Search results for "Heterogeneous catalysis"

Oxidative degradation properties of Co-based catalysts in the presence of ozone

2007

Four series of cobalt-based catalysts, such as bare Co3O4 and CoO, CoOx-CeO2 mixed oxides, CoOx supported over alumina and alumina-baria and CoMgAl and CoNiAl hydrotalcites have been synthesized and investigated for the oxidative degradation of phenol in the presence of ozone. Characterizations were obtained by several techniques in order to investigate the nature of cobalt species and their morphological properties, depending on the system. Analyses by XRD, BET, TPR, UV-visible diffuse reflectance spectroscopy and TG/DT were performed. The CoNiAl hydrotalcite exhibits, after 4 h of reaction, the highest phenol ozonation activity followed by Co(3 wt%)/Al2O3-BaO and CoMgAl. The samples Co(1 …

A quantitative method of photoadsorption determination for irradiated catalyst in liquid–solid system

2009

WOS: 000266963000002

Photoassisted Mechanisms in Heterogeneous Catalysis: The Role of Surface OH in the Decomposition of Ethanoic Acid on Magnesium Oxide

1989

The photodecomposition of adsorbed ethanoic acid was studied on a number of pure and mixed insulator and semiconductor systems having a wide range of acid-base features. MgO appeared to be much more active than any other oxide when oxygen was not present in the reactant mixture. On the basis of infrared, U.V.-Vis. reflectance and photoluminescence data it is suggested that in this case the surface hydroxy-groups which are known to absorb at wavelengths longer than 300 nm are involved in the photodecomposition process.

Polyvinylpolypyrrolidone‐Stabilized Copper Nanoparticles as an Efficient and Recyclable Heterogeneous Catalyst for the Click of 1,2,3‐Triazoles in Wa…

2019

Selective propane oxidation over MoVSbO catalysts. On the preparation, characterization and catalytic behavior of M1 phase

2009

Nb-free (SbO)(2)M(20)O(56) catalysts (M = Mo, V) presenting pure M1 phase have been prepared by a post-synthesis treatment with hydrogen peroxide of a heat-treated MoVSbO mixed metal oxide catalyst previously prepared by hydrothermal method. The characterization of catalysts and their results for propane oxidation suggest that the optimization in the preparation of the M1 phase depends strongly on the washing procedure. The optimal removing of Sb species formed during post-synthesis treatment can explain the improvement in the catalytic activity; while the better selectivity to acrylic acid of the catalysts obtained by post-synthesis treatment can be explained by the elimination of M2 phase…

Oxidation of CH4 over Pd supported on TiO2-doped SiO2: Effect of Ti(IV) loading and influence of SO2

2009

Titania-modified silicas with different weight% of TiO2 were prepared by sol-gel method and used as supports for Pd (1 wt%) catalysts. The obtained materials were tested in the oxidation of methane under lean conditions in absence and in presence of SO2. Test reactions were consecutively performed in order to evaluate the thermal stability and poisoning reversibility. Increasing amounts of TiO2 improved the catalytic activity, with an optimum of the performance for 10 wt% TiO2 loading. Moreover, the titaniacontaining catalysts exhibited a superior tolerance towards SO2 by either adding it to the reactants or feeding it as a pure pretreatment atmosphere at 350 8C. Catalysts were characterize…

Activity of SiO2 supported gold-palladium catalysts in CO oxidation

2003

Abstract Bimetallic Au-Pd catalysts supported on silica with different Au/Pd atomic ratios were prepared by simultaneous reduction of palladium and gold precursors by ethanol in the presence of the polymer, polyvinylpyrrolidone (PVP). Formation of alloyed particles was detected by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and CO chemisorption measurements. The catalysts were tested in the catalytic oxidation of CO using a plug–flow reactor. The CO conversion was determined as a function of temperature. The monometallic palladium and the palladium-rich catalysts behaved quite similarly and were the most active catalysts. …

Preparation, Characterization and Photocatalytic Activity of TiO2 Impregnated with the Heteropolyacid H3PW12O40: Photo-assisted Degradation of 2-prop…

2009

Abstract Both commercial and home prepared TiO2 samples impregnated with tungstophosphoric acid (H3PW12O40) were prepared and used for the photo-assisted degradation of 2-propanol in gas–solid regime. The characterization results evidenced a good coverage of the polyoxometalate (POM) onto the surface of both types of TiO2 samples along with a marginal effect of the presence of ethanol or HCl during the POM impregnation step on the specific surface area, porosity, morphology, crystallinity and acidity of the samples. Propene was the main intermediate product found in 2-propanol photocatalytic degradation by using the samples containing POM as the photocatalyst, whereas propanone was mainly o…

Combined CO/CH4 oxidation tests over Pd/Co3O4 monolitic catalyst: effects of high reaction temperature and SO2 exposure on the deactivation process

2007

Abstract CO and CH 4 combined oxidation tests were performed over a Pd (70 g/ft 3 )/Co 3 O 4 monolithic catalyst in conditions of GHSV = 100,000 h −1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO 2 (5 ppm) on CO and CH 4 oxidation activity under lean condition ( λ  = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co 3 O 4 catalytic sites via chemisorbed SO 3 and/or sulphates occurred upon exposure to SO 2 . A treatment of regeneration to remove sulphate species was attempted by performing a heating/coolin…

CoMo catalysts supported on aluminosilicates: synergy between support and sodium effects

2004

Abstract The structural properties and the hydrodesulfurization (HDS) activity of sodium doped and sodium free CoMo catalysts supported on amorphous aluminosilicates (ASA) were investigated as a function of different SiO2:Al2O3 ratios. The support yielding the most active catalyst, (66% alumina) doped with different amounts of sodium, was used for a series of similar catalysts in order to study the effect of the alkali ion on the catalytic performance. The supports were prepared by sol–gel method and the catalysts were prepared by incipient wet impregnation method. The structure and the surface of the various samples were investigated by X-ray diffraction (XRD), temperature-programmed reduc…