Simultaneous removal of SO 2 and NO x from flue gas using a CuO/Al 2O 3 catalyst sorbent : I. Deactivation of SCR activity by SO 2 at low temperatures

Abstract

Deactivating effect of SO 2 on selective catalytic reduction of NO by NH 3 over a CuO/Al 2O 3 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 SO 2 greatly deactivates SCR activity of CuO/Al 2O 3 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–NH 3–O 2–H 2O in the presence of SO 2. 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 NH 3 at about 400 °C.