Efficient mercury removal in chlorine-free flue gas by doping Cl into CuO nanocrystals.

The low content of hydrogen chloride (HCl) in flue gas is difficult to meet the request of Hg removal. Here, a small amount of Cl was doped into the crystal lattice of CuO nanocrystals (Cl-CuO), presenting excellent Hg removal efficiency in chlorine-free coal combustion flue gas. SEM, XRD, BET, and XPS characterizations revealed well crystal morphology and structure of Cl-CuO catalyst. Besides, Cl-CuO had smaller sizes and higher BET surface area compared with CuO. Hg removal behaviors were studied using a lab-scale fixed-bed reactor. After doping Cl, Hg removal efficiency was improved obviously and could reach nearly 100% above 150 ℃, indicating chlorine incorporated into the catalyst lattice had a better role for Hg removal. Besides, gas composition effect on Hg removal was analyzed. Cl-CuO had high sulfur resistance capacity, and Hg removal efficiency can still reach above 90% even at 2000 ppm SO. O played a critical role in the Hg removal reaction. Furthermore, a plausible mechanism for Hg removal was analyzed. Doping Cl into the lattice of CuO nanocrystals was beneficial for the activation of molecular oxygen, and generated reactive oxygen species can further activate Cl to participate in the Hg removal reaction.