Mn-Cr mixed oxide adsorbents with high SO2 resistance for elemental mercury removal from coal-fired flue gas

A series of Mn-Cr mixed oxide adsorbents were obtained using co-precipitation method. Then, an inves-tigation was conducted into the effects of Mn/Cr molar ratio, reaction temperature, calcination temper-ature, initial mercury concentration and flue gas constituents on the outcome of elemental mercury removal. Specifically, the MnCr1:3 with an optimal Mn/Cr molar ratio performed best in the efficiency of mercury removal (>95.4%) in a wide temperature range (100-250 degrees C). The physicochemical properties and the mechanism were characterized by N2 adsorption-desorption, SEM, XRD, NH3-TPD, H2-TPR, XPS and Hg-TPD in combination. According to the research results, mercury removal was facilitated by MnCr1:3 due to its larger surface area, smaller crystallite sizes, higher acidity and redox properties. Sulfur dioxide promoted elemental mercury capture for MnCr1:3 when different concentrations of SO2 existed in the flue gas. The relative activity over MnCr1:3 approached 100% after five regeneration cycles. Due to the combined effect of manganese and chromium, there was an increase in the concentration of high valence metal elements and surface adsorbed oxygen. MnCr1:3 had the highest content of Cr6+ and adsorbed oxygen species, for which they played a vital role in the outcome of mercury removal.(c) 2023 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

A series of Mn-Cr mixed oxide adsorbents were synthesized using co-precipitation method. The effects of Mn/Cr molar ratio, reaction temperature, calcination temperature, initial mercury concentration, and flue gas constituents on mercury removal were investigated. MnCr1:3 with an optimal Mn/Cr molar ratio showed the highest efficiency (>95.4%) in a wide temperature range (100-250 degrees C) for mercury removal. The physicochemical properties and mechanism were characterized using various techniques. MnCr1:3 facilitated mercury removal due to its larger surface area, smaller crystallite sizes, higher acidity, and redox properties. Sulfur dioxide promoted elemental mercury capture for MnCr1:3. After five regeneration cycles, MnCr1:3 maintained a relative activity of 100%. The combined effect of manganese and chromium resulted in an increase in high valence metal elements and surface adsorbed oxygen, which played a vital role in mercury removal.