REACTION BETWEEN H2S AND ZINC-OXIDE TITANIUM-OXIDE SORBENTS .1. SINGLE-PELLET KINETIC-STUDIES

The reduction, sulfidation, and regeneration characteristics of high-temperature desulfurization sorbents composed of zinc and titanium oxides in varying molar ratios have been studied in an electrobalance reactor. The addition of titanium oxide reduces the tendency for zinc oxide reduction and subsequent volatization of metallic zinc, thereby increasing the maximum sorbent operating temperature. The reaction parameters studied include temperature, pressure, pellet diameter, and reactive gas concentration. The high-pressure test results are particularly significant since previous single-pellet desulfurization sorbent testing has been limited to atmospheric pressure. At a constant mole fraction of reactive gas, the global rate of both the sulfidation and regeneration reactions increased with pressure. However, at constant reactive gas concentration, increasing the pressure reduced the global reaction rate. In the temperature range of primary interest (650-760 °C), the sulfidation reaction rate was independent of temperature, while the regeneration rate was a relatively weak temperature function. Little deterioration in sorbent reactivity was observed after five reduction and sulfidation cycles with four intervening regeneration cycles. © 1990, American Chemical Society. All rights reserved.