Selective Hydrogenation of Benzonitrile by Alumina-Supported Ir–Pd Catalysts

The kinetics of liquid-phase hydrogenation of benzonitrile have been examined alumina supported Ir, Pd and Ir–Pd catalysts. Benzonitrile disappearance TOF is 10-fold higher for Pd catalyst than it is for Ir catalyst. Benzylamine is produced preferentially over Pd, whereas dibenzylamine is produced principally over Ir. Non-monotonic activity and selectivity relationships with bimetallic composition are obtained.     

Synthesis and Characterization of Catalytically Activity Fe3o4–3-Aminopropyl-triethoxysilane/Pd Nanocomposite

Herein we report the fabrication and characterization of Pd decorated Fe₃O₄ nanoparticles as highly effective catalysts for hydrogenation of 4-nitroaniline and 1,3-dinitrobenzene in liquid phase. The fabricated Fe₃O₄ nanoparticles exhibit an average size of 12 nm and super paramagnetic character with a high saturation magnetization (80 emu/g). The surface –NH₂ groups effectively binds the in situ formed Pd nanoparticles. Thus formed Fe₃O₄–APTES–Pd(0) catalyst showed a very high catalytic activity in reduction reactions of 4-nitroaniline and 1,3-dinitrobenzene in liquid phase. Electron donor –NH₂ groups supported Pd may be responsible for the increased catalytic activity. The superparamagnetic character of this system allows easy recovery and multiple uses without significant loss of its catalytic activity.     

Structure-activity Relation of Fe2O3–CeO2 Composite Catalysts in CO Oxidation

A series of Fe₂O₃–CeO₂ composite catalysts were synthesized by coprecipitation and characterized by X-ray diffraction (XRD), BET surface area measurement, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Their catalytic activities in CO oxidation were also tested. The Fe₂O₃–CeO₂ composites with an Fe molar percentage below 0.3 form solid solutions with the CeO₂ cubic fluorite structure, in which the doped Fe³⁺ initially substitutes Ce⁴⁺ in fluorite cubic CeO₂, but then mostly locate in the interstitial sites after a critical concentration of doped Fe³⁺. With an Fe molar percentage between 0.3 and 0.95, the Fe₂O₃–CeO₂ composites are mixed oxides of the cubic fluorite CeO₂ solid solution and the hematite Fe₂O₃. XPS results indicate that CeO₂ is enriched in the surface region of Fe₂O₃–CeO₂ composites. The Fe₂O₃–CeO₂ composites have much higher catalytic activities in CO oxidation than the individual pure CeO₂ and Fe₂O₃, and the Fe_0.1Ce_0.9 composite shows the best catalytic performance. The structure-activity relation of the Fe₂O₃–CeO₂ composites in CO oxidation is discussed in terms of the formation of solid solution and surface oxygen vacancies. Our results demonstrate a proportional relation between the catalytic activity of cubic CeO₂-like solid solutions and their density of oxygen vacancies, which directly proves the formation of oxygen vacancies as the key step in CO oxidation over oxide catalysts.     

Characterization and Evaluation of Methylcyclopentane and Cyclohexane Ring Opening over Ir/ZrO2–MoO3 Catalysts

Methyl bromide was synthesized by reacting methane with oxygen and hydrogen bromide over Rh/SiO₂ catalyst. The reaction started from the oxidation of HBr to form active bromine species (Br^? radicals and Br* surface species), which in turn reacted with CH₄ to form CH ₃ ^? radicals and $\hbox{CH}_{3}^{\ast}$ surface species. These CH ₃ ^? and $\hbox{CH}_{3}^{\ast}$ species reacted with the active bromine species to form CH₃Br and CH₂Br₂. The presence of HBr inhibited the deep oxidation and the steam reformation of CH₄ and therefore, guaranteed the high selectivity of CH₃Br. In the presence of HBr, CO was formed from the oxidation and steam reformation of CH₃Br, while CO₂ was formed from the oxidation and steam reformation of CO over Rh/SiO₂ at reaction temperature higher than 560 °C.     

Methane Oxidation Over Pd Supported on Ceria–Alumina Under Rich/Lean Cycling Conditions

Catalysts with highly dispersed palladium on alumina, alumina doped with 20 wt% ceria and ceria have been prepared, characterized and examined for net-lean methane oxidation. In particular, the activity and selectivity were investigated during rich/lean cycling of the feed. The ceria content is found to influence both the general and the instantaneous activity responses. The results indicate that the active phase of palladium changes between reduced and oxidised Pd during the rich/lean cycling, and that the process is influenced by the presence of ceria.     

