CATALYTIC EFFECT OF VANADIUM, IRON AND LEAD-OXIDES ON THE OXIDATION OF MODERATOR GRAPHITE

The catalytic effect of the oxides V2O5, Fe2O3 and PbO on the air oxidation of graphite has been investigated. Graphite surfaces were contaminated with the oxides by soaking in standard solutions of the metal ions. The oxidation reaction was monitored kinetically, by differential thermal oxidation, and chemically, using X-ray photoelectron spectroscopy. The results showed that PbO and V2O5 were active catalysts, increasing the rate by up to 16 times at 450 degrees C, in the case of V2O5. By contrast, the catalytic activity of Fe2O3 was low. A mechanism is proposed to explain the catalytic activity of PbO and V2O5 based on the interaction of metal orbitals with the pi-system of graphite.