Oxidation Of Acetone In Air Research Articles

Enhanced photocatalytic activity of mesoporous and ordinary TiO2 thin films by sulfuric acid treatment

Transparent anatase mesoporous TiO2 (MTiO2) and TiO2 nanometer thin films were prepared on soda-lime glass and fused quartz via the reverse micellar method and sol–gel method, respectively. The as-prepared MTiO2 and TiO2 films were then treated by dipping them in a H2SO4 solution. The MTiO2 and TiO2 films before and after surface acid treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), BET surface area and UV–VIS spectrophotometry. The photocatalytic activity of the samples was evaluated by photocatalytic oxidation of acetone in air. It was found that MTiO2 thin films showed higher photocatalytic activity than that of the TiO2 thin films. This was attributed to the fact that MTiO2 thin films were composed of smaller monodisperse spherical particles about 15nm and had higher specific surface areas. Furthermore, the monodispersity of TiO2 particles was beneficial to transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO2 particle and reduced the recombination of photo-generated electrons and holes. The films deposited on quartz showed the highest photocatalytic activity because films deposited on quartz exhibited a better crystallization and had no sodium contaminant. The photocatalytic activity of MTiO2 and TiO2 thin films deposited on different substrates after treated with H2SO4 solution was significantly enhanced. Acid treatment was particularly effective for MTiO2/glass and TiO2/glass, which showed activity enhancement of four and over two times, respectively. This increase in activity has been correlated with the reduction of sodium ions and the increase in the adsorbed hydroxyl content on the surface of TiO2 films.

Investigation on TiO2-coated optical fibers for gas-phase photocatalytic oxidation of acetone

A preliminary optical fiber reactor (OFR) that employs bare quartz fibers as a light-transmitting support of TiO2 was tested for gas treatment by investigating photocatalytic oxidation of acetone in air (50–750ppmv). Using one or four TiO2-coated fibers in a continuous flow photoreactor, a steady-state conversion up to 80% was achieved at ambient temperature and pressure. The kinetic behavior of the acetone conversion in this study could be described by zero-order kinetics. The characteristics of coated-optical fibers were quantitatively analyzed and their use in photocatalytic gas treatment was discussed in detail. All the acetone molecules degraded was quantitatively converted to CO2 with no intermediates detected. No noticeable deactivation was observed within a few hours’ operation under the present experimental conditions. The conversion of acetone linearly increased with the incident light intensity without showing any sign of saturation. The transmitted light intensity through a TiO2-coated optical fiber exponentially decreased along the fiber, showing 90% extinction within 30cm. The photocatalytic conversion measured as a function of the coated-fiber length showed a similar trend. An optimal coating thickness was found at around 1.5μm above which the photocatalytic efficiency was reduced. The presence of water vapor reduced the reactivity due to the competitive adsorption on active surface site with acetone. While a measurable conversion of acetone was observed in the absence of O2, increasing O2 concentration up to 15% effectively enhanced the conversion.

Influence of Thermal Treatment on the Adsorption of Oxygen and Photocatalytic Activity of TiO2

Thermal treatment in air has a marked influence on the adsorption of oxygen and the photocatalytic activities of TiO2 (P25) for the oxidation of acetone in air. The photoactivity of TiO2 increases ...

An investigation on photocatalytic activities of mixed TiO2-rare earth oxides for the oxidation of acetone in air

The photocatalytic activities of the mixtures of TiO2 (P25) with three rare earth oxides were investigated. The effects of the rare earth oxide contents and calcination temperature on the photocatalytic activities were studied. The results reveal that the mixtures of TiO2 with La2O3 (0.5 wt.%) or Y2O3 (0.5 wt.%) calcined at 700 °C or 650 °C exhibit higher photoactivity than pure TiO2 (P25) for the oxidation of acetone. On the other hand, the mixtures of TiO2 with CeO2 have lower photoactivity than pure TiO2. Experimental results of polycrystalline X-ray diffraction, photoexcited transient absorption decay and zeta potential measurements show that the presence of these rare earth oxides can inhibit anatase to rutile transformation at elevated temperatures. The lower photocatalytic activity of TiO2/CeO2 mixtures can be explained by the fast recombination rate of photogenerated electron-hole pairs and high isoelectric point in terms of pH value. The preparation method of these mixtures is also described.

Mechanisms of the Cl-atom-initiated oxidation of acetone and hydroxyacetone in air

The products of the Cl-atom-initiated oxidation of acetone and hydroxyacetone (CH3COCH2OH) in O2–N2 mixtures at 700 Torr and 298 K have been identified using long-path-length FTIR spectroscopy and long-path-length UV–visible diode array spectroscopy. The oxidation of acetone yields methyl glyoxal (CH3COCHO), HCHO, CO, CO2, CH3COOH, CH3OH, HCOOH and O3 as identifiable products. The data have been analysed, utilising the results of a kinetic study of the oxidation of acetone in air. The mechanism of the oxidation proceeds initially via the production of acetonylperoxy radicals (CH3COCH2O2) which are removed by their self-reaction (3), and reaction with other peroxy radicals [CH3C(O)O2, CH3O2 and HO2] produced by the subsequent chemistry: 2CH3COCH2O2→ 2CH3COCH2O + O2(3a), → CH3COCHO + CH3COCH2OH + O2(3b), The thermal decomposition of CH3COCH2O radicals produced in channel (3a) into CH3CO radicals and HCHO, is shown to predominate over the alternative reaction with O2, under the conditions of these experiments: CH3COCH2O + M → CH3CO + HCHO + M (12), CH3COCH2O + O2→ CH3COCHO + HO2(13), Measurements of the yields of HCHO and CH3COCHO are consistent with the operation of both channels of reaction (3) and allow certain conclusions to be drawn concerning the reactions of CH3COCH2O2 with CH3O2 and CH3C(O)O2.