Effect of H2S-uptake on the conversion of cyclohexene on Ru- and Pd-promoted molybdena-alumina catalysts

The effect of H₂S on the activity and selectivity of catalysts (Ru/Al₂O₃, Pd/Al₂O₃ and Ru and Pd promoted molydena-alumina) was different (on differnt catalysts and different conversions of cyclohexene). Ru-containing catalysts showed higher sulfur sensitivities than the Pd-containing ones. The sequence of catalysts by their H₂S uptake related to mass of catalyst was PdMo/Al₂O₃RuMo/Al₂O₃Mo/Al₂O₃>Pd/Al₂O₃Ru/Al₂O₃.     

Methane Reforming with Carbon Dioxide on Cobalt-Containing Catalysts

Cobalt- and iron-containing catalysts supported on MgO, ZrO₂, -, -, and -Al₂O₃ were synthesized and studied in the CO₂ reforming of methane. The CoO/-Al₂O₃ systems are the most active and stable. The dependence of the catalytic activity and the degree of reduction on the amount of supported CoO was studied. In the active catalysts, CoO is weakly bound to the support and can readily be reduced to metal cobalt. Coke formed in the course of the reaction does not affect the activity of the CoO/-Al₂O₃ catalyst.     

Composite Pd/Pr4O7/C catalysts: Synthesis, dispersity and properties

The catalysts prepared sequentiallyvia the interaction of C₃H₅PdC₅H₅ with the surface of evacuated Pr₄O₇/C and reduction with H₂ at 573 K, contain 20–30 Pd particles and Pr₄O₇ particles<20 . The catalysts obtained have two-order of magnitude higher specific activity in the CH₃OH synthesis than Pd/C.     

Oxidative ammonolysis of 3-picoline on mixed oxide catalysts

The oxidative ammonolysis of 3-picoline has been studied on the following catalysts: V₂O₅ on corundum, V₂O₅ with the addition of 1% of H₂WO₄ on corundum, V₂O₅ + MoO₃ + P₂O₅ (10.350.35) on silica gel, V₂O₅ + Al₂O₃, and a melt of V₂O₅ + TiO₂ (10.22). Mixed catalysts of vanadium and titanium oxides exhibited the highest activity and selectivity. With the passage of 25–45 moles of oxygen (in the form of air), 5–10 moles of ammonia, and 50–70 moles of water per mole of 3-picoline at a temperature of 390–410° C, the amount of nicotinonitrile formed on these catalysts amounted to 85–90% of the theoretically possible amount.Part LXIII of the series Oxidation of organic compounds; for part LXII, see [1].     

Hydrogenating Activity and Adsorption Capacity of Supported Nickel Catalysts Modified by Heteropoly Compounds

The catalytic activity, adsorption capacity, and pore structure of low-percentage nickel catalysts supported on -Al₂O₃or activated carbon and modified by tungsten heteropoly compounds are studied. The activity, selectivity, and thermal stability of the catalysts in the vapor-phase hydrogenation of olefins and aromatic hydrocarbons are higher than those for conventional nickel catalysts. The concentration of nickel in the catalysts is 10–15 times lower than that in commercial catalysts. However, the modified catalysts have higher specific surface areas of metal, higher dispersion, a uniform distribution of metal particles, and a pore-radius distribution other than in the support. The study of water adsorption and desorption showed that the heteropoly compound modifying the -Al₂O₃support covers the support surface completely, and supported nickel interacts with the active surface of the modifying agent rather than with Al₂O₃. A hydrogenation mechanism is proposed, which involves H₂dissociation on Ni particles and the subsequent diffusion of hydrogen atoms via a spillover mechanism to the adsorbed organic compound with the participation of the OH groups of the modifying agent.     

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.     

The Mechanism of Methane Reforming with Carbon Dioxide: Comparison of Supported Pt and Ni (Co) Catalysts

The interaction of the catalyst 5.16 wt % Pt/-Al₂O₃ with ₄, ₂, ₂, and ₄ + ₂ pulses is studied using a setup involving the differential scanning calorimeter DSC–111 and a system for chromatographic analysis. Comparison of the results obtained with analogous data on Ni/Al₂O₃ and Co/Al₂O₃ suggests that methane activation occurs via a common pathway via dissociative chemisorption on the metal surface with the formation of ₂ and carbon on all the catalysts studied. Carbon dioxide activation on Pt/Al₂O₃ differs from its activation on Ni()/Al₂O₃. It follows from the enthalpy of formation that carbon on Pt/Al₂O₃ is graphite-like in contrast to carbide carbon on Ni(Co)/Al₂O₃. This graphite carbon is more stable and less reactive.     

Physicochemical properties of Ti-grafted SBA-15

Partial oxidation of n-heptane to syngas at 400–450°C was investigated over Rh and Rh-Ni based catalysts. The Rh/-Al₂O₃ catalyst exhibited much better catalytic activity than the Rh-Ni/-Al₂O₃ catalyst. A combination of the Rh-based catalyst with the WGS reaction catalyst (Fe₃O₄—Cr₂O₃) increases the hydrogen selectivity but has no distinct effect on shifting the balance of the partial oxidation of n-heptane.This revised version was published online in December 2005 with corrections to the Cover Date.     

Effect of gamma-irradiation on surface and catalytic properties of Co3O4 doped with NiO

NiO-doped Co₃O₄ samples precalcined at 500 °C were subjected to various doses of -rays within the range 0.2-1.6 MGy. The particle size and BET-surface areas of different samples were determined using XRD and nitrogen adsorption at -196 °C. The catalytic reactions studied were conversion of ethanol and isopropanol at 250-400 °C using a micropulse technique and H₂O₂ decomposition in aqueous solution at 30-50 °C. The results revealed that the -irradiation brought a significant decrease in the particle size of Co₃O₄ phase with subsequent increase in the S_BET surface areas. The treatment brought also a progressive decrease in the total conversion of both alcohol (dehydration and dehydrogenation) falling to a minimum value (about 20% of its initial activity) at a dose of 0.8 MGy. The catalysts retain their initial activity upon exposure to a dose of 1.6 MGy. On the other hand, the catalytic activity in H₂O₂ decomposition of the investigated system decreased progressively by increasing the dose of -rays and the catalysts lost more than 90% of their initial activity upon exposure to a dose of 1.6 MGy.