Performance enhancement of elemental mercury removal from syngas over Fe7SC sorbent: Experimental and theoretical studies

Abstract

In this study, a Fe7SC sorbent was prepared via hydrothermal impregnation and used to eliminate Hg0 from simulated syngas. A certain amount of oxygen was introduced to induce targeted H2S oxidation to form active surface sulfur species for the enhanced capture of Hg0 over Fe7SC. The effects of the introduced oxygen, temperature, and syngas composition (H2S, CO, H2, and H2O) on Hg0 adsorption performance were investigated. X-ray photoelectron spectroscopy, Hg0-temperature programmed desorption, and density functional theory calculations were performed to elucidate the Hg0 removal mechanism. Fe7SC exhibited a superior Hg0 removal performance (approximately 99.2%) in the presence of H2S + O2 at 150 °C. The interaction between H2S and the introduced oxygen was responsible for its superior Hg0 capture capacity. CO and H2 suppressed Hg0 adsorption, and H2O inhibited Hg0 removal owing to competitive adsorption. Results of the Bangham kinetic analysis indicate that Hg0 surface chemisorption is the primary rate-controlling step. Hg0 adsorption on the Fe7SC sorbent may follow the Eley–Rideal mechanism, in which the active sulfur species generated from H2S oxidation react with gaseous Hg0 to form HgS.