Congyi Wu

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.

Highly efficient hydrogenation of carbon dioxide to methyl formate over supported gold catalysts

Transformation of carbon dioxide (CO2) into valuable chemicals is an interesting topic in green chemistry. Hydrogenation of CO2 to methyl formate (MF) in the presence of methanol is an important reaction. In this work, Au nanocatalysts immobilized on different supports were prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectrometry (XPS). The catalytic performances of the catalysts for the reaction were studied. It was demonstrated that the Au/ZrO2, Au/CeO2 and Au/TiO2 were very active and selective for the reaction in the absence of any basic additives. The Au/ZrO2 was more active than Au/CeO2 and Au/TiO2 if the sizes of Au particles on the supports were similar. Moreover, for the Au/ZrO2 catalysts, Au particles with smaller size had higher activity. The possible mechanism of the catalytic reaction was proposed.

A strategy to overcome the thermodynamic limitation in CO2 conversion using ionic liquids and urea

Enhancing the equilibrium conversion of thermodynamically unfavorable reactions is a very interesting and challenging topic for chemists. The unique properties of ionic liquids (ILs) provide new opportunities to solve this problem. Herein a strategy is proposed to circumvent the thermodynamic limitation of chemical reactions using the designable and non-volatile nature of ILs. In this approach a reactant first reacts with a functional IL to form a high energy IL intermediate, which can further react with other reactants to yield products and regenerate the IL. To verify the feasibility of this strategy, the syntheses of dimethyl carbonate (DMC) and methyl formate (MF) via urea, which are very important reactions used to convert CO2 but are thermodynamically unfavorable, were conducted with the aid of a diol IL. It was found that the equilibrium yields of DMC and MF obtained by this methodology could be 64 times and 9 times higher, respectively, than those of the conventional methods.

Laminar Plasma Jets: Generation, Characterization, and Applications for Materials Surface Processing

Nontransferred direct current (dc) laminar plasma jets of pure argon were generated at atmospheric pressure, with a generator having an interelectrode insert. Associated with the experimental investigation, similarity theory was adopted to examine the arc voltage characteristics, thermal efficiency, and jet length change of the laminar plasma. Jet flow temperature and velocity were evaluated by various methods. The jet shows good stability, reproducibility, and regular flow field change as functions of generating parameters. Applications of laminar plasma jets for ZrO2 ceramics spray coating and remelt strengthening of metal surface were attempted. The results indicated favorite process efficiency and controllability of the laminar plasma heating.

MoP Nanoparticles Supported on Indium‐Doped Porous Carbon: Outstanding Catalysts for Highly Efficient CO2 Electroreduction

Electrochemical reduction of CO2 into value-added product is an interesting area. MoP nanoparticles supported on porous carbon were synthesized using metal-organic frameworks as the carbon precursor, and initial work on CO2 electroreduction using the MoP-based catalyst were carried out. It was discovered that MoP nanoparticles supported on In-doped porous carbon had outstanding performance for CO2 reduction to formic acid. The Faradaic efficiency and current density could reach 96.5 % and 43.8 mA cm-2 , respectively, when using ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as the supporting electrolyte. The current density is higher than those reported up to date with very high Faradaic efficiency. The MoP nanoparticles and the doped In2 O3 cooperated very well in catalyzing the CO2 electroreduction.

Efficient Hydrogenation of CO2 to Methanol over Supported Subnanometer Gold Catalysts at Low Temperature

Direct hydrogenation of CO2 to methanol under milder conditions is of great importance. The catalytic performances of Au particles with different sizes on various supports for this reaction were studied. It was demonstrated that catalytic properties of the catalysts depended both on size of Au particles and the composition of the supports. Au/ZrO2 with subnanometer Au particles (1.6 nm) had unprecedented high catalytic activity and excellent selectivity for the reaction, and methanol could be obtained even at 140 °C, which is obviously lower than those reported before. The outstanding performance of the Au/ZrO2 with subnanometer Au particles resulted from both the very small size of the Au particles and appropriate coupling between the Au particles and the support.

Poly(ethylene glycol) based bis-diol as a functional medium for highly efficient conversion of urea and methanol to dimethyl carbonate

Dimethyl carbonate (DMC) is a useful chemical and can substitute some toxic substances. The synthesis of DMC from methanol and urea is an attractive route, but is a thermodynamically unfavourable reaction. Enhancing the equilibrium conversion of the reaction is an intereting topic. In this study, we demonstrate that poly(ethylene glycol) diglyceryl ether (PEGDE, a poly(ethylylene glycol) based bis-diol), which is a non-toxic and cheap polymer, can be used as a functional medium for the synthesis of DMC from methanol and urea using ZnO as the catalyst. In the PEGDE/ZnO catalytic system, PEGDE reacted with urea to form poly(ethylene glycol) di(2,3-carbonate glyceryl) ether (PEGDC), and the reaction equilibrium was shifted by sweeping away the generated ammonia. Then, DMC was produced after methanol was added and PEGDE was regenerated and the PEGDE/ZnO catalytic system could be reused directly. It was shown that a very high equilibrium yield could be achieved.

Microwave assisted synthesis of glycerol carbonate from glycerol and urea

Abstract The transformation of glycerol into value-added chemicals is an interesting topic in Green Chemistry. The glycerolysis of urea into glycerol carbonate is an important route of glycerol transformation. In this work, the synthesis of glycerol carbonate from glycerol and urea was performed under microwave irradiation and solvent free conditions. The catalytic properties of ZnSO4, ZnCl2, CuSO4 and MgSO4 were tested and ZnSO4 showed the best performance. The effects of catalyst amount, temperature, reaction time, microwave power, molar ratio of urea to glycerol on the reaction were studied using ZnSO4 as the catalyst. It was demonstrated that microwave irradiation could promote the reaction effectively, and the yield of desired product glycerol carbonate could reach 93.7%.

Effects of anode temperature on the arc volt–ampere characteristics and ejected plume property of a low-power supersonic plasma

Low-power plasma generators with two kinds of hot anode/nozzle structures, one with a natural radiation-cooled nozzle and the other with a regeneratively cooled nozzle, were designed to investigate the dependence of the volt?ampere characteristics on the anode temperature. Pure argon, nitrogen or hydrogen gas was used as the plasma working gas at input powers from 130 to 1200?W in a plenum chamber kept at a pressure of below 20?Pa. Variations of the arc voltage with changes in arc current, gas flow rate and firing time (anode temperature) were examined, and the effects of the arc volt?ampere characteristics on the properties of the ejected plasma flow from the nozzle exit are discussed with respect to the evaluation of the average plume temperature and flow velocity. Results show that there are definitely non-negligible effects of anode temperature on these characteristics.