Simultaneous removal of SO2 and NOx from flue gas using a CuO/Al2O3 catalyst sorbent: I. Deactivation of SCR activity by SO2 at low temperatures

Deactivating effect of SO2 on selective catalytic reduction of NO by NH3 over a CuO/Al2O3 catalyst sorbent was examined in a fixed-bed reactor. Transient experiment, DRIFT, elemental analysis, temperature-programmed techniques, and physical adsorption were used to evaluate the deactivation mechanism. Results show that SO2 greatly deactivates SCR activity of CuO/Al2O3 catalyst sorbent at temperatures of 200–300 °C, and the deactivation is dependent on reaction temperature. The deactivating agents are ammonium sulfate salt and copper sulfate, formed during the reaction of NO–NH3–O2–H2O in the presence of SO2. Ammonium sulfate salt reduces the SCR reaction through pore filling and/or plugging, but can be removed by heat treatment at around 400 °C. Copper sulfate deactivates the SCR either by pore filling and/or plugging or by its low SCR activity compared to CuO at low temperatures. Copper sulfate decomposes at temperatures greater than 660 °C but can be converted back to CuO in NH3 at about 400 °C.