Res. Chem. Intermed.
, Vol. 34, Nos 5–7, pp. 617–628 (2008)
Koninklijke Brill NV, Leiden, 2008.
Also available online - www.brill.nl/rci
In situ diffuse reﬂectance FT-IR studies of TiO
in photo-oxidation of benzene and ethylene
and YASUTAKE TERAOKA
Department of Energy and Material Sciences, Faculty of Engineering Sciences, Kyushu University,
Kasuga, Fukuoka 816-8580, Japan
Received 6 January 2007; accepted 9 January 2007
Abstract—In situ diffuse reﬂectance FT-IR measurements were carried out to investigate the
formation and decomposition behavior of by-product compounds on TiO
surfaces during the photo-oxidation of benzene and ethylene. In the benzene photo-oxidation
([benzene] = 100 ppm) without water vapor, TiO
catalyst was readily covered with oxygen-
containing by-product compounds, which were decomposed by photoirradiation in the presence of
water vapor ([H
O] = 0.17%) with an induction period. Pt deposition slightly increased the rate for
their decomposition. In the ethylene photo-oxidation ([ethylene] = 400 ppm) without water vapor,
oxygen-containing by-product compounds were also formed, which were readily decomposed by
photoirradiation in the presence of water vapor without induction period. Pt deposition on TiO
surface had no signiﬁcant effect on the photo-oxidation processes.
Keywords: Photo-oxidation; regeneration; TiO
; benzene; ethylene.
Photocatalytic oxidation (PCO) with TiO
is one of the useful techniques for the
treatment of air polluted with volatile organic compounds (VOCs) , especially
at their low concentration levels. For the last decade, many papers have been
published on the photo-oxidation of various types of VOCs, including aromatic
compounds [2–4], aliphatic compounds [4–6], alcohols  and halocarbons [6, 7].
These organic compounds are oxidized on TiO
surfaces to form CO
containing by-product compounds. However, the build-up of these by-product
compounds on the TiO
catalyst surface resulted in the deactivation of TiO
by covering the catalytic active sites in some cases of VOCs [4, 8], depending
on the structure of organic substrates and reaction conditions. The reactivites
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