Peifang Yan

Esterification of glycerol with acetic acid using double SO3H-functionalized ionic liquids as recoverable catalysts

Esterification of glycerol with acetic acid was studied using a series of Bronsted acidic ionic liquids as catalysts. The results indicate that double SO3H-functionalized ionic liquids show high catalytic activity and fair reusability even at very low catalyst loadings, while the conventional non-functionalized ionic liquids show poor activity. The Bronsted acidity–catalytic activity relationships were also investigated and the results showed that the sequence of the catalytic activity observed in the transformation was in good agreement with the Bronsted acidity order determined by the Hammett method.

An ionic liquid–organics–water ternary biphasic system enhances the 5-hydroxymethylfurfural yield in catalytic conversion of glucose at high concentrations

Increasing the glucose loading in the 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid containing a dissolved CrCl3 catalyst system led to excessive formation of humins and a serious decrease in the 5-hydroxymethylfurfural (5-HMF) yield. A biphasic system containing glycol dimethyl ether (GDE) as the extraction phase, and [BMIM]Cl/CrCl3/glucose in combination with a partitioned amount of GDE and an appropriate amount of water as the reaction phase was found to be highly efficient for the reaction; CrCl3 catalyzed the formation of 5-HMF in 64.5 mol% yield from a very high glucose concentration (80 wt% with respect to the ionic liquid) at 108 °C. This 5-HMF yield in the [BMIM]Cl–GDE–H2O ternary biphasic system nearly doubled that obtained in the single [BMIM]Cl/CrCl3/glucose reaction phase. Importantly, the GDE phase contained about 56% of the generated 5-HMF without detectable contamination by the ionic liquid or carbohydrates. GDE served multiple functions: as a hydrogen-bond acceptor, it exhibited excellent extraction performance for 5-HMF; due to its low boiling point and suitable solubility saturation point in the ionic liquid, a sustained GDE bubbling phenomenon in the ionic liquid phase was observed that promoted the rate of inter-phase mass-transfer of 5-HMF in reactions; and GDE mediated the [BMIM]Cl phase to a reduced viscosity. In addition, an appropriate amount of water in the ternary system promoted the extraction efficiency of 5-HMF and also lowered the viscosity of [BMIM]Cl/glucose. The ionic liquid–organics–water ternary biphasic system has been demonstrated for high 5-HMF productivity and separation efficiency.

Fractionation of lignin from eucalyptus bark using amine-sulfonate functionalized ionic liquids

A series of amine-sulfonate functionalized ionic liquids (ASF-ILs) were synthesized, characterized, and evaluated for the dissolution of model biopolymers (cellulose, xylan, kraft lignin and lignosulfonate). The ASF-ILs were prepared in high atomic efficiency. Most of the ASF-ILs dissolve kraft lignin and lignosulfonate efficiently at 373 K, with solubilities of 0.220–0.385 g for kraft lignin and of 0.150–0.290 g for lignosulfonate per gram of ASF-ILs. In contrast, xylan and cellulose are scarcely soluble (<5 mg g−1) in the ASF-ILs. Based on the results of the model lignin dissolution, four most promising ASF-ILs were selected and applied for the pretreatment of eucalyptus bark. The lignin was selectively fractionated by the ASF-ILs (393 K for 10 h, lignin removal was more than 40%). The fractionated lignin and the eucalyptus bark residues were then characterized by infrared spectroscopy and thermogravimetric analysis. Importantly, we demonstrate that enzymatic hydrolysis of the polysaccharide components of the eucalyptus bark to sugars was substantially enhanced after the pretreatment, most pronouncedly with the ASF-IL[Et4N][Me2NC4SO3].

Direct reductive amination of 5-hydroxymethylfurfural with primary/secondary amines via Ru-complex catalyzed hydrogenation†

In this work, the complex dichlorobis(2,9-dimethyl-1,10-phenanthroline)ruthenium(II) (Ru(DMP)2Cl2) was found to effectively catalyze the direct reductive amination of bio-based 5-hydroxymethylfurfural (5-HMF) in the presence of H2 (g) in ethanol solvent. Good product yields (66–95%) were obtained from a broad substrate scope of primary and secondary amines.

A catalytic aldol condensation system enables one pot conversion of biomass saccharides to biofuel intermediates

Producing bio-intermediates from lignocellulosic biomass with minimal process steps has a far-reaching impact on the biofuel industry. We studied the metal chloride catalyzed aldol condensation of furfural with acetone under conditions compatible with the upstream polysaccharide conversions to furfurals. In situ far infrared spectroscopy (FIR) was applied to guide the screening of aldol condensation catalysts based on the distinguishing characteristics of metal chlorides in their coordination chemistries with carbonyl-containing compounds. NiCl2, CoCl2, CrCl3, VCl3, FeCl3, and CuCl2 were selected as the potential catalysts in this study. The FIR results further helped to rationalize the excellent catalytic performance of VCl3 in furfural condensation with acetone, with 94.7% yield of biofuel intermediates (C8, C13) in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solvent. Remarkably, addition of ethanol facilitated the acetal pathway of the condensation reaction, which dramatically increased the desired product selectivity over the furfural pathway. Most significantly, we demonstrate for the first time that VCl3 catalyzed aldol condensation in acidic medium is fully compatible with upstream polysaccharide hydrolysis to monosaccharide and the subsequent monosaccharide isomerization and dehydration to furfurals. Our preliminary results showed that a 44% yield of biofuel intermediates (C8, C13) can be obtained in one-pot conversion of xylose catalyzed by paired metal chlorides, CrCl2 and VCl3. A number of prior works have shown that the biofuel intermediates derived from the one-pot reaction of this work can be readily hydrogenated to biofuels.

