Li Xuehui

Kinetic model for an esterification process coupled by pervaporation

Abstract A basic kinetic model of an esterification process coupled by pervaporation and a new method for measuring the model parameter had been established. Various effects on the shift of chemical equilibrium of esterification were taken into consideration in this kinetic model. The simulation results of this model coincided well with the experimental results.

Synthesis of a Basic Imidazolide Ionic Liquid and Its Application in Catalyzing Knoevenagel Condensation

Abstract A novel basic ionic liquid paired by 1-butyl-3-methylimidazolium cation and imidazolide anion ([bmim]Im) was synthesized and its basicity was investigated. The basicity of [bmim]Im approaches to that of [bmim]OH and is much stronger than that of [bmim]OAc. In aqueous solution at room temperature, 2% of [bmim]Im showed good catalytic properties for Knoevenagel condensations between aromatic aldehyde and active methylene compounds with 86%-95% yield and 100% selectivity for ylidenemalononitriles. This kind of imidazolide ionic liquid also has better recycle ability.

Ionic liquids: Efficient solvent and medium for the transformation of renewable lignocellulose

Carbon-enriched lignocelluloses are regarded as the perfect alternative for nonrenewable fossil fuel, and have a great potential to alleviate the increasing energy crisis and climate change. However, the tightly covalent structure and strong intra and inter-molecular hydrogen bonding in lignocellulose make it high recalcitrance to transformation due to the poor solubility in water or common organic solvents. Dissolution and transformation of lignocellulose and its constituents in ionic liquids have therefore attracted much attention recently due to the tunable physical-chemical properties. Here, ionic liquids with excellent dissolving capability for biomass and its ingredients were examined. The technologies for lignocellulose biorefining in the presence of ionic liquid solvents or catalysts were also summarized. Some pertinent suggestions for the future catalytic conversion and unitization of this sustained carbon-rich resource are proposed.

Composite electrolytes based on poly(ethylene oxide) and binary ionic liquids for dye-sensitized solar cells

The sunlight is the largest single available source of clean and renewable energy to ensure human society’s sustainable development. Owing to their low production cost and high energy conversion efficiency, dye-sensitized solar cells (DSSCs) have been regarded as good alternatives to conventional photovoltaic devices. Herein, a series of composite electrolytes based on poly(ethylene oxide) (PEO) and the binary ionic liquids 1-propyl-3-methy-imidazolium iodide ([PMIm]I) and 1-ethyl-3-methylimidazolium thiocyanate ([EMIm][SCN]) were prepared and then applied to fabricate six DSSCs. The composite electrolytes were characterized by fourier transform infrared spectroscopy (FTIS), X-ray diffraction (XRD), and electrochemical impedance spectra (EIS). It was shown that the addition of binary ionic liquids would reduce the degree of crystallinity of PEO, thus improving the ionic conductivities of the electrolytes by about 2 orders of magnitude. Investigation on the photovoltaic performances of these DSSCs showed that the fill factor (FF) could reach up to 0.67 and energy conversion efficiency (η) could reach up to 4.04% under AM 1.5 full sunlight (100 mW/cm2).

Catalytic Decomposition of Cellulose in Cooperative Ionic Liquids

Cellulose, the abundant and cost-ineffective resource, is considered to be a perfect alternative for the alleviation of energy crisis and environmental pollution. However, most processes for the treatment of cellulose are rigor currently as it is insoluble in water and conventional organic solvents due to its strong intra and inter-molecular hydrogen bonds, where the phase problem hampers its utilization widely. Here, we built a novel and efficient cooperative ionic liquid pairs system for the low temperature catalytic conversion of cellulose, which was constructed through the combination of an acidic ionic liquid catalyst and a cellulose soluble ionic liquid solvent. The catalytic decomposition behavior of microcrystal cellulose in this vigorous catalytic system was studied intensively by thermogravimetry (TG). Results show that the decomposition temperature of cellulose decreases greatly in all cooperative ionic liquid pairs, cellulose dissolved in ionic liquid solvents can be in situ catalytic decomposed by acidic ionic liquids. Furthermore, the decomposition temperature is dependent on the acidic strength of the ionic liquid catalysts, stronger acidity results in a lower decomposition temperature of the cellulose. Moreover, we found that cellulose can be decomposed at lower temperature when the ionic liquid with higher solubility of cellulose is used.

Catalytic Synthesis of Trimethylolpropane in the Presence of Basic Ionic Liquid

Ionic liquid (IL) catalyst attracts increasing attention during last few decades due to its excellent advantages of both homogeneous and heterogeneous catalyst. Here, a novel and efficient strategy for the production of trimethylolpropane (TMP) is proposed with basic IL catalysts. The catalytic activities of the IL catalysts are investigated. The effects of catalyst dosage, reaction temperature, time, and the molar ratio of the reactants are also studied. The results show that the basicity of the IL catalyst has a significant effect on the catalytic activity, where stronger basicity indicates higher catalytic activity. The IL 1-butyl-3-methyl imidazolium hydroxyl ([bmim]OH) is proven to be the most efficient catalyst where more than 84% isolated yield of TMP was obtained under optimized conditions. Furthermore, both the IL catalyst and butyraldehyde show excellent recyclability. Moreover, this IL catalytic system avoids the inevitable desalination encountered by current processes utilizing inorganic alkali catalysts.

2-Pyrrolidinecarboxylic Acid Ionic Liquid Catalyzed Knoevenagel Condensation

Abstract The pyrrolidinecarboxylic functionalized ionic liquid, 1-butyl-3-methylimidazolium-(S)-2-pyrrolidinecarboxylic acid salt ([bmim][Pro]), was prepared using an improved procedure. α,β-Unsaturated carbonyl compounds were selectively synthesized and high yields (88%–97%) were obtained at room temperature in aqueous media when [bmim][Pro] was used as the catalyst for the Knoevenagel reaction between a methylene compound and an aldehyde or ketone. [bmim][Pro] was reused six times without loss of catalytic activity. The catalytic mechanism is briefly discussed.