Hongyun Yang and Bruce J. Tatarchuk. Chemical Engineering, Auburn University, 207 Ross Hall, Auburn, AL 36849
Zinc oxide (ZnO) is a widely used sorbent for H2S removal at low temperatures, ca. 400 °C. In this study, nine different transition metal doped ZnO sorbents were prepared and loaded on SiO2 particles (100-200 µm) by incipient wetness impregnation for H2S removal at stack temperatures of PEM fuel cells. The results of desulfurization tests on these sorbents at room temperature indicates that a copper doped ZnO/SiO2 sorbent (Cu-ZnO/SiO2) had the highest saturation sulfur capacity at 0.213 g sulfur/g ZnO (54% of the theoretical capacity) which was two times higher than that of ZnO/SiO2 sorbent at room temperature. In these experiments, CO2, CO and water did not demonstrate significant effects on the desulfurization performance of Cu-ZnO/SiO2. The addition of copper to ZnO/SiO2 made the sorbents more sensitive to desulfurization temperature in a low temperature range of 100-250 °C. Compared with a widely used commercial ZnO sorbents, ZnO/SiO2 and Cu-ZnO/SiO2 were highly regenerable. Cu-ZnO/SiO2 can be regenerated at a low regeneration temperature, ca. 300 °C, which is 200-300 °C lower than these of ZnO/SiO2 and the commercial sorbent. The microfibrous entrapped Cu-ZnO/SiO2 sorbent can be applied as an inline filter to protect the fuel cell from sulfur poisoning.