Deep Oxidation of Fluorinated Hydrocarbons in Molten Catalysts

The oxidation of fluorine-containing organic substances: fluorocarbon liquid M-1, fluorinated alcohol H(CF2)8CH2OH, and powder polytetrafluoroethylene with air has been studied in melts: NaOH; 43 mol.% LiCl В - 33 mol.% NaCl - 24 mol.% KCl (eutectic mixture); (LiCl-NaCl-KCl)eutec. + 10 mass.% V2O5; (LiCl-NaCl-KCl) eutec. + 15 mass.% V2O5; 56 mol.% Na2CO3 - 44 mol.% K2CO3 (eutectic), (Na2CO3 K2CO3)eutect. + 15 mass.% V2O5, and K3V5O14. The compositions of the melts have been examined by GC, DTA, chemical analysis and XRD, and they have been shown to change during the reaction, depending on the composition and partial pressure of the gaseous products over the melt surface. The alkali metal chloride melt containing 15 mass.% V2O5 has been found to be most stable to the action of fluorine compounds. Possibility of deep oxidation of fluorine-containing organic substances in melts based on hydroxides, carbonates and chlorides of alkali metals doped with oxides of vanadium has been proved. The process of deep oxidation of fluorinated hydrocarbons is accompanied by formation of an equilibrium mixture containing hydroxides, carbonates, chlorides and fluorides of alkali metals, as well as their vanadates, if V2O5 additive is used. The relative amounts of these substances in molten systems are determined by the partial pressure of oxygen, CO2 and water vapor

Catalytic Oxidation of Volatile Organic Compounds in Industrial Off-Gases

Processes and apparatuses for catalytic oxidation of VOCs in industrial off-gases are described, including steady state and unsteady state processes, a combined adsorption-catalytic process and an advanced method of ozone induced oxidation for low concentrated exhausts. On the basis of research and development works a series of catalytic incinerators, operating in steady state and unsteady state mode, of various capacity were designed, constructed and tested in the purification of ventilation air and off-gases from VOCs. The principles of operation of different types of catalytic incinerators and possible areas of application are discussed. For VOC concentrations 150-1000 mg/m3 unsteady state catalytic incinerators of KART type should be used, for concentrations 1000-3000 mg/m3 steady state KROT apparatuses are recommended, and for concentrations over 3000 mg/m3 up to 7000 mg/m3 installations TKM-250. It is shown that for the purification of low concentrated gases with the content of organic vapors below 150 mg/m3 adsorptioncatalytic method or catalytic oxidation with ozone in the installation OKA-3000 are most effective. Main kinetic dependencies of the ozone induced oxidation of toluene and acetone over copper oxide catalyst are given and discussed. It is shown that the efficiency of this method of VOCs removal is based on low operation temperature 313-343 K, by contrast to conventional catalytic incineration by air requiring preliminary heating of the gases to 523-573 K. A special consideration is given to adsorptive damping as an efficient method for leveling the VOCs concentrations in the real industrial exhausts directed to the catalytic treatment. The use of adsorptive dampers filled with carbon allows elimination of large deviations of pollutant concentrations in the gas entering the catalyst bed, thus increasing the VOCs removal efficiency from average values. For calculations of adsorptive dampers, an equation describing the profiles of VOC concentrations in gas phase along the length of the adsorbate bed in the damper was derived

Control of Ni/Ce1-xMxOy catalyst properties via the selection of dopant M = Gd, La, Mg Part 1. Physicochemical characteristics

To elucidate the role of support composition in autothermal reforming of ethanol (ATR of C2H5OH), a series of Ni catalysts (Ni content 2–15 wt.%) supported on different ceria-based oxides (Ce1-xGdxOy, Ce1-xLaxOy and Ce1-xMgxOy; x = 0.1–0.9) were prepared. The synthetized materials were tested in ATR of ethanol at 200–700 °C. It was established that supports themselves show catalytic activity in ATR of C2H5OH and provide 10–15% yield of H2 at 700 °C. Upon the increase of Ni content from 2 to 15 wt.% the temperature of 100% ethanol conversion decreases from 700 tо 300 °С, hydrogen yield increases from 25 to 60%, the inhibition of С2-С3 by-products formation, as well as the promotion of decomposition of acetaldehyde occur. The enhancement of catalyst performance in ATR of C2H5OH has been observed in the next series of supports: Ce1-xMgxOy < Ce1-xGdxOy < Ce1-xLaxOy and with a decrease of x to an optimal value that correlates with the improvement of Ni active component reducibility. At 600 °C on 10Ni/Ce0.8La0.2O1.9 catalyst the H2 yield of 50% was achieved at C2H5OH conversion of 100%. Stable and high performance of developed catalysts in ATR of C2H5OH indicates the promise of their use in the production of hydrogen

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%

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%

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

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