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  • Nanocomposites of ionic liquids confined in mesoporous silica gels: preparation, characterization and performance
  • 更新时间:2014-04-10;信息类型:SCI论文
  • A series of nanocomposites of ionic liquids (ILs) were prepared via a modified sol–gel method. The ILs were physically confined in mesoporous silica gels with 5–40% content. ILs from imidazolium, thiophenium and ammonium with different anions were prepared and used. Characterization using the Brunauer–Emmett–Teller (BET) method, Fourier transform infrared (FT-IR) spectroscopy, temperature-programmed desorption (TPD), differential scanning calorimetry (DSC), inverse gas chromatography (IGC), temperature-controlled Raman and fluorescence emission spectroscopies was conducted to explore any confinement effects. BET results showed that, depending on the ILs and their contents, the average pore diameter of the pure silica gel was 3–12 nm after the confined ILs were removed completely. It was suggested that ILs aggregated on the nanoscale in the mesoporous silica gel. In comparison with bulk ILs and ILs coated onto silica gels (IL/sg), IL nanocomposites (IL–sg) displayed remarkably low specific heat capacities (Cp was in the range 0.3–1.2 Jg-1K-1), disordered vibrational conformations (without phase transitions in the range 100–200 1C), greater interactions with hydrocarbon solutes (adsorption capacities of 0.3–0.4 g per 100 g for confined ILs with CO2 gas), and greatly enhanced fluorescence emission (up to 200 times stronger than bulk ILs). Furthermore, Based on the specific solubility of different compounds, the nanocomposites could also be applied to the separation of CO2 from CO2/N2 mixtures and thiophene from thiophene/octane mixtures.
  • 链接地址:http://www.ionicliquid.org/download/article/2014-04-10/123.html
  • Copper-Catalyzed N-Alkylation of Sulfonamides with Benzylic Alcohols: Catalysis and Mechanistic Studies
  • 更新时间:2014-04-10;信息类型:SCI论文
  • The N-alkylation of sulfonamides with alcohols is efficiently performed in the presence of easily available copper catalysts via hydrogen borrowing methodology. Applying a copper acetate/potassium carbonate system the reaction of sulfon-ACHTUNGTRENUNGamides and alcohols gave the corresponding secondary amines in excellent yield. In situ HR-MS analysis indicated that bissulfonylated amines are formed under air atmosphere, which act as self-stabilizing ligands for the catalytic system. UV-visible measurements suggest the interaction between the copper centre and the bissulfonylated amine. Reactions of benzyl alcohol-d7 with p-toluenesulfonamide, Nbenzyl-p-toluenesulfonamide or N-benzylidenetolu-ACHTUNGTRENUNGenesulfonamide revealed that the reaction proceeds via a transfer hydrogenation mechanism and the whole process is micro-reversible. Competitive reactions of benzyl alcohol and benzyl alcohol-d7 with ptoluenesulfonamide revealed a kinetic isotope effect (kH/kD) of 3.287 (0.192) for the dehydrogenation of benzyl alcohol and 0.611 (0.033) for the hydrogenation of the N-benzylidene-p-toluACHTUNGTRENUNGenesulfonamide intermediate, which suggests that dehydrogenation of the alcohol is the rate-determining step.
  • 链接地址:http://www.ionicliquid.org/download/article/2014-04-10/114.html
  • Ferric hydroxide supported gold subnano clusters or quantum dots: enhanced catalytic performance in chemoselective hydrogenation
  • 更新时间:2014-04-09;信息类型:SCI论文
  • An attempt to prepare ferric hydroxide supported Au subnano clusters via modified co-precipitation without any calcination was made. High resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the structure and chemical states of these catalysts. No Au species could be observed in the HRTEM image nor from the XRD pattern, suggesting that the sizes of the Au species in and on the ferric hydroxide support were less than or around 1 nm. Chemoselective hydrogenation of aromatic nitro compounds and a,b-unsaturated aldehydes was selected as a probe reaction to examine the catalytic properties of this catalyst. Under the same reaction conditions, such as 100 ◦C and1MPaH2 in the hydrogenation of aromatic nitro compounds, a 96–99% conversion (except for 4-nitrobenzonitrile) with 99% selectivity was obtained over the ferric hydroxide supported Au catalyst, and the TOF values were 2–6 times higher than that of the corresponding ferric oxide supported catalyst with 3–5 nm size Au particles. For further evaluation of this Au catalyst in the hydrogenation of citral and cinnamaldehyde, selectivity towards unsaturated alcohols was 2–20 times higher than that of the corresponding ferric oxide Au catalyst.
  • 链接地址:http://www.ionicliquid.org/download/article/2014-04-09/109.html
  • Low-temperature prepared highly effective ferric hydroxide supported gold catalysts for carbon monoxide selective oxidation in the presence of hydrogen
  • 更新时间:2014-04-09;信息类型:SCI论文
  • Ferric hydroxide supported Au catalysts prepared with co-precipitation method at room temperature without any heat treatment hereafter exhibited high catalytic activity and selectivity for CO oxidation in air and CO selective oxidation in the presence of H2. With calcination temperature rising, both activity and selectivity decreased. X-ray Photoelectron Spectra (XPS) indicated that Au existed as Au0 and Au+ in the catalyst without heat treatment and even after being calcined at 200 ℃, while after being calcined at 400 ℃, Au existed as Au0 completely. X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopic (HRTEM) investigations indicated that both the supports and Au species were highly dispersed as nano or sub-nano particles even after being calcined at 200 ℃, but after being calcined at 400 ℃ the supports transformed to crystal Fe2O3 with typical diameter of 30 nm and Au species aggregated to nano-particles with typical diameter of 2–4 nm. HRTEM investigations also suggested that the supports calcined at 200 ℃ were composed of amorphous ferric hydroxide and crystal ferric oxide. Results of computer simulation (CS) showed that O2 was adsorbed on Au crystal cell and then were activated, which should be the key factor for the subsequent reaction. It also suggested that O2 species were more easily adsorbed on Au+ than on Au0, indicating that higher positive charge of the Au species possessed the higher activity for CO oxidation.
  • 链接地址:http://www.ionicliquid.org/download/article/2014-04-09/108.html
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