The Reaction between Hydrogen Sulfide and Spherical Pellets of Zinc Oxide

The reaction between hydrogen sulfide and spherical pellets of zinc oxide was studied in a microbalance reactor at 375/sup 0/-800/sup 0/C. The gaseous mixture contained 1-6% H/sub 2/S diluted with hydrogen (added to stabilize H/sub 2/S) and nitrogen, with a 5:1 H/sub 2//H/sub 2/S molar ratio. Rapid and almost complete reaction occurred at 600/sup 0/-700/sup 0/C. Near 800/sup 0/C, slow decomposition of ZnO led to a vapor-phase reaction and deposition of nonporous ZnS on the pellet surface, which prevented further reaction. At below 600/sup 0/C, the reaction stopped well before total ZnO conversion was obtained. Experimental time-conversion results for the 600/sup 0/-700/sup 0/C range, where pore diffusion was the controlling resistance, were in good accord with values predicted by the Szekely et al. grain model. The strong deviation from the model predictions at lower temperatures were attributed to the dominant role of grain diffusion resistance. The H/sub 2/S-ZnO reaction is currently used in the desulfurization of hydrocarbon gases for synthesis of ammonia and has been suggested for sulfur removal in SNG processing.