Vi. Parvulescu et al., HYDROGENATION OF VINYLBENZENES ON PD-TM AL2O3 AND TM/AL2O3 CATALYSTS/, Journal of the Chemical Society. Faraday transactions, 93(9), 1997, pp. 1827-1835
Citations number
53
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
Pd-Tm/gamma-Al2O3 catalysts containing 0.1% Pd-1% Tm, 0.3% Pd-1% Tm an
d 0.5% Pd-1.% Tm, respectively have been obtained by successive impreg
nation of gamma-Al2O3, first with palladium and then with thulium. Int
roduction of Tm leads to an increase in the conversion of vinylbenzene
s compared to that with monometallic Pd/gamma l-Al2O3 catalysts. For m
onocomponent Pd/gamma-Al2O3 catalysts, turnover frequency (TOF) is unc
hanged. For bicomponent Pd-Tm/gamma-Al2O3 catalysts, if one considers
that the reaction occurs only on the Pd particles, then introduction o
f Tm seems to increase the TOF. However, by taking Tm into considerati
on when calculating the TOF, then the bicomponent catalysts are seen t
o behave as the monocomponent catalysts. This behaviour is highlighted
also by using the Koros-Nowak criterion. If Tm is not considered to b
e an active species, vinylbenzene hydrogenation appears to be controll
ed by mass transfer processes. However, the texture characteristics of
the bicomponent catalysts are not sufficiently modified by Tm introdu
ction to support such a hypothesis. On the contrary, by considering th
e Tm participation in the reaction, the slope of the Koros-Nowak depen
dence is included in a range typical for kinetically controlled reacti
ons.