II International Symposium on Carbon for Catalysis ABSTRACTS

Results and discussion
OP-I-6
The Table summarizes the effect of the activation treatment of the carbon on the catalytic
properties of Pt catalysts prepared by both methods
Both catalysts prepared by impregnation with the same dispersion behave similarly in
dioxane, with comparable initial reaction rate, total conversion within 6-7 h and a very good
selectivity to Bzal. In dioxane/alkaline aqueous solution, conversion of Bzol to Bzal was very
rapid, but while Bzal was totally converted to the acid in the presence of 2%Pt imp /C35C, only
46% of Bzoic were produced over 3%Pt imp /C44A. These results are attributed to the polar
groups on C44A which make the catalyst hydrophilic and retains a water film on the metallic
surface.
The catalysts prepared by cationic exchange were surprisingly very poorly dispersed
(5 and 20%). Dispersion of Pt in 3%Pt ex /C35C ox and consequently the catalytic activity in
dioxane/alkaline aqueous solution could be improved, by heating C39C ox under Ar at 500°C
(noted C ox cal) to selectively eliminate carboxylic groups and preserve phenolic groups. Further
improvement could be obtained by decomposition of the catalyst precursor under air, before
the reduction step (noted C ox cal and C ox/Ar cal ). However the performances were lower than
those of 2%Pt imp /C35C.
Table: Oxidation of Bzol (100 mmol l -1 , 100 ml solvent, 1 g catalyst, 100°C, 10 bar air).
Dispersion In dioxane In dioxane/alkaline water
(%) Initial rate Bzol conv Bzal yield Bzol conv Bzoic yield
mol h -1 -1
mol Pt (%)/h (%)/h (%)/h (%)/h
2%Pt imp /C44A 44 51 100/6 95/6 100/2 46/23
2%Pt imp /C35C 35 63 99/7 98/7 99/2 98/23
2.7%Pt ex /C39A 20 7 94/23 86/23 100/4 39/23
3%Pt ex /C39C ox 5 7 91/23 85/23 100/4 20/23
3%Pt ex /C39C ox/Ar 15 100/3 66/23
3%Pt ex /C39C ox calc 19 100/3 95/23
3%Pt ex /C39C ox/Ar cac 24 100/2 95/23
In conclusion, the activation treatment of this synthetic carbon and the mose of deposition
of Pt are of prime importance for activity of the resulting supported platinum catalyst in
selective oxidation of benzylalcohol.
References
[1] R.A. Sheldon, I. W. C. E. Arends, A. Dijksman, Catal. Today 2000, 57, 157.
[2] P. Korovchenko, C. Donze, P. Gallezot, M. Besson, Appl. Catal. B, revised manuscript.
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