Shiwei Liu

Preparation of high strength chitosan fibers by using ionic liquid as spinning solution

The morphology and mechanical properties of chitosan fibers obtained by wet-spinning using chitosan–[Gly]Cl (glycine chloride) ionic liquid as spinning dope solution are reported for the first time. The objectives were to understand both how the microstructure of the fibers could be modified and how the mechanical properties were improved by means of using [Gly]Cl ionic liquid as the spinning solution. In the new system, the main component chitosan (the degree of deacetylation was 86%, the molecular weight was about 1.5 × 106) was dissolved in an aqueous [Gly]Cl ionic liquid solution; the fibers were then spun using a sodium sulfate (Na2SO4)/ethanol (C2H5OH) aqueous solution as the coagulant, and then directly dried under freeze-drying. The fibers spun from the above mentioned system have the chitosan I crystal form, and the breaking tenacity (3.77 cN dtex−1) is 4 times more than that (0.86 cN dtex−1) from an acetic acid system. The orientation and crystallinity of fibers spun in [Gly]Cl solution was enhanced with an increase of spin stretch ratio, and thereby the mechanical properties of the fibers were improved. Moreover, the fibers had a smooth surface as well as a round and compact structure. More to the point, the used [Gly]Cl could be recovered by simple post processing and the chitosan fibers spun in the recycled [Gly]Cl solution also had a strong breaking tenacity. Therefore, this study verified that [Gly]Cl is a new spinning dope solution for preparing chitosan fibers with strong mechanical properties.

A Brønsted-Lewis Acidic Ionic Liquid: Its Synthesis and Use as the Catalyst in Rosin Dimerization

Bronsted-Lewis acidic ionic liquids 1-(3-sulfoilic acid)-propyl-3-methylimidazole chlorozincinates ([HO(3)S-(CH(2))(3)-mim]Cl-ZnCl(2)) were synthesized and characterized. The characterization results indicated that [HO(3)S-(CH(2))(3)-mim]Cl-ZnCl(2) (molar fraction of ZnCl(2) x > 0.5) had both Bronsted and Lewis acid properties. The catalytic properties of these ionic liquids were investigated using the dimerization of rosin, and it was shown that ionic liquid [HO(3)S-(CH(2))(3)-mim]Cl-ZnCl(2) (x = 0.64) was a good catalyst. Under the optimum conditions for polymerization, i.e., rosin 5.0 g, toluene 15 g, the mass fraction of ionic liquid 5%, reaction temperature 110 degrees C, and reaction time 4 h, a product with the softening point of 118 degrees C was obtained. It was also found that the product was easily separated from the reaction mixture and the ionic liquid catalyst had good reusability.

Porous aerogels prepared by crosslinking of cellulose with 1,4-butanediol diglycidyl ether in NaOH/urea solution

Cellulose aerogels based on crosslinking of cellulose with 1,4-butanediol diglycidyl ether (BDE) were homogeneously synthesized in NaOH/urea aqueous solution followed by freeze-drying. In the NaOH/urea aqueous solution, cellulose existed in a sodium alkoxide form that could react with the epoxide groups of BDE. The rheological behavior of the cellulose/NaOH/urea aqueous solution showed that the crosslinking reaction occurred immediately once the BDE was added to the cellulose/NaOH/urea aqueous solution at room temperature. The X-ray diffraction (XRD) characterization identified a transition from the crystalline structure of cellulose to an amorphous state of cellulose aerogels with increasing amount of BDE. Elemental analysis revealed the variation in carbon and oxygen elemental percentages in cellulose aerogels caused by the reaction between cellulose and BDE. The porous network of aerogels was observed by scanning electron microscopy (SEM) and the pore size of the aerogels increased as a function of BDE. The water adsorbent ability of aerogels was up to 41 g g−1—even after 30 squeezing–adsorption cycles, the water adsorbent ability was still 37 g g−1.

N-terminal PEGylated cellulase: a high stability enzyme in 1-butyl-3-methylimidazolium chloride

A new approach to improve cellulase stability in 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), based on covalently binding the N-terminal α-amino acid residue of commercial cellulase to mPEG-ALD (monomethoxyl-polyethylene glycol aldehyde), is proposed. N-terminal PEGylated cellulase (Cell-ALD) was obtained by using mPEG-ALD as a modifier and by controlling the reaction pH in the range of 4–5. The stability of Cell-ALD was first studied in different concentrations of [Bmim][Cl] at 50 °C and 80 °C. The thermal stability of Cell-ALD was obviously enhanced, and was affected by the molecular weight of mPEG-ALD and the degree of modification (DM). mPEG-ALD 5k (an average molecular weight of 5000 Daltons) increased the stability of the enzyme at 50 °C by more than 30 times compared with the unmodified cellulase in 25% [Bmim][Cl] which behaves as a powerful enzyme deactivating agent. Thus, a stabilized Cell-ALD has been successfully used for the saccharification of dissolved cellulose in [Bmim][Cl] (i.e. up to 95% hydrolysis in 24 h) at 50 °C.

