Journal of Ionic Liquids最新文献

Phosphonium-derived ionic liquids have emerged as a powerful class of thermoresponsive materials with sought after Lower Critical Solution Temperature (LCST) phase separation with applications across a broad range of fields. Herein, we report the spectroscopic examination of phosphonium salts bearing the general structure [X][P_444n] wherein systematic structural variations were designed to gain a fundamental understanding behind the impact of alkyl chain length, anion size, and effective nuclear charge on their temperature-dependent phase separation behavior. Using variable temperature ¹H, ³¹P, and ¹⁹F NMR, the bonding changes which drive LCST phase separation for the assembled thermoresponsive ILs were elucidated. For the first time, spectroscopic evidence revealed a delicate balance between the interdependence of alkyl chain length and anion size on phase separation that formed the basis of new LCST design principles.

Ionic liquids have attracted much attention these last years because they have been identified as a new class of media offering interesting opportunities to transfer the traditional chemical processes to new, clean and eco-friendly technologies. But in order for these compounds to achieve their commercial potential, it must be demonstrated that they can be produced in hundreds of kilograms at a time in a benign simple and highly efficient way. However, the main applications in which they are involved require a high dregree of purity. In the context of the circular economy and with the aim of developing a generic, straightforward, economical and eco-friendly method for high-purity piperidinium-based ionic liquids preparation, we investigate here the experimental conditions of determining step of the synthesis i.e. the Menshutkin reaction. This enables use to offer a high-yield and high-quality protocol, that is easy to scale up and that combines sustainability with cost-effectiveness.

A novel, silica-based pyrrolidinium ionic liquid immobilised on copper-citric acid metal-organic framework ([PyrrSi][Cl]@Cu-Cit-MOF), has been synthesised through an easy-to-handle procedure and is characterised by several techniques such as Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powder X-ray diffraction (PXRD), thermal gravimetric (TG), and Brunauer-Emmett-Teller (BET) analyses. The present protocol is scalable and compatible with a wide range of aldehydes, producing imidazole derivatives in excellent yields (82–96 %) in very short reaction times (10–18 min). Moreover, the catalyst could be recovered and recycled simply by filtration and is reusable for up to six consecutive runs without any significant changes in its catalytic activity.

This study introduces the scaled sigma potential of water (${\sigma }_r$), a new metric using the COSMO-RS (Conductor like Screening Model for Real Solvents) framework, as a descriptor of upper and lower critical solution temperature (UCST and LCST) governed phase separation in aqueous ionic liquid (IL) solutions. The maximum and minimum values of ${\sigma }_r$ correspond to the homogenous and phase separated states, at a given composition, for both UCST and LCST cases. Furthermore, the value of ${\sigma }_r$ changes from positive to negative as the temperature increases in LCST exhibiting solutions, while as the temperature increases in UCST exhibiting solutions, the value of ${\sigma }_r$ changes from negative to positive. Therefore, ${\sigma }_r$ provides a less computationally intensive alternate to Gibbs free energy calculations and to the generation of phase diagrams for assessing UCST/LCST behavior in aqueous IL solutions.

We first report a novel solvent, base free synthesis of carbonyl compound catalyst by FeCl₃/TEMPO at 40 °C with high-rate. In this article, we examine the mechanism of this catalytic system and compare the reactivity of aromatic alcohols. Furthermore, the efficacy of 3-(2-aminoethyl)-1-methyl-1H-imidazol-3-ium bromide [Aemim]Br could be maintained after seven recycling cycles. High catalyst productivity and reaction rate (5.53 to 22.50) have been accomplished with the use of an enhanced procedure.

This paper explores the effect of adding supercritical carbon dioxide (scCO₂) to Ionic Liquids (ILs) for the microextraction of very diluted pollutants from aqueous matrices. The proposed system uses an IL, trihexyl-tetradecyl-phosphonium bis(trifluoromethylsulfonyl)imide ([P_6,6,6,14][Tf₂N]) and 1-hexyl-3-methyl-imidazolium tris(pentafluoroethyl)trifluorophosphate ([hmim][FAP]), as extractant, and scCO₂ as diluent that may change the solvent capacity by changing the solvent polarity. The study was first carried out for the extraction of 3,3′,4,4′-tetrachlorobiphenyl (PCB-77) from aqueous solutions using a designed microextraction cell. Different ILs, sample volumes and kinetics of extraction were investigated. Results show that within 15 min the maximum extraction percentage was achieved employing a scCO₂ partial pressure of 80 bar. To investigate the influence of the polarity change by the presence of carbon dioxide more broadly, other pollutants with different water solubilities were used. It was observed that scCO₂ (partial pressure) reduced the recoveries for benzophenone and PCB-77 but increased the extraction of triclosan. This is due to the change on solvent's polarity and viscosity of the mixture. This was corroborated through a ternary system simulation including IL-pollutant-scCO₂. All these results establish that the combination of CO₂ and IL can in some cases enhance the extraction, but the affinity between the pollutant and scCO₂ is a key parameter that discerns whether expanding the IL with scCO₂ is beneficial for the extraction.

The sulfur compounds in diesel fuel produce harmful environmental pollutants during combustion. Hydrodesulfurization (HDS) is the most common technique to reduce the sulfur content of diesel fuel but cannot effectively remove aromatic sulfur compounds to produce ultra-low-sulfur diesel. Ionic liquids (ILs) show potential as alternative solvents for extractive desulfurization to be implemented after a conventional HDS process, but the mechanism is not well understood. This work focuses on using a combination of molecular simulation free energy calculations and detailed structural analysis to better understand the molecular-level interactions between dibenzothiophene and seven common imidazolium-based ILs. The free energy calculations suggest that the ILs interact differently with thiophene and dibenzothiophene. No specific interactions were observed between the anion and dibenzothiophene; varying the anion showed no remarkable differences in the observed interactions. It was determined that interactions between dibenzothiophene and the cation were more significant; π-π stacking between the imidazole ring and thiophene ring plus favorable electrostatic interactions between the alkyl chain and benzene rings were observed. The primary goal of this work is to use molecular simulations to complement current experimental research to identify suitable ILs for potential extractive desulfurization applications.