Photon Factory Activity Report 2005 #23 Part B (2006)
Materials Science

7C/2004G295

Preparation of (Cr,Ti)-containing Mesoporous Silica Photocatalyst
Using a Photo-assisted Deposition MethodYosuke MASUI1, Satoshi OHSHIRO1, Yasutaka KUWAHARA1, Masakazu ANPO2,1
1
1
1
Tetsutaro OHMICHI , Iwao KATAYAMA , Kosuke MORI , and Hiromi YAMASHITA*
1
Division of Materials and Manufacturing Science, Graduate School of Engineering,Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
2Department of Applied Chemistry, Graduate School of Engineering,Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
Introduction
It is vital to develop the photocatalysts which canoperate efficiently under visible light irradiation with highselectivity. In this study, the (Cr, Ti)-binary oxide
containing mesoporous silica photocatalyst was preparedby the application of a photo-assisted deposition (PAD)
method which can realize the direct interaction between
Cr-oxide and Ti-oxide moieties. The photocatalytic
reactivity of (Cr, Ti)-containing mesoporous silica undervisible light irradiation for the epoxidation of propene
with oxygen has been investigated [1, 2].
Experimental
Ti or Cr - containing hexagonal mesoporous silica (TiHMS, Cr-HMS) were synthesized by the sol-gel method.
(Cr, Ti)-binary oxide containing mesoporous silica,
PAD.Cr/Ti-HMS was prepared by using a photo-assisted
deposition (PAD) method; Cr-oxide was deposited on Ti –HMS from aqueous solution of Cr(NO)3 under UV lightirradiation (λ > 220 nm) for 24 hours. The sample wastreated in centrifuge and dried before calcined at 823 K.
The photocatalytic oxidation of propene with oxygen
under visible light (λ > 450 nm) and UV light (λ > 220nm) irradiation was carried out at 273 K for 2 hours.
Results and Discussion
Fig. 1 shows the XANES spectra of referencecompounds, Ti-HMS, Cr-HMS and PAD.Cr/Ti-HMS at Ti
K-edge and Cr K-edge. Compared with the referencecompounds, it is confirmed that the tetrahedrally
coordinated Ti-oxide and Cr-oxide moieties have been
formed on PAD.Cr/Ti-HMS. In Fig. 1, the intensity of
preedge peak of PAD.Cr/Ti-HMS at Ti K-edge decreased
after the application of the PAD method. It indicates thedirect interaction between Ti-oxide and Cr-oxide moieties.
Scheme 1. shows the formation of (Cr, Ti)-binary oxide
moieties with direct interaction.
In photocatalytic oxidation of propene with oxygen
under light irradiation, PAD.Cr/Ti-HMS exhibited activity
under visible light (λ > 450 nm) irradiation and thereaction proceeded with high selectivity for partialoxidation. (Table 1).

Fig. 1. XANES spectra of reference compounds,Ti-HMS, Cr-HMS and PAD.Cr/Ti-HMS at Ti K-edge
and Cr K-edge.
OTiOhνCrO Cal.

O4+O (λ > 200 nm)

TiOOOCr ionOOOO
Ti3+OOOScheme 1. Design of (Cr,Ti)-binary oxide byphoto-assisted deposition (PAD) method.
Table 1. Products distribution of propene oxidation withoxygen on various catalysts under light irradiation.
Catalysts

λConv. / %Ti-HMSUV

Ti-HMS

Selectivity / %POAC AL AA COx

503036101024

Visible0-----

PAD.Cr/Ti-HMS Visible

4063

71965

PO; propylene oxide, AC; acetone, AL; acrolein, AA; acetaldehyde, COx; CO + CO2References[1] H. Yamashita et al, Current Opinion in Solid State &Maters. Sci., 7, 471 (2004)[2] H. Yamashita et al, Chem. Commun., 435 (2001).
* yamashita@mat.eng.osaka-u.ac.jp

Users' Report121