Understanding of the high hydrothermal stability of a catalyst prepared from Mn slag for low-temperature selective catalytic reduction of NO.

Manganese slag is a hazardous waste, which lacks proper treatment. For the first time, an effective catalyst for selective catalytic reduction of nitric oxide was synthesized from manganese slag by a sol-gel method. The obtained catalyst had an excellent low-temperature activity and high hydrothermal stability. It removed 46.3% of nitric oxide (990 ppm) at a temperature as low as 100 °C; its removal increased to 100% at 220 °C, which lasted for more than 2000 min. Moreover, hydrothermal treatment at 400 °C showed little influence on its activity. Even after hydrothermal treatment at 900 °C, the catalyst still removed 39.7% of NO at 220 °C, 22.7% higher than another catalyst synthesized from pure reagents. The hydrothermal stability was attributed to an amorphous layer of MnSiO. This layer covered the catalyst surface, protected active metal species, pore size and pore volume from steam attacking. Manganese slag thus realized the high-value-added utilization by synthesizing a catalyst with the high hydrothermal stability.