LP/LIF study of the formation and consumption of mercury (I) chloride: kinetics of mercury chlorination

The laser photolysis/laser induced fluorescence (LP/LIF) technique has been applied to studies of gas-phase mercury (Hg) chlorination. Mercury (I) chloride (HgCl) was been detected via LIF at 272 nm from reactions of elemental Hg with Cl atoms generated from the 193 nm photolysis of carbon tetrachloride. While the formation of HgCl was too fast to be observed on millisecond time scales, the kinetics of the consumption of HgCl have been determined at temperatures characteristic of post-combustion conditions. Rate coefficients and Arrhenius parameters for the reaction of HgCl with Cl2, HCl and Cl atoms were determined. The reaction of HgCl with Cl2 was the fastest reaction studied, while the reaction of HgCl with HCl was the only reaction to show any measurable temperature dependence. Estimates of the rate coefficient for the reaction Hg + Cl --> HgCl were determined using a modeling approach. Comparisons of these new measurements with model predictions are discussed.