Kinetics of the photocatalytic oxidation of gaseous acetone over platinized titanium dioxide
The photocatalytic oxidation of acetone is investigated in a flow-circulating reactor over Pt/TiO{sub 2} prepared by photodeposition (Pt/TiO{sub 2}-P) as well as by reduction with NaBH{sub 4}(Pt/TiO{sub 2}-C). Compared to untreated TiO{sub 2}, Pt/TiO{sub 2}-P is less active and Pt/TiO{sub 2}-C more active at 40--120 C, water concentration of 4500 ppm, and light intensity of 1.10 x 10{sup {minus}6} E/(min cm{sup 2}). The increased activity of Pt/TiO{sub 2}-C is related to the stronger adsorption of acetone and higher rate constant, as revealed by dependence of the reaction rate on concentration. Adsorption constants obtained from adsorption isotherms are significantly lower than those constants obtained from the dependence of the rate on acetone concentration. This suggests the presence of acetone photoadsorption during photocatalytic oxidation. Platinized samples did not demonstrate steady state deactivation, which was observed over TiO{sub 2} at temperatures above 100 C. However, there was a decrease in the oxidation rate while reaching steady state after an increase of temperature to 80 C and above. Apparent activation energy of photocatalytic oxidation over platinized samples was 10--13 kJ/mol; the apparent activation energy of thermal acetone oxidation was 84 kJ/mol for Pt/TiO{sub 2}-P and about 40 kJ/mol for Pt/TiO{sub 2}-C. At 80--140 C, photoinduced oxidation could occur on Pt particles, as shown by acetone photoinduced oxidation over Pt/{gamma}-Al{sub 2}O{sub 3}. The lack of deactivation of Pt/TiO{sub 2} above 100 C may be related to the modification of the TiO{sub 2} surface during Pt deposition because TiO{sub 2} treated with NaBH{sub 4} demonstrated a higher deactivation temperature. The dependence of activity on Pt content in Pt/TiO{sub 2}-C had a peak at Pt content of about 0.1 wt%. The TiO{sub 2} used in this study had higher adsorption and rate constants compared to TiO{sub 2} Degussa P25. An estimate showed that there were no concentration gradients inside the photocatalyst film under experimental conditions of this study.
- Research Organization:
- Boreskov Inst. of Catalysis, Novosibirsk (RU)
- OSTI ID:
- 20014535
- Journal Information:
- Journal of Catalysis, Vol. 189, Issue 2; Other Information: PBD: 25 Jan 2000; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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