The homogeneous gas phase reaction of mercury with oxygen, and the corresponding heterogeneous reactions in the presence of activated carbon and fly ash

A laboratory-scale stopped flow reactor was used to study the homogeneous gas phase reaction of elemental mercury with oxygen and the corresponding heterogeneous reaction in the presence of activated carbon and fly ash at different temperatures. No homogeneous gas phase reaction occurred during a reaction time of 1 hour in the temperature range 20–700°C. An upper limit second order rate constant of 1•10−23 cm3 molec.−1 s−1 at 20°C and 4•10–23 cm3 molec.−1 s−1 at 700°C, was estimated. In the presence of activated carbon or fly ash, at temperatures of 100–300°C, mercury loss increases with increasing oxygen concentration. The reaction rate has a maximum at 200–250°C, and exhibits a half order oxygen dependence and a fast order dependence with respect to mercury.