Oxidation of hydrogen sulfide over microporous carbons

Abstract

Microporous carbon of high purity was produced by the carbonization of Saran at 900° followed by activation in either CO 2 at 900°, O 2 at 300°, or air at 425°. The activated carbons were characterized using N 2 adsorption at −195° CO 2 adsorption at 25°, and mercury and helium displacements. Hydrogen sulfide oxidation (at H 2S pressures between 0.4–3.8 Torr) by O 2 (in excess of stoichiometric amount) was studied between 100–160° using a microbalance, that is by weighing the build-up of sulfur on the carbon. The predominant reaction, H 2S + 1 2 O 2 → 1 2 S 2 + H 2O was first order in H 2S concentration and independent of O 2 concentration. The rate was only slightly reduced by sulfur build-up to at least 36%, by weight, on the carbon. The oxidation rate was significantly higher over the O 2-activated carbon than over the CO 2-activated carbon. Throughout the studies, oxidation rates could be correlated with area active to O 2 chemisorption. It is concluded that H 2S oxidation proceeds via rapid dissociative chemisorption of oxygen on carbon sites followed by reaction with H 2S. Rates of H 2S oxidation were also studies over commercial, granular activated carbons of significant ash contents.