Journal of Chemical Technology and Biotechnology J Chem Technol Biotechnol 79:1293–1300 (online: 2004) DOI: 10.1002/jctb.1128 Characteristics of photocatalytic oxidation of gaseous 2-propanol using thin-film TiO 2 photocatalyst Chiu-Ping Chang, 1,2∗ Jong-Nan Chen 1 and Ming-Chun Lu 3 1 Institute of Environmental Engineering, National Chiao Tung University, Hsinchu 300, Taiwan 2 Department of Environmental Engineering and Health, Yuanpei University of Science and Technology, 306, Yuanpei St, Hsinchu 300, Taiwan 3 Department of Environmental Resources Management, Chia Nan University of Pharmacy and Science, Tainan 717, Taiwan Abstract: This work presents a photocatalysis-based method to treat and purify air because of its broad applicability to common, oxidizable, air contaminants. The effect of oxygen content, temperature, water vapor, and 2-propanol concentration on the TiO 2 surface was investigated. The rate of 2-propanol decomposition increased with increasing the oxygen content, but was reduced at temperatures higher than 100 ◦ C. When water vapor concentration was in the range of 10–355 mmol m −3 , the rate of 2-propanol decomposition was proportional to the water content. However, an opposite result was observed at a higher concentration of water vapor. 2-Propanol was photooxidized to acetone, and eventually to carbon dioxide and water. The kinetic model of 2-propanol photooxidation was successfully developed by the competitive Langmuir–Hinshelwood rate form, incorporating the inhibition effect coming from the formation of acetone.  2004 Society of Chemical Industry Keywords: photocatalysis; titanium dioxide; kinetics; 2-propanol; acetone NOTATION C a Acetone concentration (mmol m −3 ) C a0 Initial concentration of acetone (mmol m −3 ) C CO 2 Carbon dioxide concentration (mmol m −3 ) C p 2-Propanol concentration (mmol m −3 ) C p0 Initial concentration of 2-propanol (mmol m −3 ) k a Reaction rate constant of acetone (mmol m −3 s −1 ) k p Reaction rate constant of 2-propanol (mmol m −3 s −1 ) K a Adsorption equilibrium constant of acetone (m 3 mmol −1 ) K p Adsorption equilibrium constant of 2-propanol (m 3 mmol −1 ) r a Reaction rate of acetone (mmol m −3 s −1 ) r a0 Initial reaction rate of acetone (mmol m −3 s −1 ) r CO 2 Reaction rate of CO 2 (mmol m −3 s −1 ) r p Reaction rate of 2-propanol (mmol m −3 s −1 ) r p0 Initial reaction rate of 2-propanol (mmol m −3 s −1 ) t Reaction time (s) α Fraction of directly oxidized from adsorbed 2- propanol to carbon dioxide. 1 INTRODUCTION The interest in heterogeneous photocatalysis to remove trace organic compounds present in air exhaust streams and in indoor environments is intense and increasing. Heterogeneous photocatalysis is a pro- cess in which the illumination of an oxide semicon- ductor, usually the anatase form of titanium diox- ide, creates photoexcited electrons (e − ) and holes (h + ). The attractive advantages of this technol- ogy are: (i) photocatalytic oxidation can proceed at ambient temperature and pressure; (ii) the excitation source can be sunlight or low-cost fluorescent light sources; (iii) photocatalysts are generally nontoxic, inexpensive, and chemically and physically stable; and (iv) final oxidation products are usually innocuous. The photocatalytic oxidation of single compounds, namely alkanes, 1 alkenes, 2 alcohols, 3–7 ketones, 8–10 aromatics 10 – 12 and halogenates 13 – 15 has been previ- ously reported. Volatile organic compounds (VOCs) can be vapor- ized at significant rates. Some are toxic and car- cinogenic, and are regulated individually as haz- ardous pollutants. 16 The serious problem related to the emission of VOCs is that they participate ∗ Correspondence to: Chiu-Ping Chang, Department of Environmental Engineering and Health, Yuanpei University of Science and Technology, 306, Yuanpei St, Hsinchu 300, Taiwan E-mail: Changcp@mail.yust.edu.tw Contract/grant sponsor: National Science Council, Taiwan, ROC; contract/grant number: NSC 91-2211-E009-031 (Received 30 September 2003; revised version received 25 April 2004; accepted 23 June 2004) Published online 7 September 2004  2004 Society of Chemical Industry. J Chem Technol Biotechnol 0268–2575/2004/$30.00 1293