Dialkylphosphate Ionic Liquids Research Articles

Tris(dialkylamino)cyclopropenium dialkylphosphate ionic liquids as lubricants.

Six new tris(dialkylamino)cyclopropenium dialkylphosphate ionic liquids (ILs), [C3(NR2)3]BEHP (NR2 = NEt2, NBuMe, NPr2, NBu2, NHex2, NDec2; BEHP = bis(2-ethylhexyl)phosphate), were prepared and characterised as potential lubricants. Thermophysical and thermochemical properties of these ILs were investigated, namely: viscosity, density, conductivity, miscibility, thermal stability and phase transitions. Miscibility studies indicated that [C3(NEt2)3]BEHP would not be suitable due to its water solubility and hexane immiscibility. [C3(NDec2)3]BEHP was not investigated as a lubricant due to its low purity (the chloride salt of this cation is also hexane miscible). Of the other four, [C3(NHex2)3]BEHP was found to exhibit significantly less wear for pin-on-disk test conditions than the standard phosphonium [P6,6,6,14]BEHP IL. The amount of wear was found to generally decrease with increasing molecular weight.

Surface Tension Measurements for Seven Imidazolium-Based Dialkylphosphate Ionic Liquids and Their Binary Mixtures with Water (Methanol or Ethanol) at 298.15 K and 1 atm

Surface tension data were measured by the Wilhelmy plate method for the binary mixtures containing an ionic liquid of the imidazolium dialkylphosphate family and water (methanol or ethanol) at 298.15 K and atmospheric pressure. The enthalpy of vaporization Δ1gHmo and Hildebrand solubility parameter δH for the pure components are estimated from the experimental data, and a perfect correlation is found between surface tension and specific cohesive energy per unit surface area for the imidazolium dialkylphosphate series ionic liquids (ILs). The surface tension as well as the surface tension deviation against the solution composition shows a remarkable difference between the mixtures of an IL with water and with alcohols, which is interpreted qualitatively by the δH values of the corresponding pure components. Some ILs act as a surfactant in aqueous solution, but most of them more like a conventional nonelectrolyte component in the alcoholic solutions.

A convenient two-step synthesis of dialkylphosphate ionic liquids

Dialkylphosphate ionic liquids are useful solvents for cellulose dissolution and catalytic reactions. In this paper, a new methodology for the synthesis of hydrophobic phosphate-based ionic liquids is described. This method involves the oxidation reaction of an easily prepared H-phosphonate precursor by using the environmentally friendly and inexpensive oxidizing agent hydrogen peroxide.

Structure and Thermal Stability of Sugarcane Bagasse Cellulose Regenerated from Dialkylphosphate Ionic Liquids<sup></sup>

A phosphate-based ionic liquid, 1-ethyl-3-methylimidazolium diethylphosphate ([EMI[DE), was synthesized and used to dissolve sugarcane bagasse cellulose under microwave radiation. The original and regenerated cellulose were both characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results showed that cellulose had a more porous and less crystalline structure after regeneration, whereas chemical composition had no change. Thermal stability of the regenerated cellulose was somewhat lower, corresponding to the decreased crystallinity. In short, the treatment with [EMI[DE led to desirable structural modification on sugarcane bagasse cellulose via physical process. This is of great benefit to the subsequent downstream processes, such as enzymatic hydrolysis and ethanol fermentation.

Liquid–liquid extraction of neodymium(iii) by dialkylphosphate ionic liquids from acidic medium: the importance of the ionic liquid cation

