Comparative study between gas phase and liquid phase for the production of DMC from methanol and CO_2

Direct synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide over Co1.5PW12O40 in liquid and in gas phase is investigated. The synthesized catalyst has been characterized by means of FTIR and XRD. Liquid phase experiment results showed that high pressures are favorable for the synthesis of DMC. However, DMC formation is limited by the reaction with co-produced water. DMC selectivity is more strongly dependent on the temperature than on the pressure of CO2. As for the reactions in gas phase, it has been found that both CH3OH conversion and DMC selectivity decreased with increasing temperature, owing to the decomposition of DMC at high temperatures. High temperatures and more amount of Co1.5PW12O40 catalyst favor the formation of dimethoxymethane （DMM） and methyl formate （MF）.

Carbon Nanofibers Containing Ag/TiO₂Composites as a Preliminary Stage for CDI Technology

Silver/titanium dioxide composite nanoparticles imbedded in polyacrylonitrile (PAN) nanofibers and converted into carbon nanofibers by stabilization and calcination was obtained and tested for capacitive deionization technology. First, the silver ions were converted to metallic silver nanoparticles, through reduction of silver nitrate with dilute solution of PAN. Second, the TiO2 precursor (Titanium Isopropoxide) was added to the solution to form Ag/TiO2 composites imbedded in the PAN polymer solution. Last step involves electrospinning of viscous PAN solution containing silver/TiO2 nanoparticles, thus obtaining PAN nanofibers containing silver/TiO2 nanoparticles. Scanning electron microscopy (SEM) revealed that the diameter of the nanofibers ranged between 50 and 300 nm. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) showed silver/TiO2 nanoparticles dispersed on the surface of the carbon nanofibers. The obtained fiber was fully characterized by measuring and comparing the FTIR spectra and thermogravimetric analysis (TGA) diagrams of PAN nanofiber with and without imbedded nanoparticles, in order to show the effect of silver/TiO2 nanoparticles on the electrospun fiber properties.

Influences of Silver-Doping on the Crystal Structure, Morphology and Photocatalytic Activity of TiO₂Nanofibers

Doping of titanium dioxide nanofibers by silver nanoparticles revealed distinct improvement in the photocatalytic activity;however other influences have not been investigated. In this work, effect of sliver-doping on the crystal structure, the nanofibrous morphology as well as the photocatalytic activity of titanium oxide nanofibers has been studied. Silver-doped TiO2 nanofibers having different silver contents were prepared by calcination of electrospun nanofiber mats consisting of silver nitrate, titanium isopropoxide and poly(vinyl acetate) at 600℃. The results affirmed formation of silver-doped TiO2 nanofibers composed of anatase and rutile when the silver nitrate content in the original electrospun solution was more than 3 wt%. The rutile phase content was directly proportional with the AgNO3 concentration in the electrospun solution. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that increase the silver content strongly enhances the dye oxidation process.

N-methyl-2-pyrrolidonium-based Br?nsted-Lewis acidic ionic liquids as catalysts for the hydrolysis of cellulose

We experimentally studied the catalytic performances of a series of Br?nsted-Lewis acidic N-methyl-2-pyrrolidonium metal chlorides([Hnmp]Cl/MCl_x, where M=Fe, Zn, Al, or Cu) for the hydrolysis of microcrystalline cellulose(MCC) and cotton to produce reducing sugar. A variety of factors, such as temperature, time, ionic liquid(IL) species, IL dosage, and the concentration of the metal chloride were investigated. [Hnmp]Cl/FeCl_3 presented the best hydrolysis performance, affording a 98.8% yield of total reducing sugar from MCC(1 h, 100 °C, 0.1 g MCC, 0.2 g acidic IL, 2.0 g [Bmim]Cl as solvent), which is better than or comparable to results previously obtained with other –SO_3H functionalized acidic ILs. The hydrolysis performances of [Hnmp]Cl/MClx were rationalized using density functional theory calculations, which indicated that interactions between the metal chlorides and the cellulose, including charge-transfer interactions are important in the hydrolysis of cellulose and degradation of glucose. This work shows that Br?nsted-Lewis acidic ILs are potential catalysts for the hydrolysis of cellulose to produce sugar.

In vitro evaluation of electrospun gelatin-glutaraldehyde nanofibers

The gelatin-glutaraldehyde （gelatin-GA） nanofibers were electrospun in order to overcome the defects of ex-situ crosslinking process such as complex process, destruction of fiber morphology and decrease of porosity. The morphological structure, porosity, thermal property, moisture absorption and moisture retention performance, hydrolytic resistance, mechanical property and biocompatibiUty of nanofiber scaffolds were tested and characterized. The gelatin-GA nanofiber has nice uniform diameter and more than 80% porosity. The hydrolytic resistance and mechanical property of the gelatin-GA nanofiber scaffolds are greatly improved compared with that of gelatin nanofibers. The contact angle, moisture absorption, hydrolysis resistance, thermal resistance and mechanical property of gelatin-GA nanofiber scaffolds could be adjustable by varying the gelatin solution concentration and GA content. The gelatin- GA nanofibers had excellent properties, which are expected to be an ideal scaffold for biomedical and tissue engineering applications.