Suqin Hu

Efficient conversion of glucose into 5-hydroxymethylfurfural catalyzed by a common Lewis acid SnCl4 in an ionic liquid

The common Lewis acid SnCl4 could efficiently convert glucose into 5-hydroxymethylfurfural in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMim]BF4). New evidence indicated that the formation of the five-membered-ring chelate complex of the Sn atom and glucose may play a key role for the formation of HMF, and the mechanism for the reaction was proposed. In addition, the [EMim]BF4/SnCl4 system was also suitable for the conversion of fructose, sucrose, inulin, cellobiose and starch.

MOF-5/n-Bu4NBr: an efficient catalyst system for the synthesis of cyclic carbonates from epoxides and CO2 under mild conditions

The development of efficient heterogeneous catalysts for the cycloaddition of CO2 with epoxides to produce five-membered cyclic carbonates under mild reaction conditions is of great importance. In this work, the coupling reaction of CO2 with propylene oxide (PO) to produce propylene carbonate (PC) catalyzed by MOF-5 (metal-organic frameworks) in the presence of quaternary ammonium salts (Me4NCl, Me4NBr, Et4NBr, n-Pr4NBr, n-Bu4NBr) was studied in different conditions. It was discovered that MOF-5 and quaternary ammonium salts had excellent synergetic effect in promoting the reaction, and the MOF-5/n-Bu4NBr catalytic system was the most efficient among them. The optimal temperature for the reaction was around 50 °C. The reaction could be completed in 6 h at low CO2 pressure with very high selectivity. A decrease of the yield of PC was not noticeable after MOF-5 was reused three times, indicating that the MOF-5 was stable. The MOF-5/n-Bu4NBr catalytic system was also very active and selective for the cycloaddition of CO2 with other epoxides, such as glycidyl phenyl ether, epichlorohydrin and styrene oxide. The mechanism for the coupling reaction is also discussed.

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.

Direct conversion of inulin to 5-hydroxymethylfurfural in biorenewable ionic liquids

In this work, we found that inulin is soluble in ionic liquids (ILs) choline chloride (ChoCl)/oxalic acid and ChoCl/citric acid, which are prepared entirely from cheap and renewable materials. On the basis of this discovery, we conducted the one pot reaction for the conversion of inulin into 5-hydroxymethylfurfural (HMF), which is a potential substitute for petroleum-based building blocks, using the two ILs as catalysts and solvents. The effects of reaction time, temperature and water added on the reaction were studied. It is demonstrated that the ILs are very efficient for the reaction at relatively lower temperature and could be reused after simple separation.

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.

Hydrogenation of CO2 to Formic Acid Promoted by a Diamine‐Functionalized Ionic Liquid

Amines to an end: The basic diamine-functionalized ionic liquid 1,3-di(N,N-dimethylaminoethyl)-2-methylimidazolium trifluoromethanesulfonate was prepared and used in the hydrogenation of CO(2) to formic acid. One mole of the ionic liquid coordinates two moles of formic acid to promote the reaction. Both the ionic liquid and catalyst can be reused directly after their separation from the formic acid produced.

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.

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.

CO2-controlled reactors: epoxidation in emulsions with droplet size from micron to nanometre scale

The epoxidation of styrene in the cetyltrimethylammonium bromide (CTAB)/H2O/heptane/styrene/H2O2 emulsion system was investigated in the presence of compressed CO2. It was found that by controlling the CO2 pressure, the emulsion droplets can be changed in a wide range from micron to nanometre size; accordingly, the conversion was enhanced significantly with the reduced droplet size. At 5.27 MPa, the conversion in the emulsion (with droplet size of 39.5 nm) could be about 10 times higher than that in a surfactant-free system at the same pressure. The effects of other experimental conditions of CTAB concentration, reaction time, styrene concentration, amounts of H2O2, and alkalinity on the efficiency of the epoxidation were also studied, and a possible mechanism for the enhanced reaction efficiency with reduced droplet size was presented. This process has some unique advantages. For example, the reactant conversion can be easily tuned by controlling the pressure of CO2; CO2 can be used as bicarbonate source and no additional catalyst was used; CO2 can be easily removed by depressurization; the separation for the product is simple. It is believed that the CO2-tuned emulsions can be easily applied to many other chemical reactions.