The mechanism of coal gas desulfurization by iron oxide sorbents

• The existence of CO and H2 affects equilibrium concentrations of H2S and COS.
• The presence of H2 has a negative effect on H2S removal.
• By-products including COS, CS2, CH4, and Fe3C have vital influence on the reaction.
• The pathways of Fe2O3 reacting with H2S were successfully established.
• The major route of the reaction mechanism is Fe2O3 reacting with H2S to form FeS.

This study aims to understand the roles of hydrogen and carbon monoxide during the desulfurization process in a coal gasification system that H2S of the syngas was removed by Fe2O3/SiO2 sorbents. The Fe2O3/SiO2 sorbents were prepared by incipient wetness impregnation. Through the breakthrough experiments and Fourier transform infrared spectroscopy analyses, the overall desulfurization mechanism of the Fe2O3/SiO2 sorbents was proposed in this study. The results show that the major reaction route is that Fe2O3 reacts with H2S to form FeS, and the existence of CO and H2 in the simulated gas significantly affects equilibrium concentrations of H2S and COS. The formation of COS occurs when the feeding gas is blended with CO and H2S, or CO2 and H2S. The pathways in the formation of products from the desulfurization process by the reaction of Fe2O3 with H2S have been successfully established.

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