Lignocellulosic ethanol production by starch-base industrial yeast under PEG detoxification.

Cellulosic ethanol production from lignocellulosic biomass offers a sustainable solution for transition from fossil based fuels to renewable alternatives. However, a few long-standing technical challenges remain to be addressed in the development of an economically viable fermentation process from lignocellulose. Such challenges include the needs to improve yeast tolerance to toxic inhibitory compounds and to achieve high fermentation efficiency with minimum detoxification steps after a simple biomass pretreatment. Here we report an in-situ detoxification strategy by PEG exo-protection of an industrial dry yeast (starch-base). The exo-protected yeast cells displayed remarkably boosted vitality with high tolerance to toxic inhibitory compounds, and with largely improved ethanol productivity from crude hydrolysate derived from a pretreated lignocellulose. The PEG chemical exo-protection makes the industrial S. cerevisiae yeast directly applicable for the production of cellulosic ethanol with substantially improved productivity and yield, without of the need to use genetically modified microorganisms.

Synthesis of Bis(hydroxylmethylfurfuryl)amine Monomers from 5-Hydroxymethylfurfural

We report the synthesis of bis(hydroxylmethylfurfuryl)amine (BHMFA) from 5-hydroxymethylfurfural (5-HMF) by reacting 5-HMF with primary amines in the presence of homogeneous Ru(II) catalysts having sterically strained ligands. BHMFA is a group of furan-based monomers that offer great potential to form functional biopolymers with tunable properties. A range of primary amines, such as aliphatic and benzyl amines, are readily converted with 5-HMF to form the corresponding BHMFA in good yields. The reaction proceeds through reductive amination of 5-HMF with primary amine to form secondary amine, followed by reductive amination of 5-HMF with in situ generated secondary amine to produce BHMFA.

Vitalized yeast with high ethanol productivity

Fuel ethanol is an attractive alternative to fossil-based fuels or fuel additives. Very-high-gravity (VHG) ethanol fermentation is a promising technology to reduce energy consumption in distillation. However, yeast cells subjected to a high concentration of ethanol and osmotic stress readily lose cell viability, resulting in reduced ethanol productivity. Here we report the beneficial effect of fully water-soluble polyethylene glycol (PEG) in chemically exo-protecting yeast cells during fermentation, resulting in largely boosted cell vitality and tolerance to high ethanol concentration. The final ethanol concentration and the yeast cell viability were substantially increased as compared to PEG-free fermentation. The recovered exo-protected yeast was further demonstrated to continue to deliver superior bio-catalytic performance in subsequent fermentations over that recovered from PEG-free broth. Furthermore, the water-soluble PEG was readily recycled for reuse after distillation of ethanol.

A green and efficient amine-functionalized ionic liquid/H2O catalytic system for the synthesis of α,α′-bis(substituted benzylidene)cyclopentanones

An environmentally benign and convenient amine-functionalized ionic liquid (IL) catalytic system was explored for the preparation of α,α′-bis(substituted benzylidene)cyclopentanones by the cross-aldol condensation of aromatic aldehydes with cyclopentanone. High yields were obtained without using any organic solvents. The condensation products can be separated easily and the ILs can be recovered and reused at least five times without apparently loss of activity. The potential mechanism of the cross-aldol condensation reaction in this IL catalytic system is discussed.

Thermodynamic Properties of Ionic Liquids - Measurements and Predictions -

Research of ionic liquids (ILs) is one of the most rapidly growing fields in the past years, focusing on the ultimate aim of large scale industrial applications. Due to their unique tunable properties, such as negligible vapor pressure at room temperature, stable liquid phase over a wide temperature range and thermal stability at high temperatures, ionic liquids are creating an continuously growing interest to use them in synthesis and catalysis as well as extraction processes for the reduction of the amount of volatile organic solvents (VOSs) used in industry. For the general understanding of these materials it is of importance to develop characterization techniques to determine their thermodynamic and physicochemical properties as well as predict properties of unknown Ionic Liquids to optimize their performance and to increase their potential future application areas. Our laboratory in cooperation with several national and international academic and industrial partners is contributing to these efforts by the establishment of various dedicated characterization techniques (like activity coefficient measurements using GC technology) as well as determination of thermodynamic and physicochemical properties from a continuously growing portfolio of (functionalized) ionic liquids. Based on the received property data we published several papers related to the adjacent prediction of properties (like molar enthalpy of vaporization, parachor, interstice volume, interstice fractions, thermal expansion coefficient, standard entropy etc.). Additionally our laboratory created and launched a new most comprehensive Ionic Liquid property data base--delphIL.(www.delphil.net). This fast growing collections of IL data will support researchers in the field to find and evaluate potential materials for their applications and hence decrease the time for new developments. In this chapter we introduce the following techniques, summarize recent published results completed by our own investigations: 1. Activity coefficient measurements using GC technique, 2. Thermodynamic properties determined by adiabatic calorimetry and thermal analysis (DSC, TG-DTG). 3. Estimation and prediction of physicochemical properties of ILs based on experimental density and surface tension data.