Research of the Activity of Catalysts on the Base of H3PW12O40 in Partial Oxidative Conversion of C3–C4 alkanes

Catalysts from heteropoly acid H₃PW₁₂O₄₀ and its Cs, Na, Ba, Pb, Ca, Cd, Cr, Mn, V, La salts supported on clinoptilolite, alumosilicate are highly active in oxidative conversion of propane–butane (OCPB) mixture and formation of C₂–C₄ olefins, oxygen-containing compounds at temperatures T = 100–800 °C. Optimum yields of ethylene and propylene are achieved on heteropoly acid its Cs and Cr salts. The processes of oxidative dehydrogenation (ODPB) and cracking are concurrent in formation of olefins. High activity is caused by dispersity of supported catalysts (XRD, IRS) both formation of crystal hydrates and an amorphous phase of heteropoly acid in a condition of interaction with the carrier.     

Catalytic Performance of Aged Rh/CeO2–ZrO2 for NO–C3H6–O2 Reaction Under a Stoichiometric Condition

The activity of Rh/CeO₂ for NO reduction by C₃H₆ was gradually deceased by mixing with ZrO₂ until 68 mol%. Rh supported on CeO₂–ZrO₂ with higher OSC was found to show lower catalytic activity. High OSC of CeO₂–ZrO₂ would probably stabilize the surface of Rh in oxidized state, resulting in low activity and low efficiency of C₃H₆ utilization for NO reduction. In situ FT-IR spectroscopy suggested that mononitrosyl species such as Rh(NO)^δ? and Rh(NO)^δ+ are reaction intermediates in the NO–C₃H₆–O₂ reaction over Rh/CeO₂–ZrO₂ catalysts.     

Enhancement of Catalytic Activity on Pd/C and Te–Pd/C During the Oxidative Dehydrogenation of Sodium Lactate to Pyruvate in an Aqueous Phase Under Pressurized Oxygen

The oxidative dehydrogenation of sodium lactate to sodium pyruvate in an aqueous phase proceeded favorably using Pd/C and that doped with Te at 358 K with no adjustment in solution pH under pressurized oxygen, although previous reports had stated that this reaction would not proceed using Pd/C while Pd/C doped with either Pb, Bi or Te showed the activity at atmospheric pressure, 363 K, and a pH of 8.     

Characterization of Pd/γ-Al2O3 Catalysts Prepared Using [Pd(hfac)2] in Liquid CO2

A series of Pd/γ-Al₂O₃ catalysts was prepared from [Pd(hfac)₂] (hfac = hexafluoroacetylacetonate) in liquid carbon dioxide using the method reported by Kim et al. [Chem Mater 18:4710 (2006)]. The catalysts were characterized using CO pulse chemisorption, diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray absorption fine structure (XAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron microscopy. The catalysts were reduced initially in the high-pressure CO₂ reaction cell using H₂ at 75 °C. Samples were removed, stored in a desiccator, and re-reduced in situ at 250 °C prior to pulse chemisorption, DRIFTS and XAFS. CO pulse chemisorption evidenced that the Pd dispersion decreased from 55% to 5% as the Pd loading increased from 0.58 to 3.94 wt.%. The as-prepared 0.58 and 1.77 wt.% Pd/γ-Al₂O₃ catalysts (after air exposure) contained oxidized Pd species that were converted after in situ reduction to supported Pd particles. The average Pd particle sizes of these two catalysts (16 and 23 Å, respectively) estimated from the first-shell Pd–Pd coordination numbers are in good agreement with the CO chemisorption results. DRIFTS evidenced a prevalence of weakly bound linear CO (ν_CO = 2083 cm^?1) adsorbed on the 0.58 wt.% Pd catalyst. A 2.95 wt% Pd catalyst (49 Å average particle size) also exhibited a strong linear CO band (ν_CO = 2093 cm^?1). In contrast, CO chemisorption on a commercial 1 wt.% Pd/Al₂O₃ catalyst (37 Å average particle size) gave predominantly 2-fold bridging CO species. We infer that the supported Pd particles prepared from [Pd(hfac)₂] are rougher on the atomic scale (with a higher percentage of edge and corner atoms) than equivalently sized particles in conventionally prepared Pd/γ-Al₂O₃ catalysts.