Growing concern over mercury emissions to air from power generation e.g. from coal and biomass has led to some local and national limits being imposed. One of the benefits of SCR is that the mercury can be oxidised in the presence of a halide such as chlorine or bromine. The reaction mechanism is thought to follow an Eley Rideal type where:
- The mercury (Hg) adsorbs at the Vanadium (V) Oxide (O) active site creating a V-Hg-O site.
- Hydrogen Chloride (HCl) reacts with the adsorbed Hg generating the oxidised Hg which diffuses into the gas.
The mercury chloride is then removed downstream in the scrubber.