The ionic liquids 1-hexyl-3-methylimidazolium bis(2-ethylhexyl)phosphate, [C6mim][DEHP], 1-hexyl-1-methylpyrrolidinium bis(2-ethylhexyl)phosphate, [C6mpyr][DEHP], and tetrabutylammonium bis(2-ethylhexyl)phosphate, [N4444][DEHP], were prepared and characterized using (1)H and (13)C NMR spectroscopy. The extraction behavior of neodymium(iii) from nitrate medium by these ionic liquids, diluted with the room temperature ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C6mim][NTf2], 1-hexyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C6mpyr][NTf2], and tributylmethylammonium bis(trifluoromethylsulfonyl)imide, [N1444][NTf2], was studied. The distribution ratio of neodymium(iii) was measured as a function of various parameters, such as pH, concentration of the ionic liquid extractant, nature of diluents, concentration of ionic liquid cations and nitrate anions in the aqueous phase. The extraction behavior was compared with that obtained for a solution of the molecular extractant bis(2-ethylhexyl)phosphoric acid (DEHPA) in an ionic liquid diluent. The extraction of neodymium(iii) in the ionic liquids [C6mim][DEHP] and [C6mpyr][DEHP] showed markedly different extraction properties in comparison with that of the quaternary ammonium analogue [N4444][DEHP], especially concerning the pH dependence of the extraction process. These results show that the extraction process can be tuned by the selection of the ionic liquid cation. The extraction experiments also included the trivalent rare-earth ions lanthanum(iii), cerium(iii), praseodymium(iii), ytterbium(iii) and yttrium(iii). Studies of the stripping behavior and the reusability of the ionic liquids were carried out, which indicate that the ionic liquids can be reused with no loss in activity.

Extraction of Asphaltenes from Direct Coal Liquefaction Residue by Dialkylphosphate Ionic Liquids

Asphaltenes in direct coal liquefaction residue (DCLR) are important precursors for the preparation of carbon materials. Some traditional polar hydrocarbon solvents show the ability to extract asphaltenes from DCLR, but these solvents are volatile, toxic, and difficult to recycle. Dialkylphosphate ionic liquids (ILs) have been demonstrated to have the ability to extract asphaltenes fractions from DCLR environmentally friendly. In order to understand the relationship between the extractive performance and the structure of cations and anions of ILs, a series of N,N-dialkylimidazolium dialkylphosphate ILs were synthesized and used to extract asphaltenes from DCLR. The extracts were characterized by Elemental Analysis, FT-IR, 13C-NMR, etc. The results show that it is feasible to extract asphaltenes from DCLR by N,N-dialkylimidazolium dialkylphosphate ILs. The alkyl chain length of cations and anions of the ILs is one factor that influences the extraction yield and the physicochemical characteristics of the extracted asphaltenes, such as the atomic ratio of H/C, true density, aromaticity, and so on. The alkyl chain length of ILs might be modified successfully for controlling the physicochemical characteristics of the extracts from DCLR.

Enzyme activity in dialkyl phosphate ionic liquids

The activity of four metagenomic enzymes and an enzyme cloned from the straw mushroom, Volvariella volvacea were studied in the following ionic liquids, 1,3-dimethylimidazolium dimethyl phosphate, [mmim][dmp], 1-ethyl-3-methylimidazolium dimethyl phosphate, [emim][dmp], 1-ethyl-3-methylimidazolium diethyl phosphate, [emim][dep] and 1-ethyl-3-methylimidazolium acetate, [emim][OAc]. Activity was determined by analyzing the hydrolysis of para-nitrobenzene carbohydrate derivatives. In general, the enzymes were most active in the dimethyl phosphate ionic liquids, followed by acetate. Generally speaking, activity decreased sharply for concentrations of [emim][dep] above 10% v/v, while the other ionic liquids showed less impact on activity up to 20% v/v.

THEORETICAL STUDY ON INTERACTION BETWEEN IONIC LIQUIDS AND AROMATIC SULFUR COMPOUNDS

It is important to understand how ionic liquids interact with aromatic sulfur compounds in view of ionic liquids application in desulfurization from fuels. Ion pairs of N, N-dialkylimidazolium dialkylphosphate ionic liquids were optimized at the Becke3LYP level of density functional theory. The most stable geometries were obtained. The stable ion pairs indicate there exist hydrogen bonding interactions between them. The calculated interaction energies of ion pairs were found to increase in magnitude with decreasing alkyl chain length, and with decreasing anionic radius. Furthermore, the interactions between the IL and aromatic sulfur compound, and benzene molecule were investigated. The results indicate that there exist hydrogen bonds between them. The calculated interaction energy between IL and sulfur compound is larger than that between IL and benzene. The aromatic ring π - π interaction and hydrogen bonding interaction may be the dominant factors to influence the trend of interaction between ILs and aromatic sulfur compounds.

