Simultaneous removal of NOx and Hg0 from simulated flue gas over CuaCebZrcO3/r-Al2O3 catalysts at low temperatures: performance, characterization, and mechanism

To optimize the simultaneous removal of NO x and Hg 0 , a series of Cu a Ce b Zr c O 3 /γ-Al 2 O 3 catalysts prepared by the impregnation method were explored and their physical and chemical properties were analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), NH 3 -temperature-programmed desorption (NH 3 -TPD), H 2 -temperature-programmed reduction (H 2 -TPR), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFT), and Fourier transform infrared spectroscopy (FT-IR). The results showed that 15% Cu 1.4 Ce 0.55 Zr 0.25 O 3 /γ-Al 2 O 3 resulted in the highest conversion efficiency for the simultaneous removal of NO x (93%) and Hg 0 (85%) at low temperatures (200 to 300 °C). Meanwhile, 15% Cu 1.4 Ce 0.55 Zr 0.25 O 3 /γ-Al 2 O 3 showed good stability and resistance to SO 2 and H 2 O, which is due to its low crystallinity, good textural performance, and strong redox ability. According to the TPD, TPR, and XPS results, the strong acidic character of 15% Cu 1.4 Ce 0.55 Zr 0.25 O 3 /γ-Al 2 O 3 promoted the removal of NO x and Hg 0 . The synergistic effect between CuO and CeO 2 in 15% Cu 1.4 Ce 0.55 Zr 0.25 O 3 /γ-Al 2 O 3 can increase the mobility of chemically adsorbed oxygen and activates lattice oxygen, leading to an excellent performance. The DRIFT results showed that NH 3 , NH 4 + , nitrate, and nitrite participated in the selective catalytic reduction (SCR) reaction. On the basis of our experimental results, Hg 0 and NO x removal mechanisms were proposed as Hg (ad) + O* → HgO (ad) and 2NH 3 /NH 4 + (ad) + NO 2 /NO 3 − (ad) + NO→2N 2 + 3H 2 O/2H + , respectively.