Amorphous silica was modified by doping with titania through a surface sol–gel process and applied as the support for depositing
gold. These doped silica-supported gold catalysts were tested in the selective cyclohexane oxidation to cyclohexanone and
cyclohexanol using oxygen. Under the oxidation conditions of 150 °C, 1.5 MPa and 3 h, a selectivity of 91.7% for cyclohexanone
and cyclohexanol could be reached over the gold catalyst, affording a cyclohexane conversion of 8.4% and a turnover frequency
up to 40,133 per hour. Moreover, the catalytic activity and selectivity could be well retained in 4 recycling oxidation reactions,
showing a high stability of the gold catalyst supported on titania-doped silica. 相似文献
A novel PtPd/C nanowire catalyst with interconnected network and fewer great grain boundaries has been successfully prepared by templateless and modified phase‐transfer method using cetyltrimethylammonium bromide as a capping in ethylene glycol solution by microwave‐assisted process. Its structure, composition, and morphology are characterized by X‐ray diffraction, energy dispersive analysis of X‐ray, and transmission electron microscopy, respectively. The electrochemical measurements demonstrate that the highly dispersed and uniform PtPd/C nanowire networks catalyst has a significantly higher electrocatalytic activity and durability for the methanol oxidation as compared to solid solution PtPd/C. The greatly improved durability of PtPd/C nanowire networks catalyst is mainly a consequence of the unique interconnected network structure with fewer grain boundaries, which provide more facile pathway for the electron transfer, and inhibit the particle growth and agglomeration, as well as prevent the particles embedded in the microporous of carbon support to enhance the Pt utilization. 相似文献
Methane‐air partial oxidation to methanol over a ceramic‐supported Fe2O3‐CuO catalyst was investigated in a post‐plasma catalytic reactor at ambient conditions. The multicomponent catalyst exerted a better catalytic performance than the monocomponent Fe2O3 catalyst. Characterization of the catalysts by XPS showed that incorporation of the CuO additive to a Fe2O3‐based catalyst resulted in an increase of lattice oxygen in the surface of the catalyst which facilitated selective methane oxidation. Hydrogen temperature‐programmed reduction revealed that addition of the CuO promoter could improve the reduction performance of the catalyst. Moreover, this catalyst showed excellent stability and resistance against carbon deposition in the extended reactions while maintaining catalytic activity. A post‐plasma catalytic mechanism is proposed with three main pathways to methanol synthesis. 相似文献
Here, we report a facile synthesis of porous zinc-titanium oxide based mixed oxide nanoparticles having Zn/Ti molar ratio 1:2 based on evaporation-induced sol–gel route using Pluronic triblock copolymer P123 as a template. Use of volatile ethanolic media during the evaporation-induced self-assembly (EISA) method facilitates the formation of Zn–Ti mixed oxide heterostructure. Powder XRD data reveals that the composite material displayed ZnTiO3/TiO2 phases. Morphology, composition, porosity, nanostructure and thermal stability have been systematically investigated using small angle powder XRD, FE SEM-EDS, TEM, N2 sorption, FT IR and TG-DTA techniques. The observed BET surface area of Zn–Ti mixed oxide was 231 m2 g?1 with a typical mesopore diameter (~?5 nm) mostly arising from interparticle void space. The Zn–Ti mixed oxide catalyst showed bifunctional activity for Friedel–Craft benzylation of aromatics using benzyl chloride as well as partial oxidation of olefins under mild reaction conditions using dilute aqueous H2O2 as oxidant.
Graphical Abstract
Zn–Ti based porous nanoparticles synthesized using Pluronic P123 copolymer surfactant via EISA method has shown a very high surface area of 231 m2 g?1 and a significant bifunctional role for liquid phase oxidation and benzylation reaction.
