Weize Wu

Preparation of carbon-encapsulated iron carbide nanoparticles by an explosion method

Abstract Fe7C3 nanocrystals encapsulated in carbon nanoparticles, with sizes ranging from 10 to 40 nm, were synthesized via the explosion of a hybrid xerogel containing oxidized pitch and iron nitrate. Explosion of the hybrid xerogel was induced by heat treatment. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) were employed to determine the structure of the nanoparticles in the explosion product. The results show that the Fe7C3 nanocrystals are nested inside amorphous carbon shells that protect them from oxidation by air.

Preparation of room-temperature ionic liquids by neutralization of 1,1,3,3-tetramethylguanidine with acids and their use as media for mannich reaction

Abstract New room‐temperature ionic liquids (ILs) were prepared by neutralization of 1,1,3,3‐tetramethylguanidine with different acids under ambient condition. The density, viscosity, decomposition temperature, electronic conductivity, and miscibility with some commonly used solvents were determined. As an example of the applications of the new ILs, the reaction of benzaldehyde, aniline, and acetophenone was carried out in the ILs. The ILs are easily prepared in large scale.

A green and effective method to synthesize ionic liquids: supercritical CO2 route

Many room temperature ionic liquids (ILs) are nonvolatile solvents which have huge potential applications in various chemical processes. However, the synthesis of ILs usually uses different kinds of volatile organic solvents in the reaction and subsequent separation process. In this work, supercritical (sc) CO2, an environmentally benign solvent, has been utilized as the medium to synthesize ILs, 1-butyl-3-methylimidazolium bromide ([bmim]Br) and 1,3-dimethylimidazolium trifluoromethanesulfonate ([Me2Im]TfO). The results show that ILs can be synthesized in scCO2 with 100% yield and the excess reactants added can be extracted in situ by scCO2 without any cross-contamination. The whole process is green and very effective.

Hydrogenation of olefins using ligand-stabilized palladium nanoparticles in an ionic liquid

Phenanthroline (Phen) ligand-protected palladium nanoparticles in ionic liquid (IL) 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) are very active and selective for the hydrogenation of olefins, and the nanoparticles/IL system can be reused many times without reducing the activity.

A study of tri-phasic behavior of ionic liquid–methanol–CO2 systems at elevated pressures

The phase behavior of CO2–methanol–1-n-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF6]) system under different conditions has been studied by a static method. The results demonstrate that at 40.0 °C there can exist three phases (IL-rich phase, the methanol-rich phase, CO2-rich phase) in the pressure range from 6.95 to 8.21 MPa when the concentration of the IL is low. In the high IL concentration region, however, there is only one liquid phase in the entire pressure range. In the three-phase region, the difference of the concentrations of the IL in the two liquid phases becomes larger and larger with increasing pressure. The results also show that the three-phase region exists only in the temperature range from 35 to 44.5 °C at 7.6 MPa. In the three-phase region IL concentration in the IL-rich phase decreases with increasing temperature, while that in the methanol-rich phase increases as temperature rises, and the difference of IL concentration in the two liquid phases is sensitive to temperature. On the basis of phase equilibrium data the distribution coefficients of [bmim][PF6] in the two liquid phases are calculated and discussed.

Solubility of room-temperature ionic liquid in supercritical CO2 with and without organic compounds

Ionic liquid can dramatically dissolve in supercritical (sc) CO2 with polar organic compounds (ethanol, acetone) especially as the concentration of the compounds in scCO2 exceeds 10 mol%, while the effect of a nonpolar organic compound (n-hexane) in scCO2 on the solubility is very limited even when its concentration is as high as 30 mol%.

Replication of biological organizations through a supercritical fluid route

A novel and simple method to replicate biological organizations (cotton and pollen grains) with high precision was proposed, in which the precursor dissolved in supercritical CO2 reacted with the surface active groups and adsorbed surface water on biological templates, followed by in situ SCF extraction of the byproducts and unreacted precursor, resulting in inorganic replicas faithfully copying both the macro- and microstructures of the biotemplates.

Effect of compressed CO2 on the properties of AOT reverse micelles studied by spectroscopy and phase behavior

Combination of reverse micellar solutions and supercritical or compressed carbon dioxide (CO2) is a new and interesting topic. This work conducted the first study on the effect of compressed CO2 on the micro-properties (e.g., micropolarity, ionic strength, pH) of the sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles in isooctane by phase behavior measurement, Fourier transform infrared and UV–vis spectroscopic techniques. The results show that CO2 can dissolve in both the organic-continuous phase and the water cores of the reverse micelles. The properties of the reverse micelles can be tuned continuously by changing the pressure of CO2 because the solubility of CO2 in the solution and in the water cores depends on the pressure. CO2 in the water cores can be ionized to produce HCO3−1 and H+. The micropolarity and ionic strength of the water cores increase with the pressure of CO2. Accordingly, the pH is reduced as the pressure and water-to-surfactant molar ratio (w0) are increased.

Effect of cosolvent on the phase behavior of non-fluorous Ls-54 surfactant in supercritical CO2

Abstract The effect of 1-propanol, n -pentanol, n -heptanol, and benzyl alcohol on the phase behavior of CO 2 /Ls-54 system has been investigated. The results indicate that the alkyl chain alcohols can reduce the cloud point pressure (CPP) considerably, and the smaller alcohols are more effective. However, addition of benzyl alcohol leads to increase in CPP. In addition, the phase behavior study of Ls-54 surfactant in supercritical (SC) CO 2 with different n -heptanol concentration was also carried out. The results showed that the CPP increases with increasing temperature and decreases with increasing n -heptanol concentration.

Detonation chemistry of a CHNO explosive: catalytic assembling of carbon nanotubes at low pressure and temperature state.

The detonation of a CHNO explosive was used for the first time to synthesize carbon nanotubes effectively at low pressure and temperature by introducing a cobalt catalyst and/or paraffin into the detonation system.