C. Noupa et al., SIZABLE DEACTIVATION EFFECT FOR THE 1,3-BUTADIENE HYDROGENATION ON VAPOR-DEPOSITED PD AGGREGATES ON GRAPHITE, Catalysis letters, 22(3), 1993, pp. 197-203
The catalytic activity of Pd aggregates vapor-deposited on graphite ha
s been measured in the 1,3-butadiene hydrogenation. It is generally de
creasing with particle size. But, such a decrease is largely depending
upon the hydrogen and the hydrocarbon pressure. Indeed, with low hydr
ocarbon pressure (about 1 Torr) and in presence of large excess of hyd
rogen (pH(2)/PC4H6 = 100) the activity of the smaller aggregates is co
mparable to that of larger particles. The different behaviour is conse
quently attributed to a size dependent deactivation. Such a deactivati
on could be due to carbon deposits generated by dehydrogenation of the
diene admolecules. This behaviour is tentatively related with marked
differences observed by XPS on the smaller aggregates, both with respe
ct to the core level energies and to the density of states into the va
lence band.