Two vanadium phosphate catalysts (VPH1 and VPH2) prepared via hydrothermal method are described and discussed. Both catalysts
exhibited only highly crystalline pyrophosphate phase. SEM showed that the morphologies of these catalysts are in plate-like
shape and not in the normal rosette-type clusters. Temperature-programmed reduction in H2 resulted two reduction peaks at high temperature in the range of 600–1100 K. The second reduction peak appeared at 1074 K
occurred as a sharp peak indicated that the oxygen species originated from V4+ phase are having difficulty to be removed and their nature are less reactive compared to other methods of preparation. Modified
VPH2 gave better catalytic performance for n-butane oxidation to maleic anhydride contributed by a higher BET surface area, high mobility and reactivity of the lattice
oxygen associated to the V4+ which involved in the hydrocarbon’s activation. A slight increased of the V5+ phase also enhanced the activity of the VPH2 catalyst. 相似文献
The reaction mechanisms for diesel soot oxidation over V4/ZrO2 or V4/TiO2 oxide catalysts were studied by the means of in-situ UV-Raman spectroscopy. The results indicate that the formation of surface
oxygen complexes (SOC) is a key step and the SOC species mainly exist as carboxyl groups. The presence of NO in the reaction
gas stream can promote the formation of SOC species. For soot oxidation over V4/TiO2 catalyst, NO2 can be produced and remarkably accelerate soot oxidation. Based on the UV-Raman experimental results, two different reaction
mechanisms are proposed for soot oxidation over V4/ZrO2 or V4/TiO2 samples, respectively. 相似文献
A study of the effect of the aging atmosphere on the activity of co-precipitated copper zinc oxide catalysts for the ambient temperature oxidation of carbon monoxide is described and discussed. Four aging atmospheres are reported: air, N2, H2 and CO2, and both the precipitation and the aging of the precipitate were carried out by flowing these gases through the precipitation cell at constant pH and temperature. For all atmospheres, the surface area of the final CuO-ZnO catalyst increases with aging time and, consequently, the specific activity (mol CO converted/g catalyst/h) also increases. However, the intrinsic activity (mol CO converted/m2/h) initially decreases with aging time before attaining a steady level. The highest activity catalysts were obtained using air as the aging atmosphere and TPR studies indicate that this catalyst is less readily reduced. Catalysts prepared using CO2 as the aging atmosphere have lower activity, although the surface areas of these catalysts are not markedly lower. The study demonstrates that selection of the appropriate aging atmosphere, as well as the aging time, is an important parameter for the preparation of co-precipitated catalysts. 相似文献
Nanocrystalline magnesium oxide‐stabilized palladium(0) [NAP‐Mg‐Pd(0)], as an efficient catalytic system has been employed for the selective oxidation of alcohols using atmospheric oxygen as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using a set of optimal conditions. NanoActive™ Magnesium Oxide Plus, [NAP‐MgO] with its three‐dimensional structure and well‐defined shape acts as an excellent support for well dispersed palladium(0) nanoparticles. This catalyst can be recovered and reused for several cycles without any significant loss of catalytic activity. 相似文献
The perovskite-type oxide catalyst LaMnO3 prepared by the sol–gel method was found to be an efficient heterogeneous and recyclable catalyst for the wet aerobic oxidation of lignin to aromatic aldehydes. The lignin conversion rate and the yield of each aromatic aldehyde were enhanced significantly by the catalytic process as compared with the non-catalyzed process. Moreover, the activity, specific surface area and perovskite-type structure of the LaMnO3 catalyst remained nearly unchanged after five successive recycles of catalytic reactions. 相似文献
Supported gold catalysts on the mesoporous (MSP) metal oxides were prepared by a one-step, ultrasound-assisted reduction method,
and characterized by XRD, HRTEM, EDX, BET, and XPS analysis. Their catalytic activities were examined in the oxidation of
CO. Compared to the Au/Fe2O3(MSP) catalyst, the Au/TiO2(MSP) and Au/Fe2O3-TiO2(MSP) catalysts exhibited higher catalytic activity in the oxidation of CO at low temperatures. The high catalytic activity
of Au/TiO2(MSP) was attributed to the metallic state of the gold nanoparticles, their small size (2–2.5 nm), and their high dispersion
on the catalyst support. 相似文献