1,720,976 research outputs found
Photocatalytic degradation of VOCs in gas phase: study and comparison of surface features and reactivity of nano- and micro-sized TiO2
No full textThe photodegradation of toluene as model of VOC was experimentally studied using nano-sized TiO2 and micro-sized TiO2. A deep investigation using different analytic techniques was carried out onto the catalyst after several hours of use
Micro-sized TiO2 photocatalyst for the purification of air from acetone and acetaldehyde
No full textIn the last years increasingly restrictive regulations about the concentration limit of pollutants in air enhanced the development of more efficient treatment processes. In particular, advanced oxidation processes (AOPs) are chemical oxidation technologies that rely on the formation of the hydroxyl radical (OH ̇) to further oxide organic contaminants which are completely mineralized or converted to less harmful products. AOPs based on UV radiation involve photocatalysts, such as titanium dioxide (TiO2) mostly in nanometric size. However, nanoparticles give rise to many problems such as the catalyst-recovering, hindering their commercial application, other than possible damages on both human safety and environment .
The present paper reports a comparative study on the application of nano (P25 by Evonik) and micro-sized (1077 by Kronos) TiO2 samples as photocatalyst on degradation of acetone (AC) and acetaldehyde (AD).
Photocatalytic degradations of both pollutants were performed in a Pyrex glass cylindrical reactor of 5 L with 0.05 g of photocatalyst. The gaseous mixture in the reactor was obtained by mixing hot chromatographic air, humidified at 4, 40 and 75%, and an initial concentration of pollutant of 400 ppmV verified by an online micro-GC. The irradiation is carried out by an iron halogenide lamp (Jelosil, model HG 500) emitting in the 315-400 nm wavelength range (UV-A) with power of 30 W/m2.
As shown in Fig. 1 the activity of the micro-TiO2 is comparable with that of the nano-sized one even if it is a little bit slower. In both cases, micro-GC analyses detected the formation of CO2 after the degradation: experimental results indicate the formation of CO2 at 100%, confirming a full degradation of the starting molecule (acetone).
Considering these outcomes, the employment of micro-sized TiO2 as a photocatalyst turns out to be a valid alternative to the nano-sized catalysts. Moreover, in order to complete this study, TiO2 samples have been also doped with F to verify the influence of such a dopant on the material photoefficiency
Photocatalytic degradation of acetone, acetaldehyde and toluene in gas-phase : comparison between nano and micro-sized TiO2
No full textVolatile Organic Compounds (VOCs) are widely used in industrial processes and for domestic activities, so generating both water and air pollution. Well-known indoor sources of VOCs include cigarette smoke, building materials, paints, lacquers and cleaning products. The photodegradation of organic compounds by titanium dioxide TiO2 has been proposed as an alternative Advanced Oxidation Process (AOP) for the decontamination of air. In general AOPs based on UV radiation involve TiO2 mostly in nanometric size. However, nanoparticles give rise to many problems such as the catalyst-recovering, hindering their commercial application, other than possible damages on both human safety and environment.
In this contribution, a comparative study about the application of nano- (P25 by Evonik) and micro-sized (1077 by Kronos) TiO2 samples as photocatalyst in the degradation of acetone (AC), acetaldehyde (AD) and toluene (TL) is reported, in order to evaluate the feasibility of using micro-sized TiO2 instead of nanometric particles, which results in a greater environmental impact if compared to the former one.
Photocatalytic degradations of these pollutants were performed in a Pyrex glass cylindrical reactor of 5 L with 0.05 g of photocatalyst. The gaseous mixture in the reactor was obtained by mixing hot chromatographic air and an initial concentration of pollutant of 400 ppmV verified by an online micro-GC. The irradiation is carried out by an iron halogenide lamp (Jelosil, model HG 500) emitting in the 315-400 nm wavelength range (UV-A) with an irradiation power of 30 W/m2 [1]. As shown in Fig. 1 the activity of the micro-TiO2 is comparable with that of the nano-sized one. In particular, the amount of degraded AC is reported: the trend of degradation of the pollutant obtained with nanometric and micrometric TiO2 samples is quite similar.
Powdery samples were also characterized by FTIR-ATR analysis, performed with FTS-40 BIO RAD to evaluate the by-products adsorbed onto the photocatalyst surface.
As a consequence, this result demonstrates that micro-sized TiO2 powders are good candidates for the photocatalytic degradation of organic molecules in the gas phase
Effect of the surface fluorination on both nano- and micro-sized TiO2 for the toluene photodegradation in gas phase
No full textThe possibility to increase the photocatalytic performance of the micro-sized sample was investigated through the simple surface fluorination of a commercial sample (1077 by Kronos). Comparisons with the same surface treatment performed on P25 (Evonik) are reported on both surface characterizetion of the samples and photocatalytic activity towards the degradation of toluene in the gas phase
A redox cycle approach for the production of H2 by two-step methanol reforming
No full textIn the present work we studied the catalytic production of pure hydrogen from methanol and water using the spinel-type oxide CoFe2O4 (cobalt ferrite) as electron carrier. CoFe2O4 is an interesting material with an inverse spinel structure, and can be readily prepared by co-precipitation of the two oxides in basic media. The final material was obtained by calcinations, and two different calcination temperatures (Tcalc= 450 and 750°C) have been selected, to yield the corresponding CF450 and CF750 samples. A thorough physico-chemical characterization of the materials as a function of Tcalc was carried out. In fact, Tcalc induces some morphological changes in the material, strongly affecting, by aggregation, particles size and so leading to different catalytic performances. Another important aspect, related to Tcalc, seems to be the surface coke deposition, and this phenomenon should be minimized in order to maximize the hydrogen yield.
This work is aimed at establishing the influence of both crystal size and carbon deposition on the catalytic performance, in order to improve the stability of the material though several RedOx cycles
Gas-phase phenol methylation opver Mg/Me/O (Me=Al, Cr, Fe) catalysts: mechanistic implications due to different acid-base and dehydrogenating properties
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