Temperature-programmed reduction and oxidation of bimetallic Pd?Ni/Al2O3 catalysts

Temperature-programmed reduction and oxidation of bimetallic catalysts Pd–Ni/Al₂O₃ seem to indicate phase segregation of palladium and nickel oxides and alloying of palladium and nickel in the process of reduction of oxidized catalysts.

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- Pd–Ni/Al₂O₃ , .

     

Determination of metal dispersity of Pd/SiO2 catalysts by transmission electron microscopy and H2?O2 chemisorption

Dispersity of palladium for a series of Pd/SiO₂ catalysts has been determined by TEM and H₂–O₂ chemisorption. The mean crystallite dimensions obtained by these methods have been compared. Assuming O/Pd_s to be 0.6 for Pd crystallites larger than 9 nm, good agreement has been observed between the results of the two experimental methods.

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Pd/SiO₂ H₂–O₂. , . O/Pd_s0.6, Pd 9 , .

     

Temperature programmed reduction and oxidation of Ir/Al2O3 catalysts

3 % Ir/Al₂O₃ catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher T_ox) reducibility of the catalysts at low temperatures decreases.

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3% Ir/Al₂O₃ . ( ) .

     

Displacement of hydrogen from rhodium surface by carbon monoxide under conditions of pulsed-gas chromatography

Interaction of carbon monoxide with hydrogen on the surface of rhodium catalysts has been investigated under conditions of pulsed-gas chromatography within the temperature range of –80 to 500 °C. At temperatures up to about 180 °C adsorbed hydrogen was found to be displaced to the gaseous phase as a result of carbon oxide adsorption. At higher temperatures conversion of carbon monoxide and hydrogen to methane takes place.

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–80 500 °C. 180 °C . .

     

Effect of Rh/Al2O3 on the reduction of ZnO in a mechanical mixture of these components

The effect of reoxidation temperature on TPR of 5% Rh/Al₂O₃ catalyst and its mechanical mixture with ZnO has been investigated. The results suggest bimodal character of supported rhodium and surprisingly high effect of this metal on ZnO reduction in the mixture.

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5% Rh/Al₂O₃ ZnO. , ZnO .

     

High resolution surface imaging of Co/ZrO2 catalyst by TOF-SIMS

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a useful tool for the characterization of supported catalyst. Especially, the possibility of surface imaging appears very interesting. The images of not only elements distribution but also molecules or their fragments may be performed. Owing to the fast improvement of time-of-flight secondary ions mass spectrometers, obtaining the surface images with lateral resolution even below 100 nm is possible. The application of TOF-SIMS to the high resolution surface imaging of catalysts surfaces was shown. The influence of the preparation conditions of Co/ZrO₂ catalyst on the dispersion and composition of the active phase was investigated. The Co⁺/Zr⁺ and CoOH⁺/Zr⁺ intensity ratio values were calculated.     

Influence of calcination and lithium promotion on the surface properties of oxide supports

Thermal treatment and the addition of lithium influence the surface area of the oxides SiO₂, Al₂O₃ and MgO. A calcination temperature 1073 K causes a significant decrease of the surface area of SiO₂ and Al₂O₃; the same is not observed in case of MgO. Systems Li/MgO and Li/SiO₂ are characterized by a much smaller specific surface area than pure oxides thermally treated at the same temperature.     

Temperature-programmed hydrogen desorption from water on bimetallic catalysts Ir?Fe/Al2O3

Desorption of hydrogen liberated in the process of water decomposition on bimetallic catalysts (3% Ir–Fe/Al₂O₃) at linear temperature growth was observed. In the case of iridium the amounts of desorbing hydrogen are relatively small, whereas for iron they are many times greater.

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, 3% Ir–Fe/Al₂O₃ . , , .

     

Characterization of Ru/CeO2-Al2O3 catalysts and their Performance in CO2 Methanation

Ru/Al₂O₃ and Ru/CeO₂-Al₂O₃ samples were used as catalysts in CO₂ methanation. The catalysts were characterized by temperature-programmed reduction (TPR) and X-ray diffraction. The promoting effect of ceria on the cataytic activity of the catalysts under study in CO₂ methanation was observed.     

Phase composition of a selective V2O5?Fe2O3 catalyst of methanol oxidation to formaldehyde

Redispersion of Re/SiO₂ catalysts during air-aging at ambient temperature has been confirmed by TEM analysis. The splitting of large primary crystallites (>10 nm) under the influence of the strain energy of the oxide layer formed on the Re surface has been proposed to explain the observed phenomenon.

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Re/SiO₂ . , Re(>10 nm), , .