Shitao Yu

A Brønsted acidic ionic liquid as an efficient and environmentally benign catalyst for biodiesel synthesis from free fatty acids and alcohols

Biodiesel could be synthesized using Brønsted acidic ionic liquid N-methyl-2-pyrrolidonium methyl sulfonate ([NMP][CH(3)SO(3)]) as a catalyst, specially with free long-chain fatty acids or their mixtures, as well as with low-molecular weight alcohols as substrates. This catalyst showed good catalytic and reusable performance under mild conditions and without any additional organic solvent. The ionic liquid could be reused eight times after the water in the ionic liquid was removed. The yields of fatty acid alkyl esters could reach between 93.6% and 95.3% after the esterifications were carried out at 70 degrees C for 8h. Therefore, an efficient and environmentally friendly catalyst was provided for the synthesis of biodiesel from low-cost feedstocks such as waste oils.

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.

Hydrolysis of polycarbonate catalyzed by ionic liquid [Bmim][Ac]

Hydrolysis of polycarbonate (PC) was studied using ionic liquid 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]) as a catalyst. The influences of temperature, time, water dosage and [Bmim][Ac] dosage on the hydrolysis reaction were examined. Under the conditions of temperature 140°C, reaction time 3.0 h, m([Bmim][Ac]):m(PC)=1.5:1 and m(H(2)O):m(PC)=0.35:1, the conversion of PC was nearly 100% and the yield of bisphenol A (BPA) was over 96%. The ionic liquid could be reused up to 6 times without apparent decrease in the conversion of PC and yield of BPA. The kinetics of the reaction was also investigated. The results showed that the hydrolysis of PC in [Bmim][Ac] was a first-order kinetic reaction with an activation energy of 228 kJ/mol.

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.

Characterization of products from hydrothermal carbonization of pine

This study aims to reveal the structural features and reaction pathways for solid-liquid products from hydrothermal carbonization of Loblolly pine, where the solid products can be used as catalysts, adsorbents and electrode materials while liquid products can be treated yielding fuels and platform chemicals. Results revealed when treated at 240°C, cellulose and hemicellulose were degraded, in part, to 5-hydroxy-methyl furfural and furfural which were further transformed to aromatic structures via ring opening and Diels Alder reactions. Lignin degradation and formation of carbon-carbon bonds, forming aromatic motifs in the presence of furanic compounds connected via aliphatic bridges, ether or condensation reactions. After hydrothermal treatment, condensed aromatic carbon materials with methoxy groups were recovered with high fixed carbon content and HHV. The recovered liquid products are lignin-like value-added chemicals consisting of furfural and polyaromatic structure with alkanes and carboxyl, their total hydroxyl group content decreased when increasing reaction time.

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.

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.

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.