The diiron‐substituted silicotungstate γ‐SiW10{Fe3+(OH2)}2O386− (schematically shown) is an effective catalyst for the oxygenation of alkenes in homogeneous reaction media with 1 atm of molecular oxygen. For example, a selectivity for cyclooctene oxide of 98 % and a turnover number of 10 000 were achieved in the epoxidation of cyclooctene. The catalyst is stable under the reaction conditions, and its ability to use molecular oxygen raises the prospect of using it in industrial epoxidation processes.
The gas-phase hydrogenation of acetonitrile was studied with
silica-supported platinum catalysts of which
the degrees of metal dispersion were widely changed by reduction
conditions. The activities were found to
decrease gradually during the course of reaction for all the catalysts
examined. The initial rate of reaction
increased with an increase in the degree of platinum dispersion,
D. Triethylamine was the only main product
irrespective of D and period of reaction time. The
initial turnover frequency, TOF0, was shown to be
smaller
for larger D values. This dependence of
TOF0 on D was explained by the electronic state
of the surface of
the platinum particles and the state of acetonitrile molecules adsorbed
on them on the basis of X-ray
photoelectron spectroscopy and Fourier transform infrared spectroscopy
measurements. The surface layer of
smaller particles is more favorable for the adsorption of acetonitrile.
The acetonitrile is adsorbed by platinum
with the electron lone pair of nitrogen in the antibonding orbital, but
electron back-donation does not takes
place. As a result, the C⋮N bonds of acetonitrile adsorbed on
smaller particles are stronger and more difficult
to hydrogenate.
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