templates and the subsequent removal of the template by THF. The macroporous deposit showed a granular morphology with smallest grain sizes of about 40 nm and light reflections. The nanostructures of Ga were characterized by HR-SEM and EDX analysis.     

用聚合表面活性剂作增敏试剂分光光度测定钼和钨

采用表面活性剂的分光光度分析法应用日趋广泛。这方面的研究工作虽极活跃,但较多工作限于已有经典表面活性剂的研究与应用,为分析化学的特定需要设计与合成新型表面活性剂的研究尚少。作者曾用环氧氯丙烷和长链烷基叔胺合成了以聚乙二醇为主链含有若干个带长链烷基的季氮支链的低聚合表面活性剂——聚(氧化丙烯)-α-十八烷基二甲基氯化铵(PPOSA)。实验表明,这类表面活性剂兼有阳离子和非离子表面活性剂的某些特性。本文     

Electrochemical synthesis and the functionalization of few layer graphene in ionic liquid and redox ionic liquid

Electrochemical reductive exfoliation of graphite to few layered graphene(FLG) in presence of 1-ethyl-2,3-dimethyl imidazolium bis(trifluoromethylsulfonyl) imide ionic liquid and redox ionic liquid based ferrocene has been investigated. Thus, by applying a mild negative potential(-2.7 V vs. Fc/Fc~+) to carbon electrode in ionic liquid graphene flakes could be generated. The generated materials have been characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, high resolution transmission electron microscopy and atomic force microscopy. XPS and Raman analysis show that the electrochemical reductive exfoliation provides the formation of FLG. The thickness of the resulting FLG was found to be ranged between 4 and1 nm. HR-TEM images reveal the formation of few graphene layers and in some cases single graphene layer was observed.Moreover, this electrochemical route conduces to the formation of ionic liquid functionalized FLG. Finally, the reductive exfoliation was further investigated in the presence of redox ionic liquid. XPS and electrochemical measurements confirm the presence of ferrocene.     

The determination of molybdenum and tungsten in sea and surface water

A simple method for the determination of molybdenum and tungsten in sea and surface water is presented. Molybdenum and tungsten are concentrated on activated charcoal by adsorption as the ammonium pyrrolidine dithiocarbamate complex; the optimal pH for adsorption is 1.3. Mo and W are then determined by thermal neutron activation, forming ⁹⁹Mo (T_{$\text{1}\text{2}$} = 66.7 h) and ¹³⁷W (T_{$\text{1}\text{2}$} = 23.8 h), respectively. The ^99mTc daughter of ⁹⁹Mo is measured as soon as the equilibrium between ^99mTc(T_{$\text{1}\text{2}$}= 6 h) and ⁹⁹Mo is established. The detection limits are 0.05 μg Mo l^-1 and 0.05 μg W l^-1 (or 0.001 μg W l^-1 after a simple chemical separation).     

Comparative study of electron transfer reactions at the ionic liquid/water and organic/water interfaces

The rates of electron transfer (ET) reactions at the water/ionic liquid (IL) interface have been measured for the first time using scanning electrochemical microscopy. The standard bimolecular rate constant of the interfacial ET between ferrocene dissolved in 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and aqueous ferricyanide (0.4 M-1 cm s-1) was found to be approximately 30 times higher than the corresponding rate constant measured at the water/1,2-dichloroethane interface. The driving force dependence of the ET rate was investigated over a wide range of the interfacial potential drop values (>200 mV). The observed Butler-Volmer-type dependence is discussed in terms of the interfacial model. The ET was also probed at the interface between aqueous solution and the mixture of the IL and 1,2-dichloroethane. The mole fractions in this mixture were varied systematically to investigate the transition from the water/organic to the water/IL interface. The observed decrease in the rate constant with increasing mole fraction of 1,2-dichloroethane is in contrast with the previously reported direct correlation between the electrochemical rate constant and the diffusion coefficient of redox species in solution.     

Fluorescence probing of temperature-dependent dynamics and friction in ionic liquid local environments

The solvation dynamics and local orientational friction for a series of four ionic liquids have been probed using coumarin 153 (C153) as a function of temperature. These ionic liquids are comprised of nonaromatic organic cations paired with a common anion, bis(trifluoromethylsulfonyl)imide (NTf(2)-). The specific liquids are as follows: N-methyl-tri-N-butylammonium NTf(2)- (N(1444)+/NTf(2)-), N-hexyl-tri-N-butylammonium NTf(2)- (N(6444)+/NTf(2)-), N-methyl-N-butylpyrrolidinium NTf(2)- (Pyrr(14)+/NTf(2)-), and N-methyl-N-ethoxyethylpyrrolidinium NTf(2)- (Pyrr(1(2O2))+/NTf(2)-). The observed solvation dynamics and fluorescence depolarization dynamics occur over a broad range of time scales that can only be adequately fit by functions including three or more exponential components. Stretched exponential distributions cannot adequately fit our data. The solvation and reorientational dynamics of the C153 probe are studied over a range of temperatures from 278.2 to 353.2 K. For both the solvation dynamics and the probe reorientational dynamics, the observed temperature dependence is well fit by a Vogel-Tammann-Fulcher law. To correlate the observed microscopic dynamics with macroscopic physical properties, temperature-dependent viscosities are also measured. Differential scanning calorimetry is used to study the thermodynamics of the phase transitions from the liquid to supercooled liquid to glassy states. For the two tetraalkylammonium liquids, the observed melting transitions occur near 300 K, so we are able to study the dynamics in a clearly supercooled regime. Very long time scale orientational relaxation time constants dynamics on the order of 100 ns are observed in the C153 fluorescence anisotropy. These are interpreted to arise from long-lived local structures in the environment surrounding the C153 probe.     

