High-temperature cleaning for chlorine-containing coal gas by supported manganese oxide sorbent

This research aimed to achieve HCl removal for chlorine-containing hot coal gas by using supported oxide sorbents in a fixedbed reactor at 673-873 K. Mn₂O₃/SiO₂ was chosen as the optimal sorbent to eliminate chlorine species, after thermodynamic screening of the dechlorination potential of sorbents based upon various metals. The dechlorination experiments and results of the ICP, BET, XRD, XPS, and FTIR analyses provided in-depth views of the reaction chemistry behind the complex system of HCl removal in a simulated syngas containing 3,000 ppm HCl, 25 vol% CO, 15 vol% H₂, and N₂. When the sorbent composed of 23 wt% Mn₂O₃/SiO₂ came into contact with HCl, CO, and H₂, the reaction mechanism contained two paths. At lower temperatures Mn₂O₃ tended to react with HCl, while at higher temperatures it might first be reduced into Mn₃O₄ and then react with HCl. The probable products from the reaction (Mn₂O₃ and HCl or Mn₃O₄ and HCl) are MnCl₂, Cl₂, and H₂O. That is, as the reaction temperature increased, the second path started to become more important. The final product of this reaction might also include metallic manganese in addition to MnCl₂. Furthermore, when the temperature increased, the equilibrium constants of all the reactions reduced, and subsequently resulted in the decreasing sorbent performance.