Search results for "O2"

Synthesis of high-surface area CeO2 through silica xerogel template: influence of cerium salt precursor”;

2010

Abstract Ceria nanosized oxides with high surface area were synthesized by means of a templating approach, using a porous silica xerogel with surface area as high as 718 m2/g. After impregnation of the silica template with the cerium salt solution and further calcination at 600 °C, the final ceria oxide was recovered by dissolving the silica framework in NaOH solution. The effect of cerium counteranion, nitrate or chloride, on the textural and reduction properties of the ceria oxide was examined. Characterizations by BET and pore size distribution, XRD, TPR and SEM/EDX techniques were performed. The silica xerogel templated approach resulted in the preparation of ceria with surface area of …

The morphology of block copolymer micelles in supercritical carbon dioxide by small-angle neutron and x-ray scattering

1997

Above its critical point, carbon dioxide forms a super-critical fluid, which promises to be an environmentally responsible replacement for the organic solvents traditionally used in polymerizations. Many lipophilic polymers such as polystyrene (PS) are insoluble in CO2, though polymerizations may be accomplished via the use of PS-fluoropolymer stabilizers, which act as emulsifying agents. Small-angle neutron and X-ray scattering have been used to show that these molecules form micelles with a CO2-phobic PS core and a CO2-philic fluoropolymer corona. When the PS block was fixed in length and the fluorinated corona block was varied, the number of block copolymer molecules per micelle (six to …

Reactive Polymers: A Versatile Toolbox for the Immobilization of Functional Molecules on TiO2 Nanoparticles

2006

Photoelectrocatalytic selective oxidation of 4-methoxybenzyl alcohol in water by TiO2 supported on titanium anodes

2013

The photoelectrocatalytic partial oxidation of 4-methoxybenzyl alcohol in aqueous solution irradiated by near-UV light was carried out in a three-electrode batch reactor. TiO2 films were either deposited by dip-coating of a TiO2 sol onto a Ti foil and subsequent calcination or generated on Ti plates by thermal oxidation in air at 400-700 degrees C. The effects of the anode preparation method and bias potential values on conversion and selectivity to the corresponding aldehyde were investigated. The photoelectrocatalytic results were compared with the photocatalytic and electrocatalytic ones. The results indicated that no reaction occurred during the electrocatalytic experiments, whereas the…

Overview on oxidation mechanisms of organic compounds by TiO2 in heterogeneous photocatalysis

2012

This review provides the reader with a general overview on heterogeneous photocatalytic oxidation mechanisms in the presence of TiO2, with a special address to conversion of aliphatic and aromatic organic species. The aim was to clarify the steps of the photo-oxidation of the various classes of compounds and to relate them with the properties of the catalysts and the experimental conditions used. Reactions carried out to perform complete degradation and photocatalytic partial oxidations have been deeply discussed. Recent isotopic studies highlighted new reaction pathways concerning partial oxidation of alcohols to aldehyde and oxidation of benzene while EPR investigations confirmed that not…

Unexpectedly ambivalent O-2 role in the autocatalytic photooxidation of 2-methoxybenzyl alcohol in water

2015

An unusual autocatalytic photooxidation of 2-methoxybenzyl alcohol has been observed under UV irradiation in aqueous medium. The homogeneous oxidation is catalyzed by the corresponding aldehyde that is also the main oxidation product. The trend of alcohol disappearance rate matches the typical shape of an autocatalytic process, where a crucial and ambivalent role is played by the presence of molecular oxygen. Low oxygen concentrations give rise to a zero-order reaction since the beginning of irradiation, while higher amounts of oxygen reduce the alcohol oxidation rate until the aldehyde reaches a concentration high enough to speed up the alcohol's conversion. Experiments performed by varyin…

Aqueous selective photocatalytic oxidation of salicyl alcohol by TiO2 catalysts: Influence of some physico-chemical features

2021

Abstract Partial photocatalytic oxidation of salicyl alcohol (2-hydroxybenzyl alcohol) to salicylaldehyde in water was investigated under environmental friendly conditions in the presence of home-prepared and commercial TiO2 (Merck and Aeroxide P25) samples under UVA irradiation. The photocatalysts were characterized by using BET, XRD, SEM and/or TEM techniques. The effects of crystallinity degree, pH (3–11) and presence of a hole trap (ethanol) on the photocatalytic activity and product selectivity were investigated. 4-Hydroxybenzyl alcohol was also used to study the influence of the position of the substituent group in the aromatic ring. High alcohols conversion and product selectivity va…

Nanostructured rutile TiO2 for selective photocatalytic oxidation of aromatic alcohols to aldehydes in water

2008

WOS: 000253100100022

Kinetics of 4-Methoxybenzyl Alcohol Oxidation in Aqueous Solution in a Fixed Bed Photocatalytic Reactor

2010

WOS: 000280384800004

Photocatalytic oxidation of trans-ferulic acid to vanillin on TiO2 and WO3-loaded TiO2 catalysts

2015

Abstract The photocatalytic oxidation of trans-ferulic acid to vanillin in water has been studied by using various TiO2 and WO3-loaded TiO2 samples as catalysts. Different values of selectivity were obtained depending on the physico-chemical properties of the single samples and a vanillin selectivity of 10% was reached in the presence of the commercial TiO2 Merck. Higher selectivity values were obtained by impregnation of TiO2 with H2WO4 followed by calcination. The increased production of vanillin exhibited by the obtained WO3-loaded TiO2 powders was attributed to a reduced further oxidation of the aldehyde caused by the presence of the practically inactive tungsten trioxide hydrate on the…