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Solid Acid Catalysts from Clays: Preparation of Mesoporous Catalysts by Chemical Activation of Metakaolin under Acid Conditions
No full textNatural kaolin was treated at 850 or 950 °C in air flow to give respectively the metakaolin samples MK8 and MK9. The obtained materials were successively treated at 90 °C with a 1 M solution of H2SO4, for various time lengths. The acid treatment of MK8 was found to give a high surface area microporous material with good catalytic properties related to the high density of acid sites, while MK9 gave an ordered mesoporous material with a low density of acid sites. The materials were characterized by several techniques, X-ray powder diffraction, thermogravimetric analysis, N2 physisorption, scanning electron microscopy, and temperature-programmed desorption of ammonia. The 1-butene isomerization was used as test reaction to evaluate the acidity of the samples
One-pot mesoporous Al–Ce–Cu oxide systems as catalysts for the preferential carbon monoxide oxidation (CO-PROX)
No full textA series of organized mesoporous Al–Ce–Cu oxide systems, synthesized by a single-step method using
aluminum sec-butoxide as Al precursor and Cu and Ce stearates and/or nitrates as metal sources, have
been comparatively studied to evaluate the influence of some of the preparation parameters on their catalytic
behavior in the preferential oxidation of CO (CO-PROX) to CO2 in H2-rich gas streams. The catalytic
activity was tested in the 40–190 °C temperature range
Effect of the synthetic parameters on the textural and catalytic properties of ordered mesoporous Cu-Ce-Al systems
No full textEnvironmentally friendly Friedel-Crafts acylation of 2-methoxynaphtalene catalyzed by beta zeolite
No full text
Photocatalytic performance of Cu-doped titania thin films under UV light irradiation
No full textWe investigated the effect of copper doping on the photocatalytic properties of TiO2 thin films. Titania thin films
doped with three different copper concentrations were synthesized via radiofrequency-assisted (RF) magnetron
sputtering, then annealed at 600 ◦C in controlled atmosphere (Ar, O2, H2 flow). The impact of the annealing in
inert, oxidizing or reducing atmosphere on the crystalline and surface structure, and photocatalytic performance
in the methylene blue degradation under UV light irradiation was investigated by X-ray diffraction, UV–Vis
Spectroscopy, Rutherford Backscattering Spectrometry, Scanning Electron Microscopy. Annealing induced very
different crystallization in different atmospheres, with strong copper out-diffusion in samples annealed in
reducing atmosphere and formation of large embedded nanoparticles. The Cu-doped titania films exhibited
higher photocatalytic activity than pure titania film and the best performing catalyst, treated in H2 atmosphere,
suggests that the presence of embedded copper nanoparticles (both metallic and oxidized) is able to strongly
enhance the photocatalytic properties of the host titania matrix. Incorporated Cu particles can act as trapped sites
for generated electrons, and this leads to the reduction of carrier recombination which, ultimately, plays a
significant role in the increase of photoactivity. The recyclability of the best system was ascertained by a suitable
3-cycle stability test
Nanocomposite materials based on submicrometer spheres of mesostructured MCM-41 silica and polystirene prepared through "living" radical polymerization
No full textLow-temperature carbon monoxide oxidation over zirconia-supported CuO–CeO2 catalysts: Effect of zirconia support properties
No full textA study was conducted to investigate the effect of the preparation route of ZrO2 in CuO–CeO2/ZrO2 catalysts for the oxidation of carbon monoxide at low temperature (COX). Four ZrO2 supports were synthetized via either type sol-gel methodology or precipitation. The final Cu-Ce-Zr oxide catalysts were prepared by incipient wetness co-impregnation with copper and cerium solutions (with a loading of 6 wt% of CuO and 20 wt% of CeO2). The catalyst crystalline phases, texture and active species reducibility were determined by XRD, N2 physisorption at −196 °C and H2-TPR, respectively; meanwhile the surface composition and copper-cerium electronic states were studied by XPS. The catalytic activity was evaluated in the oxidation of CO to CO2, in the 40–215 °C temperature range. Catalytic results evidenced that the samples prepared by a sol-gel methodology showed, after the impregnation, a severe decrease of specific surface area and pore volume attributable to a wide degree of pore blockage caused by the presence of metal oxide particles and a collapse of the structure partially burying the active sites. A simple co-impregnation of a zirconia support, obtained through facile and fast precipitation, provided instead a catalyst with very good redox properties and high dispersion of the active phases, which completely oxidizes CO in the range 115–215 °C with T50 of 65 °C. This higher observed activity was ascribed to the formation of a larger fraction of highly dispersed and easily reducible Cu species and ceria nanocrystallites, mainly present as Ce(IV), with an average size of 5 nm
Synthesis, characterization and catalytic activity of aluminum pillared synthetic Ti-, Fe- or Zn-substituted smectites
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