Cobalt-modified limonite catalyst for low temperature selective catalytic reduction of NOx in ore sintering flue gas by NH3

Abstract

Natural limonite possesses characteristics of rich reserves and low sintering efficiency. In this study, the Co/Limonite composites were prepared through a one-step impregnation method by using limonite as a precursor and cobalt oxide as a modifier. The influence of cobalt doping amount and calcination temperature on the denitrification efficiency over the composite were investigated. The results showed that the Co/Limonite composite was the optimum over Co/Fe mass ratio of 0.06 and the calcination temperature of 350 °C, it exhibited an excellent low-temperature catalytic activity, stability and good resistance to H2O(g) and SO2. When NO initial concentration was 500 ppm, gas hourly space velocity (GHSV) was 36,000 h−1 and reaction temperature was 100 ℃, the denitrification efficiency reached 100%. Adding of 10 vol% H2O(g) or 50 ppm SO2, respectively, the denitrification efficiency was about 90% at reaction temperature was 150 ℃, while it could approach to 80% with H2O(g) and SO2 were added simultaneously. The micromorphology and physicochemical properties of the catalysts were analyzed by systematic characterization techniques. The Limonite could obtain more surface acid sites and larger adsorption capacity by cobalt modification. More Lewis acids and weak Brønsted acids could greatly contribute to improve the low temperatures denitrification catalytic activity.