Ye Xie

Conversion of fructose to 5-hydroxymethylfurfural using ionic liquids prepared from renewable materials

Efficient conversion of fructose to 5-hydroxymethylfurfural is a key step for using carbohydrates to produce liquid fuels and value-added chemicals. Here we show that some ionic liquids synthesized from cheap renewable materials are very efficient for the conversion of fructose to HMF. The yield and selectivity could be higher than 90% as the reaction was conducted in an ethyl acetate/renewable IL biphasic system and the separation process had no cross-contamination. Moreover, the IL can be reused easily.

Supported choline chloride/urea as a heterogeneous catalyst for chemical fixation of carbon dioxide to cyclic carbonates

In this work, the catalytic efficiency of ionic liquid (IL) choline chloride/urea supported on molecular sieves for the reactions of CO2 and epoxides was studied under different conditions. It was demonstrated that this biodegradable and green catalyst is very active and selective, and choline chloride and urea showed a synergetic effect in promoting these reactions. After reaction, the solid catalyst and the products could be separated easily because the IL was insoluble in the products, and the catalyst was reusable. The origin of the high catalytic efficiency and the reaction mechanism were also discussed.

Synthesis of cyclic carbonates from epoxides and CO2 catalyzed by potassium halide in the presence of β-cyclodextrin

Development of efficient, cheap and non-toxic catalysts for cycloaddition of CO2 with epoxides to produce five-membered cyclic carbonates under greener reaction conditions is still a very attractive topic. In this work, cycloaddition of CO2 with propylene oxide (PO) to propylene carbonate (PC) catalyzed by potassium halide (KCl, KBr, and KI) in the presence of β-cyclodextrin was studied at various conditions. It was discovered that potassium halide and β-cyclodextrin (β-CD) showed excellent synergetic effect in promoting the reactions, and KI-β-CD catalytic system was the most efficient among them. The optimal temperature for the reaction was around 120 °C, and the reaction rate reached maximum at about 6 MPa at this temperature. The reaction could be completed in 4 h with very high selectivity. The decrease of the yield of PC was not noticeable after KI-β-CD was reused five times, indicating that the catalyst was very stable. KI-β-CD catalytic system was also very active and selective for cycloaddition of CO2 with other epoxides, such as glycidyl phenyl ether, epichlorohydrin, and styrene oxide. The mechanism for the synergetic effect is discussed.

Switching the basicity of ionic liquids by CO2

The basicity of several basic ionic liquids is studied quantitatively for the first time, and the basicity of the ionic liquids can be switched repeatedly by bubbling CO2 and N2 through the solution alternately.

Effect of CO2 on conversion of inulin to 5-hydroxymethylfurfural and propylene oxide to 1,2-propanediol in water

The CO2–water system has the potential to serve as a substitute for mineral acids for some reactions in acidic media. In this work, two reactions under hydrothermal conditions with and without CO2 were studied – the conversion of inulin to 5-hydroxymethylfurfural (5-HMF), and the hydrolysis of propylene oxide to 1,2-propanediol (1,2-PDO). The effects of CO2 pressure, reaction temperature and reactant concentration on the yield of 5-HMF and 1,2-PDO were examined. It was demonstrated that CO2 could increase the yields of 5-HMF and 1,2-PDO considerably under optimized conditions. The methods to prepare 5-HMF and 1,2-PDO are greener, in that conventional acids are not required and the solution is neutralized automatically after depressurization.

Aerobic oxidation of benzyl alcohol in supercritical CO2 catalyzed by perruthenate immobilized on polymer supported ionic liquid

The catalyst for aerobic oxidation of benzyl alcohol to produce benzyl aldehyde was prepared by immobilization of perruthenate on polymer supported 1-vinyl-3-butyl imidazolium chloride, and the catalytic reaction was conducted in supercritical (SC) CO2, toluene and dichloromethane at 80 °C. The phase behavior of the reaction system with SC CO2 as solvent was also determined. It was demonstrated that the catalyst was very active and highly selective. The reaction rate in SC CO2 depended strongly on pressure and reached a maximum at about 14 MPa, which can be explained by the effect of pressure on the phase behavior of the reaction system, diffusivity of the components and solvent power of SC CO2. The catalyst could be reused directly after extraction of the products using SC CO2, and it was still active after several runs, although the yield decreased continuously with run times. This work integrated the advantages of green solvent, green supporting material and green oxidant.