II International Symposium on Carbon for Catalysis ABSTRACTS

OP-I-4
As it can be seen, potassium permanganate gives place to the greatest increase in both the
concentrations.
All the supports of Tab. 1 have then been contacted with a palladium acetate solution
dissolved in benzene (2 g of supports with 50 ml of a benzene solution of palladium acetate)
for 2-3 hours. In the mentioned range of time all the palladium is adsorbed from the solution.
The prepared catalysts contained about 1% by weight of palladium with the exception of the
support prepared by oxidation with 1 M potassium permanganate that have been prepared
with 3% by weight of palladium. An increase of -COOH and -OH would favour palladium
dispersion as a consequence of the surface reaction:
---- COOH + Pd(OOCCH 3 ) 2 ---- COOPd(OOCCH 3 ) + CH 3 COOH
The dispersion of all the prepared catalysts has been determined by measuring hydrogen
chemisorption with a pulse method [4] and the obtained results are always summarized in
Tab. 1. As it can be seen, all the catalysts resulted well dispersed and the effect of the
oxidating treatment in some cases is significant even if not very strong. In particular there is
not a direct correlation between the increase of –COOH and –OH concentrations and
dispersion. This will be discussed and justified.
All the prepared catalysts have been submitted to an activity test consisting in the
measurement in a batch reactor of the reaction rate of the cyclo-octene hydrogenation. The
obtained results are always reported in Tab. 1. As it can be seen drastic treatments are
detrimental while the oxidation in mild condition gives place to an improvement of the
performances.
The properties and catalytic performances of the prepare Pd-carbon catalysts have also been
compared with catalysts containing roughly the same amount of palladium but prepared by
using other different supports, such as: alumina, silica and silica alumina and other palladium
precursors. A discussion on the method more suitable for obtaining very high dispersed
catalysts will conclude the work.
References
[1] H.P. Boem; Advances in Catalysis 16,19 (1966)
[2] A. King; J. Chem Soc. 20, 1489 (1937)
[3] S. Studebaker; Rubber Chem. Technology 30, 1401(1957)
[4] L. Maffucci, P. Iengo, M. Di Serio, E. Santacesaria
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