Xingmei Lu

Physical Properties of Ionic Liquids: Database and Evaluation

A comprehensive database on physical properties of ionic liquids (ILs), which was collected from 109 kinds of literature sources in the period from 1984 through 2004, has been presented. There are 1680 pieces of data on the physical properties for 588 available ILs, from which 276 kinds of cations and 55 kinds of anions were extracted. In terms of the collected database, the structure-property relationship was evaluated. The correlation of melting points of two most common systems, disubstituted imidazolium tetrafluoroborate and disubstituted imidazolium hexafluorophosphate, was carried out using a quantitative structure-property relationship method.

Dual Amino‐Functionalised Phosphonium Ionic Liquids for CO2 Capture

A series of 20 dual amino-functionalised phosphonium ionic liquids, (3-aminopropyl)tributylphosphonium amino acid salts ([aP(4443)][AA], in which [AA](-) = [Ala](-), [Arg](-), [Asn](-), [Asp](-), [Cys](-), [Gln](-), [Glu](-), [Gly](-), [His](-), [Ile](-), [Leu](-), [Lys](-), [Met](-), [Phe](-), [Pro](-), [Ser](-), [Thr](-), [Trp](-), [Tyr](-) and [Val](-)), has been prepared. Their physicochemical properties, such as density, viscosity, glass transition and thermal decomposition temperatures and conductivity, have been determined. In particular, the [aP(4443)][AA] ionic liquids (ILs) have low glass transition temperatures ranging from -69.7 to -29.6 degrees C and high decomposition temperatures (all above 200 degrees C). The effects of the variation of the structure of [AA](-) on the above physicochemical properties are discussed. Furthermore, the CO(2) absorption of [aP(4443)][Gly], [aP(4443)][Ala], [aP(4443)][Val] and [aP(4443)][Leu], taken as examples, was investigated. It was found that the supported absorption of CO(2) by the [aP(4443)][AA] ILs almost reaches equilibrium within 80 min, the chemical absorption of CO(2) by the [aP(4443)][AA] ILs approaches 1 mol CO(2) per mol ionic liquid (twice that reported before) and the [aP(4443)][AA] ILs can be repeatedly recycled for CO(2) uptake.

Dissolution or extraction of crustacean shells using ionic liquids to obtain high molecular weight purified chitin and direct production of chitin films and fibers

1-Ethyl-3-methyl-imidazolium acetate can completely dissolve raw crustacean shells, leading to recovery of a high purity, high molecular weight chitin powder and to fibers and films which can be spun directly from the extract solution.

Biodegradable Naphthenic Acid Ionic Liquids: Synthesis, Characterization, and Quantitative Structure–Biodegradation Relationship

It has been confirmed that commonly used ionic liquids are not easily biodegradable. When ultimately disposed of or accidentally released, they would accumulate in the environment, which strongly restricts large-scale industrial applications of ionic liquids. Herein, ten biodegradable ionic liquids were prepared by a single, one-pot neutralization of choline and surrogate naphthenic acids. The structures of these naphthenic acid ionic liquids (NAILs) were characterized and confirmed by (1)H and (13)C NMR spectroscopy, IR spectroscopy, and elemental analysis, and their physical properties, such as densities, viscosities, conductivities, melting points (T(m)), glass transition points (T(g)), and the onset temperatures of decomposition (T(d)), were determined. More importantly, studies showed that these NAILs would be rapidly and completely biodegraded in aquatic environments under aerobic conditions, which would make them attractive candidates to be utilized in industrial processes. To explore the underlying mechanism involved in the NAIL biodegradation reaction and seek prediction of their biodegradability under environmental conditions, four molecular descriptors were chosen: the logarithm of the n-octanol/water partition coefficient (log P), van der Waals volume (V(vdW)), energies of the highest occupied molecular orbital (E(HOMO)), and energies of the lowest unoccupied molecular orbital (E(LUMO)). Through multiple linear regression, a general and qualified model including the biodegradation percentage for NAILs after the 28-day OECD 301D test (%B(28)) and molecular descriptors was developed. Regression analysis showed that the model was statistically significant at the 99 % confidence interval, thus indicating that the %B(28) of NAILs could be explained well by the quantum chemical descriptor E(HOMO), which might give some important clues in the discovery of biodegradable ionic liquids of other kinds.

