Application of gold catalyst for mercury oxidation by chlorine.

This paper discusses a recent study of mercury catalytic oxidation by chlorinating reagents. Gold was chosen as the catalyst because of its reluctance to chemisorb some gases such as O2, NO, H2O, and SO2. This property, as demonstrated in this study, is instrumental to mercury oxidation by circumventing some undesired inhibitory reactions such as OH + NO + M --> HONO + M and OH + SO2 + M --> HOSO2 + M, which were recognized under homogeneous situations at high temperatures. In comparison to Cl2, HCl showed weak oxidizing capability but appreciable inhibition in mercury oxidation by Cl2, probably through the competition of active sites with Cl2. Overall, the mercury catalytic oxidation by Cl2 on gold catalyst surfaces was viable, reaching 40-60% in this study under temperatures of 448-498 K, where the thermal decomposition of formed Hg2+ was effectively avoided.