Efficient mercury removal in chlorine-free flue gas by doping Cl into Cu2O nanocrystals

The low content of hydrogen chloride (HCl) in flue gas is difficult to meet the request of Hg-0 removal. Here, a small amount of Cl was doped into the crystal lattice of Cu2O nanocrystals (Cl-Cu2O), presenting excellent Hg-0 removal efficiency in chlorine-free coal combustion flue gas. SEM, XRD, BET, and XPS characterizations revealed well crystal morphology and structure of Cl-Cu2O catalyst. Besides, Cl-Cu2O had smaller sizes and higher BET surface area compared with Cu2O. Hg-0 removal behaviors were studied using a lab-scale fixed-bed reactor. After doping Cl, Hg-0 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-0 removal. Besides, gas composition effect on Hg-0 removal was analyzed. Cl-Cu2O had high sulfur resistance capacity, and Hg-0 removal efficiency can still reach above 90% even at 2000 ppm SO2. O-2 played a critical role in the Hg-0 removal reaction. Furthermore, a plausible mechanism for Hg-0 removal was analyzed. Doping Cl into the lattice of Cu2O nanocrystals was beneficial for the activation of molecular oxygen, and generated reactive oxygen species can further activate Cl to participate in the Hg-0 removal reaction.