A new theory for ionic liquids—the Interstice Model

This paper reports measurements of the surface tension of ionic liquid EMISE (1-ethyl-3-methylimidazolium ethyl sulfate) using the forced bubble method at 278.15 to 323.15 K and densities of EMISE using a Westphal balance at 278.15 to 338.15 K. At the same time, a new theoretical model, the interstice model, is put forward. Applying the model, an expression of the average volume of the interstices, v, was obtained. The calculated volume fraction of the total interstices is 0.12 for ionic liquid EMISE and is in good agreement with that of the majority of materials which exhibit a 10∼15% volume expansion in transition from the solid to liquid state. The value of the thermal expansion coefficient calculated from the model is 5.24 × 10−4 K−1 and is in good agreement with the experimental value 5.37 × 10−4 K−1 at 298.15 K.

Rapid dissolution of lignocellulosic biomass in ionic liquids using temperatures above the glass transition of lignin

Rapid dissolution of bagasse and southern yellow pine has been achieved in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) by using a dissolution temperature above the glass transition of lignin (ca. 150 °C). When 0.5 g of bagasse or pine is added to 10 g of [C2mim]OAc, complete dissolution can be obtained in 5–15 min for bagasse at a temperature of 175–195 °C, compared to 15–16 h at 110 °C, and over 90% of added pine can be dissolved with heating at 175 °C for 30 min. Upon regeneration in acetone/water, lignin and carbohydrate can be partially separated as lignin and a cellulose-rich material (CRM, pulp). Compared to published methods with lower temperatures and longer times (e.g., 110 °C, 16 h), processing bagasse in [C2mim]OAc at 185 °C for 10 min results in higher yields of both recovered lignin (31% vs. 26% of the available lignin) and carbohydrate (carbohydrate yield = 66% vs. 63% of the available carbohydrate). In addition, the CRM pulp recovered using the higher temperature method has much lower residual lignin content (6% vs. 20%). Similar results were obtained for pine (lignin content in CRM with higher vs. lower temperature method = 16.1% vs. 23.5%). The IL was recycled and reused although the efficiency decreased and ca. 15% of the IL had degraded after the higher temperature process. These latter results suggest further optimization of the choice of IL and heating conditions might be needed to develop an energy and chemical efficient process.

A strategy for synthesis of ionic metal-organic frameworks.

For the first time, we designed and synthesized a new kind of ionic metal-organic framework with lanthanide ions and a carboxyl-functionalized ionic liquid, including [Er(4)(mu(3)-OH)(4)(mu(2)-O)(0.5)OL(4)(H(2)O)(3)] x Br(2.90) x Cl(1.10) x 2 H(2)O (MOF-1) and [PrL(H(2)O)(4)Cl] x Br x H(2)O(MOF-2).

Coagulation of Chitin and Cellulose from 1‐Ethyl‐3‐methylimidazolium Acetate Ionic‐Liquid Solutions Using Carbon Dioxide

Chemisorption of carbon dioxide by 1-ethyl-3-methylimidazolium acetate ([C2 mim][OAc]) provides a route to coagulate chitin and cellulose from [C2 mim][OAc] solutions without the use of high-boiling antisolvents (e.g., water or ethanol). The use of CO2 chemisorption as an alternative coagulating process has the potential to provide an economical and energy-efficient method for recycling the ionic liquid.

Formation of C–C bonds for the production of bio-alkanes under mild conditions

It is of crucial importance to form C–C bonds between biomass-derived compounds for the production of bio-alkanes from biomass. In this study, it was found that C–C bonds can be formed between angelica lactones, key intermediates derived from biomass, through free radical reactions under mild conditions without using a noble catalyst or solvent, which gave elongated carbon chains of di/trimers with 10 or 15 carbons, with complete conversion and 100% selectivity. The di/trimers produced serve as a novel feedstock for the carbon backbones of bio-alkanes. Hydrogenation of the di/trimers produced C6–C13 hydrocarbons suitable for use as transportation fuels.

Composite fibers spun directly from solutions of raw lignocellulosic biomass dissolved in ionic liquids

Lignocellulosic biomass composite fibers (southern yellow pine and bagasse) were successfully prepared directly from the ionic liquid, 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) with a dry-jet wet spinning process using short dissolution times (10–30 min) and temperatures above the glass transition temperature of lignin. Fibers could not be spun at all from solutions of pine dissolved using previously reported dissolution methods (110 °C, 16 h), while bagasse fibers spun using the higher temperature/shorter time method were stronger than those obtained using the lower temperature/longer time method.