The Mn2O3/SiO2 sorbent prepared by incipient wetness impregnation was investigated for the elimination of chlorine species produced from coal gasification. The experiments were conducted in a fixed-bed reactor at 673 K with the Mn2O3/SiO2 sorbent at various CO and H2 concentrations to evaluate their influences on the dechlorination performance. It was observed that the absence of inlet H2 led to a drastic decrease in the sorbent capacity; i.e., the presence of H2 was essential for achieving dechlorination. Furthermore, the concentration of CO seemed to have no obvious effect on the HCl removal.
Through the breakthrough experiments, X-ray powder diffractometer, and Fourier transform infrared spectroscopy analysis, the overall dechlorination mechanism of the Mn2O3/SiO2 sorbent in a chlorine-containing coal gas system was successfully described in this study. The mechanism consisted of three major routes: (a) Mn2O3 reacted with HCl to form MnCl2, (b) Mn2O3 was first reduced into Mn3O4 and then reacted with HCl to produce MnCl2, and (c) without the involvement of HCl in the dechlorination experiments, the Mn2O3 contained in the fresh sorbent was first reduced to Mn3O4 and then to MnO under the strong reducing atmosphere provided by CO and/or H2.