Design of highly efficient catalyst for rational way of direct conversion of methane

Effects of composition and preparation method of MnNaW/SiO2 and LaSr/CaO catalysts on their physical-chemical properties and performance in oxidative coupling of methane (OCM) have been studied. For MnNaW/SiO2 catalysts the synthesis method and type of SiO2 have a significant effect on the texture, while the Na/W ratio determines the phase composition. The variation of preparation method and temperature of catalyst calcination allows regulation of the metal surface concentration and mode of metal distribution across the SiO2 support. For LaSr/CaO catalysts the synthesis method determines the specific surface area, surface and phase composition. Correlations between catalyst performance, preparation method and state of the catalyst were established. The rational preparation procedure and perspective composition of OCM catalyst have been developed. The 20La/CaO catalysts prepared by citrate sol-gel method were shown to provide ~20% C2 yield and ~40% methane conversion at 800 ºC

Design of Pt-Sn catalysts on mesoporous titania films for microreactor application

A new generation of nanostructured Pt–Sn/TiO2 catalytic thin films has been developed by deposition of Pt–Sn mixed-metal precursors from organic solvents on mesoporous TiO2/Ti films with a thickness of 200–300 nm. The titania sol was obtained by templating a TiO2 precursor with Pluronic F127 surfactant. The films were prepared on Ti substrates by spin-coating. The influence of the F127/Ti ratio in the range between 0.006 and 0.050, the pH of the titania sol between 1.5 and 2.0, and the aging time between 8 and 240 h on the morphology and porous structure of titania films was investigated. A TiO2 film with the highest degree of the long-order structure was obtained at a surfactant/Ti molar ratio of 0.009, a pH of 1.5, and an aging time of 24 h. This film has a hexagonal pore structure with a mean pore size of 3.5 nm and a porosity of 25%. A powder titania support with a similar chemical composition and morphology was also produced and used for optimization of an active component deposition. The Pt–Sn carbonyl [Pt3(CO)3(SnCl3)2(SnCl2·H2O)]n-2n clusters were synthesized separately from monometallic precursors. They were loaded onto the TiO2 supports by impregnation or adsorption. The adsorption of the Pt–Sn precursor for 24 h from an ethanol solution with concentrations of Pt and Sn of 2.0 and 1.2 mg/ml, respectively, followed by a vacuum treatment at 463 K, resulted in Pt–Sn nanoparticles embedded in the mesoporous titania network. An average size of bimetallic nanoparticles was 1.5–2 nm with a narrow particle size distribution. A reaction rate in terms of TOF between 0.2 and 3.3 min-1 was observed in the hydrogenation of citral over the Pt–Sn/TiO2 catalysts. The selectivity to the unsaturated alcohols was as high as 90% at a citral conversion above 95%

Oxidation of organic compounds in a microstructured catalytic reactor

A microstructured catalytic reactor for the oxidation of organic compounds has been fabricated from aluminum alloy AlMgSiCu1 (6082 series, Al51st). The catalyst section was assembled of 63 microstructured plates with catalytic coating. In each plate of 416 µm thickness, 45 semi-cylindrical microchannels of 208 µm in radius with a distance in between of 150 µm were electrodischarge machined. A porous alumina layer of 29 ± 1 µm thickness was produced on the plates by anodic oxidation. The resulting coatings were impregnated with an aqueous solution of copper dichromate followed by drying and calcination at 450 °C to produce active catalysts. Kinetics of deep oxidation of organic compounds n-butane, ethanol, and isopropanol was studied in the reactor at 150–360 °C and of 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) at 200–375 °C. Intermediate reaction products in the reactions of alcohols and UDMH oxidation were identified. For UDMH, these are methane, dimethylamine, formaldehyde 1,1-dimethylhydrazone, and 1,2-dimethyldiazene. Nitrogen atoms from the UDMH and N-containing intermediates were shown to convert mainly to N2. Kinetic parameters of the reactions of n-butane and alcohols (rate constants and apparent activation energies) were calculated using kinetic modeling based on a modified method of quickest descent

Optimization of anodic oxidation and Cu-Cr oxide catalyst preparation on structured aluminum plates processed by electro discharge machining

This paper describes the optimization of three processes applied in fabrication of a microstructured reactor for complete oxidation of volatile organic compounds. The first process involves the optimization of the electro discharge machining (EDM) method to produce a set of microchannels with a high length to diameter ratio of 100, with a standard deviation from the average diameter below 0.2%, and with a surface roughness not higher than 2.0 µm. To satisfy these criteria, fabrication of microchannels must be carried out with two machining passes in the Al51st alloy. Then, the effect of several parameters on the anodization current efficiency with respect to oxide formation was studied. The best process conditions to get a 30 µm porous alumina layer in a 0.4 M oxalic acid electrolyte, were found to be a temperature of 1 °C, an anodic current density of 5 mA/cm2, and 23 h oxidation time. At last, the resulting coatings were impregnated with an aqueous solution of copper dichromate followed by drying and calcination at 450 °C to produce active catalysts. The effect of a copper dichromate concentration, number of impregnation cycles (1 or 2), and different after-treatments on catalytic activity and stability in complete oxidation of n-butane were studied. The catalytic activity of the obtained coatings is superior to that of alumina supported pelletized catalysts even at much lower loadings of active metals

Real time chemical imaging of a working catalytic membrane reactor during oxidative coupling of methane

We report the results from an operando XRD-CT study of a working catalytic membrane reactor for the oxidative coupling of methane. These results reveal the importance of the evolving solid state chemistry during catalytic reaction, particularly the chemical interaction between the catalyst and the oxygen transport membrane