Characterization of a regenerable sorbent for high temperature elemental mercury capture from flue gas

In this work we have developed a regenerable synthetic sorbent based on manganese oxides (12% w/w) impregnated on high surface area ?-alumina and supported as a thin layer (40?m) onto cordierite honeycomb monoliths (400cpsi), well suited for flow-through exhaust gas treatment associated with very low pressure drops. Elemental mercury capture experiments were carried out in a lab-scale quartz reactor in air at temperatures ranging from 50 to 350°C, Hg concentration in the range 50-250?g/m3, GHSV=3.6o105 h-1. A kinetic and capacity characterization of the sorbent was conducted, leading to the discrimination of the controlling mechanisms of the mercury capture process. Structured MnOx sorbent performed satisfactorily up to 300°C, the performance decaying dramatically above this temperature when desorption of elemental Hg becomes predominant. TPD experiments carried out after mercury uptake on the sorbent, showed that the sorbent could be completely regenerated at a temperature as low as 500°C. Repeated cycles of mercury adsorption/desorption did not lead to any significant reduction of the sorbent capacity towards mercury uptake. No significant mercury oxidation in the gas phase was observed under the operating conditions used in the experiments.