Enzymatic kinetic resolution of sec-alcohols using an ionic liquid anhydride as acylating agent

A task-specific ionic liquid bearing an anhydride moiety was synthesized for the first time in good yield (83%) through a carbodiimide-mediated coupling reaction. The enantiomeric separation of a series of sec-alcohols was performed via enzymatic kinetic resolution, employing an ionic anhydride as acylating agent and Candida antarctica Lipase B as a biocatalyst. A fast and efficient recovery of both enantiomers was achieved separately due to the ionic nature of the acyl donor, combined with the possibility of carrying out the enzymatic step in an organic solvent.     

Unique role of water content in enzymatic synthesis of ethyl lactate using ionic liquid as solvent

Enzymatic synthesis of ethyl lactate was studied in organic solvents and in ionic liquids to determine optimal media for the reaction, and to investigate the effect of water content on the ester yield. Experiments proved that Cyphos 202 ionic liquid is the best solvent affording the highest ethyl lactate yields. Furthermore, 20 times less enzyme sufficed to carry out the reaction in this ionic liquid compared to organic solvents; ionic liquid could be applied as solvent. Using water removal, the ester yield decreased since a side reaction, dimerization of lactic acid, occurred as well. In contrast to these results, without water removal, the produced water was partly consumed by the decomposition of lactoyllactic acid to free lactic acid, increasing thus the substrate concentration of the mixture and enhancing the ester yield.     

SECM study of solute partitioning and electron transfer at the ionic liquid/water interface

Molecular partitioning and electron-transfer kinetics have been studied at the ionic liquid/water (IL/water) interface by scanning electrochemical microscopy (SECM). The ionic liquid C8mimC1C1N is immiscible with water and forms a nonpolarizable interface when in contact with it. Partitioning of ferrocene (Fc) across the IL/water interface was studied by SECM and found to be kinetically fast with a partition coefficient CIL/CW of 2400:1. The partition coefficient value was measured by SECM under quasi-steady-state conditions without waiting for complete solute equilibration. To investigate the kinetics of the electron transfer (ET) between aqueous ferricyanide and Fc dissolved in IL, a new approach to the analysis of the SECM current-distance curves was developed to separate the contributions of Fc partitioning and the ET reaction to the tip current. Several combinations of different aqueous and nonaqueous redox species were investigated; however, only the Fc/Fe(CN)63- system behaved according to the Butler-Volmer formalism over the entire accessible potential range.     

二茂铁在离子液体1-甲基-3-丁基咪唑鎓盐中的电化学行为

在电化学领域,由于离子液体有较宽的电化学窗口、高的电导率而吸引着众多的研究者。伏安法常被用于测定离子液体的电化学行为,但一般都是采用金属丝或者不常用的氧化还原物质作参比电极,如I^-／I3^-[8]副和Li^＋／Li^[9],而这些参比并不常用于传统的有机溶剂中,与在传统的有机溶剂中测得的结果不具有可比性,为了克服这个问题,IUPAC推荐的一些电势标准物质作为电势测定标准。本文采用玻碳圆盘电极测定了二茂铁（Fc）在离子液体1-甲基3-丁基咪唑铃盐BMIMBF4中的伏安行为,实验表明,在GC电极上还原过程表现为可逆单电子氧化还原过程,其可逆性良好,可将二茂铁应用于离子液体MBIMBF4中作为准参比系统。     

Simultaneous determination of molybdenum(VI) and tungsten(VI) and its application in elemental analysis of polyoxometalates

Spectrophotometric determination of molybdenum(VI) and tungsten(VI) with application of Artificial Neural Networks is proposed and it was applied for elemental analysis of solid polyoxometalates. Better results in comparison with previously those achieved by previous published method were demonstrated. MALDI-TOF Mass Spectrometry was tested for possible determination of molecular weight of polyoxometalates utilizing different matrices. Phenomena observed during desorption-ionisation processes are discussed. LDI-TOF MS was found to be suitable for the determination of Mo:W ratio in polyoxometalates as a rapid screening method to follow synthetic procedure.