Enhancing the effect of CoAl2O4 on the simultaneous removal of H2S and NH3 on Co- and Mo- based catal-sorbents in IGCC

Co-Mo-based catal-sorbents were prepared on various supports, such as Al2O3 (CMA), SiO2 (CMS), and ZrO2 (CMZ), by an impregnation method, and were tested for the simultaneous removal of H2S and NH3 gases in a fixed bed reactor. Similar sulfur removal capacities were obtained for all the catal-sorbents in the presence of NH3 gas at 650 °C. However, only CMA catal-sorbent had an excellent NH3 decomposition ability during the H2S absorption. All of the catal-sorbents formed CoMoO4, which was the main active site for H2S absorption. In particular, CoAl2O4 was only observed in the CMA catal-sorbent, and it was reduced by NH3 at low temperatures, a phenomenon that improved the NH3 decomposition ability of the catal-sorbent during the H2S absorption process. To improve the simultaneous removal ability of Co-Mo-based catal-sorbents for H2S and NH3, aluminum-promoted Co-Mo-Al-based catal-sorbents (CMAS and CMAZ) were prepared by a new-impregnation method and examined. The NH3 decomposition ability of the CMAS and CMAZ catal-sorbents increased during multiple cycles compared to that of the CMS and CMZ catal-sorbents. Furthermore, the simultaneous removal efficiencies of CMAS, and CMAZ for NH3 and H2S were maintained over multiple cycles.