Activation of Pt/TiO 2 Catalysts by Structural Transformation of Pt-Sites
- PDF / 210,008 Bytes
- 4 Pages / 595.276 x 793.701 pts Page_size
- 48 Downloads / 156 Views
Catalysis Letters Vol. 107, Nos. 1–2, February 2006 (Ó 2006) DOI: 10.1007/s10562-005-9723-0
Activation of Pt/TiO2 catalysts by structural transformation of Pt-sites Xiaoyan Shia, Changbin Zhanga, Hong Hea, Masashi Shoub, Ken-ichi Tanakab,*, Shinichi Sugiharac, and Yoshitaka Andoc a
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China b Saitama institute of Technology, 1690 Fusaiji, Okabe, Saitama, Japan c Eco-Device Co., Saitama Industrial Technology Center, 3-12-18 Kamiaoki, Kawaguchi, Saitama, Japan
Received 12 January 2004; accepted 17 November 2005
Superior activation of on 1 wt% Pt/TiO2 catalysts for the oxidation of CO was attained by loading a large amount of Fe-oxide (100 wt%) and TiO2. In situ IR spectra of CO proved that the structural transformation is brought about on the Pt-sites by loading of Fe-oxide, where predominant Pt-sites giving linear CO change to highly reactive bridge CO Pt-sites. In contrast, no transformation of the linear CO sites to the bridge CO sites takes place by loading of TiO2 but the environment of Pt-sites for linear CO is changed. KEY WORDS: Pt/TiO2 catalyst; structural transformation of Pt-sites.
The role of support oxides and promoters changing the activity and/or the selectivity of precious metals is an interesting but unsolved puzzle in heterogeneous catalysis, although it has been empirically explained by dispersion in suitable size particles, formation of active perimeter, and changing the local density of states of metallic particles. Incredible catalytic activity of Au particles is a good example. Haruta et al. [1] showed that Au particle changes superior active catalyst for the oxidation of CO when the particles become smaller than 3 nm. Such active Au particles can be prepared on suitable oxides via [Au(OH)nC14-n]-ion in alkaline solution [2], it is difficult to rationalize the mechanism why the activity is so crucial on the size. Recently, Fu et al. [3] claimed that nano-size metallic Au particles might not contribute to the water-gas shift reaction on an Au/CeO2–La catalyst, where the non metallic Au ion may be the active site for the water–gas shift reaction, and it is similar on the Pt/CeO2–La catalyst. In this paper, we proposed a new activation method of Pt-catalyst based on Pt-site restructuring. As shown in previous paper [4], incredible activation of 1 wt% Pt/Al2O3 catalyst is attained by loading a large amount of FeOx (100 wt% in Fe) on it, on which selective oxidation of CO in excess H2 is brought about in ca. 90% selectivity. We supposed that the activation mechanism by loading FeOx might be different from ordinary synergetic effect such as observed on a 5% Pt/ AI2O3 catalyst by adding Fe-oxide [5–7]. In this paper, we show the spectroscopic evidence for the reconstruction of Pt-sites induced by Fe-oxide (mainly Fe2O3). on * To whom correspondence should be addressed. E-mail: [email protected]
1 wt% Pt/TiO2 catalyst, which may be responsible for the superior activation of Pt-catalyst. A 1 wt% Pt/TiO2 prepared
Data Loading...
