Effect of synthesis conditions on photocatalytic activity of TiO2 powders synthesized in supercritical CO2

被引:35
作者
Alonso, E. [1 ]
Montequi, I. [1 ]
Cocero, M. J. [1 ]
机构
[1] Univ Valladolid, Dep Chem Engn & Environm Technol, High Pressure Proc Grp, E-47011 Valladolid, Spain
关键词
Titanium dioxide; Photocatalytic activity; Supercritical synthesis; Nanoparticles; Anatase; Photocatalyst; DEGRADATION; DISPERSION; SCALE;
D O I
10.1016/j.supflu.2009.01.005
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
TiO2 anatase nanoparticles have been synthesized by thermal-hydrolysis of diisopropoxititanium bis (acetylacetonate) (DIPBAT) in supercritical carbon dioxide (SC-CO2). Operational variables, such as hydrolysis reactant, pressure, temperature and residence time, have a strong influence on TiO2 properties, and therefore in the final application of the titanium dioxide. Photocatalytic activity of the obtained TiO2 has been tested in the oxidation of methylorange (MeO) in aqueous solutions. The obtained results show that synthesis pressure (in the range 10-20 MPa) does not affect the photocatalytic activity of formed TiO2 anatase. Isopropyl alcohol appears as a better hydrolysis reactant than ethanol, since the formed TiO2 presents higher photocatalytic activity. When synthesis temperature is increased from 200 degrees C to 300 degrees C, crystallite size of the particles is enhanced, revealing the improvement of crystalline quality and indeed of photocatalytic activity. The proposed synthesis process can be operated in a continuous way, and from the present results, a residence time of 1 min is enough to obtain TiO2 nanoparticles with a photocatalytic activity similar to commercial powders. TiO2 particles have been subjected to a post-calcination process at 550 degrees C, 700 degrees C and 900 degrees C, and the experimental results show that the anatase phase is very stable and there is not a transition phase to rutile up to 900 degrees C. Moreover, a post-calcination treatment is not suitable from the catalysis point of view since the photocatalysis point of view since the photocatalytic activity decreases, and the proposed synthesis process without any heat post-treatment is appropriated. (C) 2009 Elsevier B.V. All rights reserved.
引用
收藏
页码:233 / 238
页数:6
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