Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 7, Issue 6, Pages 3797-3806Publisher
AMER CHEMICAL SOC
DOI: 10.1021/am508769x
Keywords
photocatalysis; catalyris; titanium dioxide; Degussa (Evonik) P25; imines
Funding
- Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) [26289296]
- Grants-in-Aid for Scientific Research [26289296] Funding Source: KAKEN
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Photoirradiation (lambda > 300 nm) of Degussa (Evonik) P25 TiO2, a mixture of anatase and rutile particles, in alcohols containing nitroaromatics at room temperature produces the corresponding imines with very high yields (8096%). Other commercially available anatase or rutile TiO2 particles, however, exhibit very low yields (<30%). The imine formation involves two step reactions on the TiO2 surface: (i) photocatalytic oxidation of alcohols (aldehyde formation) and reduction of nitrobenzene (aniline formation) and (ii) condensation of the formed aldehyde and aniline on the Lewis acid sites (imine formation). The respective anatase and rutile particles were isolated from P25 TiO2 by the H2O2/NH3 and HF treatments to clarify the activity of these two step reactions. Photocatalysis experiments revealed that the active sites for photocatalytic reactions on P25 TiO2 are the rutile particles, promoting efficient reduction of nitrobenzene on the surface defects. In contrast, catalysis experiments showed that the anatase particles isolated from P25 TiO2 exhibit very high activity for condensation of aldehyde and aniline, because the number of Lewis acid sites on the particles (73 mu mol g(1)) is much higher than that of other commercially available anatase or rutile particles (<15 mu mol g(1)). The P25 TiO2 particles therefore successfully promote tandem photocatalytic and catalytic reactions on the respective rutile and anatase particles, thus producing imines with very high yields.
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