Congxia Xie

Synthesis of plasticizer ester using acid-functionalized ionic liquid as catalyst.

Several plasticizer esters were synthesized by using acid-functionalized ionic liquids as catalyst. The results indicated that HSO3-functionalized Brønsted acidic ionic liquids show better catalytic and reusable performance than non-functionalized ionic liquids. For each plasticizer ester examined, one or two ionic liquids with high catalytic activity were chosen. Especially, the ionic liquids could be separated easily from the products and be reused at least six times with the conversion of the acid not less than 95%. Therefore, an environmental friendly approach for the synthesis of plasticizer ester is provided.

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.

Process of lignin oxidation in an ionic liquid coupled with separation

A novel approach has been developed in order to use lignin as a renewable resource for the production of a high added-value aromatic aldehyde. The concept is based on the use of an ionic liquid as a reversible medium coupled with the separation process, which prevents the aromatic aldehyde products from oxidizing and increases their yields. The conversion of lignin reached 100%, and the total yield of the aromatic aldehydes (vanillin, syringaldehyde and p-hydroxybenzaldehyde) was 29.7% in the coupled process. In addition, the mixture of product and IL phase was easily separated, and the IL phase demonstrated good reusability. Hence, a clean and environmentally friendly strategy for overall utilization of lignin and preparation of an aromatic aldehyde is developed.

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.

Mild water-promoted ruthenium nanoparticles as an efficient catalyst for the preparation of cis-rich pinane

Ruthenium (Ru) nanoparticles were prepared using polyoxyethylene–polyoxypropylene–polyoxyethylene triblock copolymer (P123) micelles in water as a stabilizing agent. The P123–Ru micellar catalyst was first used in the hydrogenation of α-pinene to pinane, and the selectivity for cis-pinane reached 98.9%. This result is attributed to the formation of vesicles. The isolated catalyst phase could be used seven times with no treatment, and its catalytic activity and selectivity were almost unchanged. The preparation process of the catalyst and hydrogenation reaction of α-pinene was under mild and environmentally friendly conditions. This research offers an effective method for the hydrogenation of α-pinene and provides a reference for other hydrophobic natural products in hydrogenation reactions.

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.

Imidazolium chiral ionic liquid derived carbene-catalyzed conjugate umpolung for synthesis of γ-butyrolactones

A serial of imidazolium chiral ionic liquids starting from commercially available (−)-menthol as a chiral pool have been synthesized and successfully used for catalyzing conjugate umpolung of α,β-unsaturated aldehydes to stereoselectively synthesize γ-butyrolactones. The catalytic activities of these ionic liquids are examined and compared. The reaction of trans-cinnamaldehyde and p-methoxycarbonyl benzaldehyde as a model has been investigated in detail, and the reaction conditions have been optimized. Under the selected conditions, the ionic liquid catalyst can catalyze the annulations of trans-cinnamaldehyde with different aromatic aldehydes to afford differently substituted γ-butyrolactones. The recyclability of the ionic liquid catalyst is investigated, and the results have indicated that the catalyst can be recycled six times without obvious activity decreasing.

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%.

Selective hydrogenation of α-pinene to cis-pinane over Ru nanocatalysts in aqueous micellar nanoreactors

D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS-1000) stabilized Ru(0) nanoparticles were prepared and characterized. These nanoparticles were employed to selectively hydrogenate α-pinene to cis-pinane. With a small amount of Na2CO3 present, reaction rates could be increased significantly, and the reaction medium could be readily recycled. TEM, CLSM, IR and leaching experiments were employed to quantify the advantages of the catalytic system. The procedure is environmentally friendly. It offers a reference for the catalytic hydrogenation of other hydrophobic natural products.

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.