Environmentally Friendly Photocatalytic Oxidation of Aromatic
Alcohol to Aldehyde in Aqueous Suspension of Brookite TiO
2
Maurizio Addamo Æ Vincenzo Augugliaro Æ Marianna Bellardita Æ
Agatino Di Paola Æ Vittorio Loddo Æ Giovanni Palmisano Æ
Leonardo Palmisano Æ Sedat Yurdakal
Received: 6 June 2008 / Accepted: 16 July 2008 / Published online: 5 September 2008
Ó Springer Science+Business Media, LLC 2008
Abstract Photocatalytic oxidation of 4-methoxybenzyl
alcohol to aldehyde in water has been achieved by using
home-prepared uncalcined brookite TiO
2
. Three different
lamp irradiances have been applied in order to check the
influence of light power on selectivity. Well known com-
mercial samples (Degussa P25 and Merck) have been used
for comparison purposes. A maximum selectivity towards
aldehyde of ca. 56% (i.e. ca. 3 times higher than that
obtained with commercial TiO
2
) has been achieved.
Keywords Selective photocatalysis Á Alcohol oxidation Á
Brookite TiO
2
1 Introduction
Photocatalytic reactions carried out by means of TiO
2
have
been commonly applied to purification of waste waters and
polluted air [1], and recently are finding industrial appli-
cations in several fields, such as in concrete materials or in
surgery rooms, and yet in self-cleaning anti-fogging glass
and textile applications [2]. Exploitation of photocatalysis
in organic selective reactions has been achieved in organic
solvents or in gas phase [3]. Very few examples of such
reactions in aqueous environmentally friendly solvents
have been reported [4]. Very recently our group has
employed home prepared anatase and rutile TiO
2
samples
to perform the partial oxidation of aromatic alcohols to
aldehydes in water [5] by obtaining good conversions and
selectivities. The selective oxidation of alcoholic group is a
key step throughout many organic syntheses.
Here we report the 4-methoxybenzyl alcohol (MBA)
partial oxidation carried out in water without any organic co-
solvents in the presence of home-prepared pure brookite
TiO
2
. The formed aldehyde (p-anisaldehyde) is a species
used in sweet blossom and flavour compositions for con-
fectioneries and beverages and, furthermore, an intermediate
in many different industrial processes.
The study was performed with two initial alcohol
concentrations and three irradiation powers. The ortho-
rhombic polymorph brookite TiO
2
has received less
attention in the past, due to difficulties in synthesis to
yield a single phase product. In recent years, however,
new methods of brookite preparation have been developed
[6] though not all have achieved pure brookite phase.
Nanocrystalline TiO
2
sample, in which brookite is the
predominant phase, was produced [6g] by a sol process
under ambient condition and tested for methyl orange
degradation in water where it showed a photocatalytic
activity higher than that of Degussa P25 and rutile phase
titania samples. Home-prepared brookite samples have
been prepared here by following a calcination-free method
recently optimised by our group [6i], starting from TiCl
4
aqueous HCl solutions, that implies the peptization with
pure water of suspensions where pure particles of rutile
and brookite are contemporary present. After decantation
the surnatant of suspension, constituted of only brookite,
was separated and dried.
M. Addamo Á V. Augugliaro (&) Á M. Bellardita Á A. Di Paola Á
V. Loddo Á G. Palmisano Á L. Palmisano (&) Á S. Yurdakal
‘‘Schiavello-Grillone’’ Photocatalysis Group, Dipartimento di
Ingegneria Chimica dei Processi e dei Materiali, Universita
`
degli
Studi di Palermo, Viale delle Scienze, 90128 Palermo, Italy
e-mail: augugliaro@dicpm.unipa.it
L. Palmisano
e-mail: palmisano@dicpm.unipa.it
S. Yurdakal
Kimya Bo
¨
lu
¨
mu
¨
, Fen Faku
¨
ltesi, Anadolu U
¨
niversitesi,
Yunus Emre Kampu
¨
su
¨
, 26470 Eskisehir, Turkey
123
Catal Lett (2008) 126:58–62
DOI 10.1007/s10562-008-9596-0