Polymerization of Fatty Acid Methyl Ester Using Acidic Ionic Liquid as Catalyst

Abstract The polymerization of fatty acid methyl ester was investigated using biodiesel as the feed in the presence of a Bronsted-Lewis acidic ionic liquid (IL). A synergetic effect of Bronsted and Lewis acid sites enhanced the catalytic performance of the IL. 1-(3-Sulfonic acid)-propyl-3-methylimidazole chlorozincinate ([HO3S-(CH2)3-mim]Cl-ZnCl2, molar fraction of ZnCl2 was 0.67) was an efficient catalyst for the polymerization. The effects of catalyst amount, reaction temperature, and reaction time were investigated. The optimum conditions for the polymerization were: biodiesel 15 g, m(biodiesel):m(IL) = 15:1, reaction temperature 240 °C, and reaction time 6 h, which gave 63.2% yield of dimeric acid methyl ester. The reusability of the IL was good and after it was used five times, the dimeric acid methyl ester yield was still > 63%.

Hydrolysis of polycarbonate using ionic liquid [Bmim][Cl] as solvent and catalyst

The hydrolysis of polycarbonate (PC) was studied using ionic liquid [Bmim][Cl] as solvent and catalyst. The effects of reaction temperature, water dosage and [Bmim][Cl] dosage on reaction results were examined. It was showed that the hydrolysis conversion of PC was almost 100 % and the yield of bisphenol A (BPA) was over 95 % under the reaction conditions of temperature 165 °C, time 3.0 h, m([Bmim][Cl]):m(PC)=1.5:1 and n(H2O):n(PC)=10:1. The ionic liquid could be reused for 8 times without obvious decrease in the conversion of PC and yield of BPA. Therefore, an environmental friendly strategy for chemical recycling of PC was developed.

Brønsted-Lewis acidic ionic liquid for the “one-pot” synthesis of biodiesel from waste oil

Bronsted–Lewis acidic ionic liquids were employed for the preparation of biodiesel using waste oil as the feedstock. It was found that (3–sulfonic acid)–propyltriethylammonium chloroironinate [HO3S–(CH2)3–NEt3]Cl–FeCl3 (molar fraction of FeCl3 x = 0.67) was an efficient catalyst for the reaction, and a synergetic effect of Bronsted and Lewis acid sites enhanced the catalytic performance of ionic liquid (IL). Using the waste oil with 34.6 mg KOH/g acidic value, the yield of biodiesel was even more than 95% at 120 °C for 4 h. The reusability of IL was good after it was used seven times. Therefore, an efficient and environmentally friendly catalyst is provided for the synthesis of biodiesel from waste oil with high acid value by “one-pot” method.

Mesoporous molecular sieves K2O/Ba(Ca or Mg)-MCM-41 with base sites as heterogeneous catalysts for the production of liquid hydrocarbon fuel from catalytic cracking of rubber seed oil

Mesoporous molecular sieves K2O/Ba(Ca or Mg)-MCM-41, which feature basic sites, were prepared by the coordination effect of ion exchange and impregnation method under hydrothermal conditions, and used as heterogeneous catalysts for the cracking of rubber seed oil (RSO). The structure, base properties and catalytic performance were then studied in detail. The K2O/Ba(Ca or Mg)-MCM-41 exhibited higher catalytic performance than traditional base catalysts such as Na2CO3 and K2CO3. Moreover, the fuels generated from the cracking of RSO have similar chemical compositions to diesel-based fuels and low acid values. The cracking products with low acid values showed good cold flow properties, calorific values and good solubility in diesel oil at low temperature. At the same time, the K2O/Ba(Ca or Mg)-MCM-41 has excellent stability. The catalyst could be recycled and reused with negligible loss in activity over six cycles. The K2O/Ba(Ca or Mg)-MCM-41 is base- and water-tolerant and is an environmentally benign heterogeneous catalyst for the production of liquid hydrocarbon fuels from low quality feed stocks.

Clean Preparation Process of Chitosan Oligomers in Gly Series Ionic Liquids Homogeneous System

Chitosan oligomers because of its water solubility has some special physiological functions, such as binding lipid, affecting the mitogenic response, restraining the growth of tumors, and was widely used in cosmetics and health. H2O2/Gly (Glycine) series ionic liquids system, a new solvable-catalytic system, was an efficient clean process for preparation of chitosan oligomers. The effects of the anions of Gly series ionic liquids on the solubility and degradation for chitosan were investigated, and the results showed that [Gly]Cl aqueous solution was of good solubility and assistant degradation for chitosan. In additional, the mechanism for oxidative degradation of chitosan in ionic liquids (ILs) was studied. The effect on the property of chitosan oligomers catalyzed by H2O2, in two different kinds of solvents (HAc and [Gly]Cl) were compared. It was found that the performance of moisture absorption and retention of chitosan oligomers using ionic liquid aqueous solution as solvent was better than that using HAc aqueous solution as solvent, and even superior to that of hyaluronic acid. Furthermore, [Gly]Cl could be easily separated from the product and reused with only slight loss. It could provide an efficient and environmental friendly method for the preparation of chitosan oligomers in H2O2/ILs system.

Hydrogenation of biodiesel using thermoregulated phase-transfer catalyst for production of fatty alcohols.

The hydrogenation of biodiesel was investigated in presence of thermoregulated phase-transfer catalysts to produce fatty alcohols. The thermoregulated catalytic system Pd/IV (IV: P-ligand, tri-(methoxyl polyethylene glycol)-phosphite) exhibited an efficient catalytic performance for the hydrogenation. It was also found that the steric resistance of the P-ligand, to a large extent, affected the performance of catalytic system. Using Pd/IV as catalyst, the product could be easily separated from the catalytic system and the catalyst was of good reusability. Thus, a clean and environmentally friendly strategy for the production of fatty alcohol is provided.