Solubility of CO 2 in dialkylimidazolium dialkylphosphate ionic liquids

The solubility of carbon dioxide in room temperature ionic liquids (RTILs), dialkylimidazolium dialkylphosphates, was measured at 313–333 K and at pressures close to atmospheric pressure, from which Henry's law coefficients, standard Gibbs free energy, enthalpy, and entropy changes of solvation were derived. The CO 2 solubility in the dialkylimidazolium dialkylphosphate was found to increase with increasing chain length of the alkyl groups on the cation and/or the anion as was similarly found in other RTILs. Among various dialkylimidazolium dialkylphosphates tested, 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][Et 2PO 4]) and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][Bu 2PO 4]) exhibited the comparable or better capability of dissolving CO 2 in comparison with that of [BMIM][BF 4], but their absorption capacities were still lower than that of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf 2N]).

N,N-dialkylimidazolium dialkylphosphate ionic liquids: Their extractive performance for thiophene series compounds from fuel oils versus the length of alkyl group

N-butylimidazole-derived dialkylphosphate ionic liquids (ILs) are demonstrated to be effective for extractive removal of aromatic sulfur compounds (S-compounds) from fuel oils, and show strong preferential extraction for aromatic S-compound versus toluene. Sulfur partition coefficients ( K N ) between IL and fuel oil at 298.15 K are determined experimentally over a wide range of sulfur content. The results show that the sulfur removal selectivity for a specific IL is dependent on the molecular structure of the S-compounds and follows the order dibenzothiophene > benzothiophene > thiophene > 3-methylthiophene, and the efficiency of the ILs for removal of aromatic S-compounds is dependent on the size and structure of both cations and anions of the ILs. For the dialkylphosphate ILs studied with the same anion, the longer the alkyl substitute to the imidazolium ring is the higher the K N value for that IL, and a similar trend is found for the ILs with same cation.

Extractive Desulfurization of Fuel Oil Using Alkylimidazole and Its Mixture with Dialkylphosphate Ionic Liquids

The sulfur partition coefficient KN is usually used to characterize the ability of extractive desulfurization (EDS). In this work, several KN values are measured at 298.15 K, which are between straight-run fuel oil and N-ethylimidazole (EIM), N-methylimidazole (MIM), and its mixture with a dialkylphosphate ionic liquid (IL), viz. N-ethyl-N-methylimidazolium diethylphosphate ([EMIM][DEP]) or N-butyl-N-methylimidazolium dibutylphosphate ([BMIM][DBP]). KN values between the oil and solvent at varying water content are also measured at 298.15 K. The results indicate that both EIM and MIM have excellent EDS performance with KN above 3.1 for dibenzothiophene. They have some solubility in fuel oil, but their solubility decreases with addition of IL. The EDS ability of the solvents for a specified sulfur compound followed the order alkylimidazole (EIM > MIM) > mixed solvent (MIM + IL) > IL ([BMIM][DBP] > [EMIM][DEP]); the extractive selectivity of sulfur for a specified solvent followed the order dibenzothiophene...

Imidazolium dialkylphosphates—a class of versatile, halogen-free and hydrolytically stable ionic liquids

In this article a systematic and detailed study on the synthesis and the properties of dialkylphosphate ionic liquids is presented. This class of halogen-free ionic liquids is easily available in high quality and great variability by direct alkylation of nucleophiles, such as 1-methylimidazole, 1-ethylimidazole, 1-butylimidazole and 1-(2-methoxyethyl)-imidazole with different trialkylphosphates, such as trimethylphosphate, triethylphosphate or tributylphosphate. In general, these dialkylphosphate ionic liquids were found to display very attractive physico-chemical properties with great technical potential, especially in low temperature (<200 °C) applications with water present. For this specific application area, the materials described here clearly show superior properties compared with alkylsulfate ionic liquids due to their obviously much higher hydrolytic stability.