This Review chronicles the progress made in the field of small fluorocarbon synthesis since their invention in the early 1930s by Thomas Midgley, Jr., and his coworkers, with special focus on their...

Fluorocarbon Refrigerants and their Syntheses: Past to Present.

Efficient synthesis of dimethyl carbonate via transesterification of ethylene carbonate with methanol over binary zinc-yttrium oxides

In order to cope with the ever-increasing operating temperature of aero gas turbines, new thermal barrier coatings are being investigated. Among the different solutions, erbia-yttria co-doped zirconia coatings made by electron-beam physical vapour deposition (EB-PVD) show promising results in terms of thermal insulation enhancement. Annealing of these coatings was performed at 1100 °C in air in order to investigate their stability in comparison with that of standard 8 wt% yttria-stabilized zirconia (8YSZ). Their thermal transport properties were measured using the laser-flash technique. The results show that the as-deposited co-doped coatings offered lower heat conduction than the standard ones in the studied temperature range (from room temperature to 1100 °C). However, the microstructural and phase transformations of the co-doped coatings after annealing were significantly greater than those of the standard coatings, hence strongly modifying their thermal insulation potential.

/pdf/phase-stability-and-thermal-insulation-of-ysz-and-erbia-1fzndfbgb3.pdf

Phase stability and thermal insulation of YSZ and erbia-yttria co-doped zirconia EB-PVD thermal barrier coating systems

Catalytic dehydrofluorination of 1,1,1,3,3-pentafluoropropane to 1,3,3,3-tetrafluoropropene over fluorinated NiO/Cr 2 O 3 catalysts

Magnesium oxide (MgO), as an exceptionally important inorganic material, has been widely studied in view of its unique surface properties, but the correlation between its surface structure and physicochemical performance is still scarce. Here we report the evolution of the surface structure and physicochemical properties of trapezoid-like MgO microparticles with calcination temperature by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. The results demonstrated that along with the surface change of MgO from a smooth appearance to the structure composed of nanoparticles, its corresponding crystal structure evolved from mesocrystal to polycrystal, then to pseudomorph, and finally to cubic single crystal with the increase of calcination temperature ranging from 400 °C to 1000 °C. It also illustrated that the electrochemical capability of MgO was highly dependent on its crystal structure, whereas its catalytic activity had a good correlation with its textural properties (e.g., surface area and porosity) although the reaction selectivity was related to the calcination temperature. This work highlights the vital role of calcination temperature in determining the surface structure and physicochemical properties of the inorganic material MgO, which in turn will tailor its overall performance in the final applications.

Calcination temperature-dependent surface structure and physicochemical properties of magnesium oxide

Effect of calcination temperature on CrOx–Y2O3 catalysts for fluorination of 2-chloro-1,1,1-trifluoroethane to 1,1,1,2-tetrafluoroethane

Er-Y-codoped ZrO2 mixed oxides with monoclinic, tetragonal and cubic structures were prepared by a sol-gel method. The crystal structure of ZrO2 matrix and the effect of the ZrO2 phases on the fluorescence properties of Er3+ were studied using Raman spectroscopy. The results indicated that the fluorescence properties of Er3+ depend on its local ZrO2 crystal structures. As ZrO2 matrix transferred from monoclinic to tetragonal and cubic phase, the Raman and fluorescence bands of Er3+ decreased in intensities and tended to form a single peak. With 632.8 nm excitation, the bands between 640 and 680 nm were attributed to the fluorescence of Er3+ in the ZrO2 environment. However, only the fluorescence was observed and no Raman spectra were seen under 514.5 nm excitation, while only Raman spectra were observed under 325 nm excitation. UV Raman spectroscopy was found to be more sensitive in the surface region while the information provided by XRD mainly came from the bulk. The phase with lower symmetry forms more easily on the surface than in the bulk.

Raman Spectrum of Er-Y-codoped ZrO2 and Fluorescence Properties of Er3+

The fluorination of 2-chloro-1,1,1-trifluorocthane (CF 3 CH 2 Cl) to synthesize 1,1,1,2-tetrafluoroethane (CF 3 CH 2 F) has been carried out on various CrO x -Y 2 O 3 catalysts with different Cr loadings. The effect ofCr loading on the catalyst composition and structure has been investigated. X-ray diffraction and Raman results indicate that the CrO x species with high oxidation state (Cr(VI)) are well dispersed on the catalyst surface when the Cr loading was lower than 19.5 %. With increase in Cr loading, crystalline Cr 2 O 3 and polymeric chromate are formed, which inhibit pre-fluorination of the catalysts. The catalysts are stable under the reaction conditions and the catalytic activity is strongly dependant on the pre-fluorinated CrO x content. The highest activity is obtained on a pre-fluorinated catalyst with a Cr loading of 19.5, with a 19 % CF 3 CH 2 Cl conversion at 320 °C, corresponding to a formation rate of 2.03 mmol h -1 g -1 cat , which is 3-fold higher than the best result obtained over a Cr/MgF 2 catalyst (0.68 mmol h -1 g -1 cat ) under similar conditions. The Cr-Al 2 O 3 catalyst has also been prepared and tested for the probe reaction in this study. The activity is lower as compared to that of the Cr-Y 2 O 3 catalyst with the same Cr content. The higher activity of Cr-Y 2 O 3 catalyst may be due to the higher degree of dispersion of the Cr(VI) species on the Y 2 O 3 support than on other supports. It is also found that the CrF x , CrO x F y or Cr(OH) x F y phases originating from higher oxidation state Cr(VI) species are the active sites for the fluorination reaction.

http://nopr.niscair.res.in/bitstream/123456789/3899/1/IJCA%2048A%284%29%20489-497.pdf

Characterization of CrO x -Y 2 O 3 catalysts for fluorination of 2-chloro-1,1,1-trifluoroethane

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Effect of calcination temperature on CrOx–Y2O3 catalysts for fluorination of 2-chloro-1,1,1-trifluoroethane to 1,1,1,2-tetrafluoroethane

Raman Spectrum of Er-Y-codoped ZrO2 and Fluorescence Properties of Er3+

Characterization of CrO x -Y 2 O 3 catalysts for fluorination of 2-chloro-1,1,1-trifluoroethane