Zhaofu Zhang

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.

Absorption of CO2 by ionic liquid/polyethylene glycol mixture and the thermodynamic parameters

Absorption/desorption of CO2 by ionic liquid (IL) where both cation and anion are from renewable materials, (2-hydroxyethyl)-trimethyl-ammonium (S)-2-pyrrolidine-carboxylic acid salt [Choline][Pro], and [Choline][Pro]/polyethylene glycol 200 (PEG200) mixture, were studied in the 308.15 K to 353.15 K range at ambient pressure. It was demonstrated that both the neat ionic liquid (IL) and the IL/PEG200 mixture could capture CO2 effectively and could be easily regenerated under vacuum or by bubbling nitrogen through the solution, and the molar ratio of CO2 to the IL could exceed 0.5 slightly, which is the theoretical maximum for absorption of CO2 chemically, indicating that both chemical and physical absorption existed. Addition of PEG200 in the IL could enhance the rates of absorption and desorption of CO2 significantly. The solubility of CO2 in [Choline][Pro]/PEG200 at different pressures from 0 to 1.1 bar was also measured, and the enthalpy and entropy of solution of CO2 were calculated from the solubility data. At all the conditions, the enthalpy and entropy of solution were large negative values, indicating that the absorption process is exothermic.

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.

Transformation of Atmospheric CO2 Catalyzed by Protic Ionic Liquids: Efficient Synthesis of 2‐Oxazolidinones

Protic ionic liquids (PILs), such as 1,8-diazabicyclo[5.4.0]-7-undecenium 2-methylimidazolide [DBUH][MIm], can catalyze the reaction of atmospheric CO2 with a broad range of propargylic amines to form the corresponding 2-oxazolidinones. The products are formed in high yields under mild, metal-free conditions. The cheaper and greener PILs can be easily recycled and reused at least five times without a decrease in the catalytic activity and selectivity. A reaction mechanism was proposed on the basis of a detailed DFT study which indicates that both the cation and anion of the PIL play key synergistic roles in accelerating the reaction.

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.

Immobilization of Pd nanoparticles with functional ionic liquid grafted onto cross-linked polymer for solvent-free Heck reaction

1-Aminoethyl-3-vinylimidazolium bromide ([VAIM]Br) grafted on the cross-linked polymer polydivinylbenzene (PDVB) was synthesized. The copolymers were used as a support to immobilize palladium nanoparticles. The catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG) analysis, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of the copolymer-supported Pd nanoparticles for the Heck arylation of olefins with different aryl iodides was studied under solvent-free conditions. The results demonstrated that the catalyst was very active and stable under solvent-free conditions, and could be reused after simple separation. The reason for the high activity and stability of the catalyst is discussed.

Efficient synthesis of quinazoline-2,4(1H,3H)-diones from CO2 using ionic liquids as a dual solvent–catalyst at atmospheric pressure

The highly efficient transformation of CO2 into value-added chemicals is an interesting topic in green chemistry. In this work, we studied the synthesis of quinazoline-2,4(1H,3H)-diones from CO2 and 2-aminobenzonitriles in a series of ionic liquids (ILs). It was found that 1-butyl-3-methylimidazolium acetate ([Bmim]Ac), a simple and easily prepared IL, could act as both solvent and catalyst, the reactions could be carried out very efficiently at atmospheric pressure of CO2, and a high yield of the products was obtained. Further study indicated that the IL was also very efficient for converting other 2-aminobenzonitriles into their corresponding quinazoline-2,4(1H,3H)-diones in high yields at atmospheric pressure. Moreover, the separation of the products from the IL was very easy, and the IL could be reused at least five times without considerable loss in catalytic activity.