Function of sulfur dioxide in the kinetic mechanism of oxidation of carbon

Retardation of the gasification reaction of carbon with oxygen by SO2 was observed. Rates of oxidation were determined by thermal gravimetric analysis (TGA) of a nuclear graphite in the temperature range of 550 to 7000C, and of a coconut charcoal in the temperature range of 400 to 5050C. The oxidant gases were dry air containing 0 to 6% SO2. Reduction of the rate by SO2 varied with burn-off. Differential thermal analysis (DTA) was also applied to detect the retardation effect of SO2. The technique of infrared internal reflection spectroscopy (IRS) was used to examine the surface species of reacted charcoal samples. Absorption bands were assigned to surface carbonyls, lactones, and a chemisorbed SO2 in the form of sulfate. Retardation of the oxidation reaction was attributed to chemisorption of SO2. (author)