Revealing the Key Role of Acidic Oxygen-Containing Groups on Activated Carbon for Low-Temperature NH3-SCR Denitration

Simultaneous desulfurization and denitration by using activated coke is one of the most competitive technologies for cleaning low-temperature steel flue gases. The key to denitration performance relies on the regulation of active groups on the catalyst. In this work, the carboxyl and lactone groups with (NH4)2S2O8 oxidation and thermal treatment were found to mainly determined the catalytic activity. The results showed that (NH4)2S2O8-treated AC catalyst improved denitration activity at low temperatures, which was attributed to the increase in oxygen-containing groups of the AC, the thermal treatment enhanced the low-temperature activity while reduced the performance in (210–240 ℃). According to the characterization results and conformational relationship analysis, we revealed that the adsorption and activation of NH3 mainly depended on carboxyl groups during the middle-temperature range (210–240 ℃) NH3–SCR. Based on the advantage of middle-temperature denitration activity of modified activated coke, the carboxyl groups on activated coke were the most important active sites for the NH3–SCR reaction. Moreover, lactone groups, improved the denitration performance via promoting NO oxidation at low-temperatures range (120–150 ℃). However, the presence of only lactone groups in the 210–240 ℃ is not beneficial for the further promotion for denitration activity. This work initially reveals the decisive role of carboxyl and lactones groups of activated coke for the low-temperature NH3-SCR reaction, and guides the industrial arrangement of oxidation-modified AC as denitration catalyst.