TiO2 nanoparticles were prepared with strict control of the size, molecular mass (PDI = 1.02), and mass density by hydrolyzing a precursor, Ti(acac)2(biphen), in the presence of a well-defined hollow Pd12L24 spherical endotemplate. The formation of highly monodisperse TiO2 nanoparticles was confirmed by (1)H NMR spectroscopy, MALDI-TOF mass spectrometry, transmission electron microscopy, and atomic force microscopy. The template was easily removed by treating the sphere with a metal scavenger followed by calcination to give crystalline TiO2 nanoparticles (2.0 ± 0.2 nm in diameter), which showed photocatalytic activity.
Ein sphärischer Pd12L24‐Komplex dient als Templat bei der Synthese von hohlen Siliciumdioxidnanopartikeln, die Metallcluster mit definierter Atomzahl n in ihrem Inneren enthalten. Der eingeschlossene Pd12L24‐Komplex wird in der schützenden Siliciumdioxidhülle zunächst in einen (PdO)n‐Oxidcluster umgewandelt und anschließend zum Pdn‐Metallcluster reduziert.
Ein sphärischer Pd12L24‐Komplex dient als Templat bei der Synthese von hohlen Siliciumdioxidnanopartikeln, die Metallcluster mit definierter Atomzahl n in ihrem Inneren enthalten. Der eingeschlossene Pd12L24‐Komplex wird in der schützenden Siliciumdioxidhülle zunächst in einen (PdO)n‐Oxidcluster umgewandelt und anschließend zum Pdn‐Metallcluster reduziert.
We studied the synthesis of 1,3-butadiene via the dehydration of crotyl alcohol (2-buten-1-ol) over solid acids. Crotyl alcohol conversion and butadiene selectivity were both 95 % or more over commercial silica _ alumina catalysts. However, a sudden decrease in catalytic activity was observed during the reaction. On the basis of the fact that the deactivated catalyst was regenerated by drying at 150-200 °C, it was revealed that the main cause of the catalyst deactivation was the adsorption of water formed during the reaction and not the coke formation. An analysis of the deactivated catalyst indicated that, since the formation of Al _ OH by the hydrolysis of the Al _ O _ Al bond increased the hydrophilicity of the catalyst surface, the adsorption of water on the catalyst surface was promoted, whereas that of crotyl alcohol was probably inhibited. Moreover, on the basis of the catalyst characterization, it was concluded that silica _ alumina catalysts with few silanol groups, few alumina-rich zones, and a low Si/Al ratio were preferable.
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