Non-pitch coal-based activated coke introduced CeOx and/or MnOx for low temperature selective catalytic reduction of NOx by NH3

Abstract

Modified activated coke was prepared by introducing CeO_x and MnO_x on non-pitch coal-based activated coke (NPAC) using a novel non-pitch binder. Employing a fixed bed reactor and N₂ adsorption–desorption, X-ray diffraction, and X-ray photoelectron spectroscopy techniques, we investigated the changes of surface functional groups, pore structure characteristics, denitrification activity and adsorption behavior. It was also found that the presence of Ce³⁺ and Ce⁴⁺ species, promoting NO oxidation adsorption, significantly increased the starting denitrification activity and the catalysis of Mn species, helping NH₃ adsorption, showed a gradual increase in activity after a time delay. For co-impregnation modification of MnO_x and CeO_x, the manganese species and cerium species incorporated activated coke to formed cerium manganese carbide. With the increase in impregnation amount, the graphite crystalline structure was destroyed, causing the degree of graphitization to be reduced and the peak of Mn 2p_3/2 to be shifted to a lower binding energy. The addition of CeO_x played an important role in changing the existing state of the manganese oxide and adding MnO_x contributed to the oxidation of Ce³⁺ to Ce⁴⁺. On MnO_x–CeO_x-7.40 adsorbed NH₃ can react with adsorbed NO_x species (adsorbed NO₃ and NO₂) following a Langmuir–Hinshelwood mechanism. The denitrification rate of MnO_x–CeO_x-7.40 at 140 °C was as high as 75.36%.