The adsorption and catalytic oxidation of the element mercury over cobalt modified Ce-ZrO2 catalyst

摘要

Co was used as a modifier for Ce-ZrO2 to improve the surface physicochemical properties of the catalysts. The obtained catalysts Co-x-Ce-ZrO2 were investigated for Hg-0 adsorption and oxidation in the temperature range of 100-350 degrees C. The results showed that Co modified catalysts had an excellent Hg-0 removal efficiency. For Co-0.3-Ce-ZrO2, the Hg-0 adsorption efficiency was above 81.5% even after a 164.5 h adsorption test and the Hg-0 oxidation efficiency reached 100% in the temperature range of 100-250 degrees C. XRD, BET and XPS results suggested that the Co modified catalysts had larger surface areas and more oxygen vacancies. H-2-TPR results showed that Co addition improved the redox performance of the catalyst. These results led to a better Hg-0 removal efficiency by the Co modified catalysts. Furthermore, XPS results of Co-0.3-Ce-ZrO2 before and after reaction showed that, during the Hg-0 oxidation process, surface chemisorbed oxygen was dramatically consumed while some Co3+ and Ce4+ changed to Co2+ and Ce3+. This suggested that chemisorbed oxygen participated in the Hg-0 oxidation process. A probable pathway of Hg-0 oxidation was deduced based on these results. The effects of individual flue gas components (O-2, NO, H2O, SO2) on Hg-0 oxidation efficiency were investigated and the results showed that O-2 and NO improved the Hg-0 oxidation efficiency whereas H2O and SO2 inhibited it.