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Hydrogenation reactions are the most common examples where transition
and noble metal nanoparticles are applied in colloidal solution as quasihomogeneous
catalysts [1]. The main drawback in the use of colloidal
nanoparticles for catalysis concerns the recovery and reuse of these particles.
This is especially important if environmental issues are considered. Therefore,
attention has been drawn to the use of supported nanoparticles.
In this work, Ce-Ti-O supports were synthesized by the solvothermal method
using methanol and a cationic surfactant (CTAB). Pt
nanoparticles were then supported by photochemical
deposition using a low-pressure mercury lamp with
an emission line at 254 nm (ca.3 W of radiant flux)
during 4 h. The catalysts were calcined in N2 (4 h,
100 mL min-1), reduced in H2 (2 h, 20 mL min-1) and
flushed again with N2 during 30 min at 773 K.
Ultrafine platelet shaped CeO2 particles with
sizes ~ 3-8 nm were also produced by the
solvothermal method. When Ti was combined with
Ce, a nanostructured network was obtained. It was
proved that Pt spherical nanoparticles (diameter ~ 2-4 nm) can be efficiently
photodeposited on these supports. Fig.1 shows a HRTEM micrograph of the
Pt/Ce-Ti-O catalyst, where a Pt nanoparticle (marked by an arrow) can be
identified. These catalysts were tested in the selective hydrogenation of
cinnamaldehyde to cinnamyl alcohol. Enhancement in the catalytic activity for
cinnamaldehyde hydrogenation and higher selectivity for cinnamyl alcohol
production was observed with the Pt nanoparticles supported on Ce-Ti-O when
compared with the single-oxide supports (CeO2 and TiO2).
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Citação
Silva, Adrián; Machado, Bruno; Gomes, Helder; Gomes, Helder; Figueiredo, José; Drazic, Goran; Faria, Joaquim (2008). Photodeposition of Pt nanoparticles on Ce-Ti-O. In XXI Encontro Nacional da Sociedade Portuguesa de Química. Porto.