Graphite oxidation in molten sodium carbonate

Abstract

The oxidation of spectroscopic grade graphite using air or oxygen in molten sodium carbonate was investigated at 900, 1000 and 1050†C. The oxidation rate increased with increasing temperature, increasing oxygen concentration, and increasing graphite surface area but decreased slightly as the reaction air was diluted with increasing carbon dioxide concentrations. At high-graphite loadings, the reaction rate was 0.45 order in oxygen, 0.45 order in graphite surface area with an apparent activation energy ( E a ) of 35 kcal/mole and appeared to tend toward a rate limit imposed by the available oxidant in the melt. At low-graphite loadings, the rate was 0.42 order in oxygen, 0.78 order in graphite surface area with E = 32 kcal/ mole and appeared to tend toward a rate limit imposed by the available graphite surface area. Virtually no carbon monoxide was observed under the conditions of the experiments. A sequence of reactions is proposed in which sodium peroxide, formed by the reaction of oxygen with sodium carbonate is the active oxidizing species.