Effects of CO2 on the low-temperature NH3-SCR performance of CeOx-biochar catalyst

Low-temperature NH 3 -SCR of NO x technology was recognized as a promising way to control NO x emissions from industrial kilns at low temperatures. Except for SO 2 and H 2 O, lots of CO 2 exist in the flue gas of industrial kilns. However, there are few researches on the effects of CO 2 on the low-temperature NH 3 -SCR activity. To investigate the effects of CO 2 on the low-temperature NH 3 -SCR performance and mechanism of CeO x -biochar catalyst, a series of experiments employed. The results showed that the presence of CO 2 had an obvious inhibitory effect on the NH 3 -SCR performance of CeO x -biochar 0.6 at 150 °C. There was competitive adsorption between CO 2 and NO on the surface of CeO x -biochar 0.6 . CO 2 was mainly adsorbed on CeO 2 , which hindered the oxidation of NO and the adsorption of NO x on the catalyst surface. Meanwhile, although the presence of CO 2 could improve NH 3 adsorption capacity of CeO x -biochar 0.6 due to the formation of NH 4 HCO 3 and (NH 4 ) 2 CO 3 , the existence of carbonates and bicarbonates blocked the formation of active intermediates NH 4 NO 2 and NH 2 NO for NH 3 -SCR reaction. As a result, the NO x conversion of CeO x -biochar 0.6 was dropped from 96.9% to 40.8% at 200 °C. In view of the bicarbonate and carbonate species was unstable at high temperatures, the inhibitory effect of CO 2 on NH 3 -SCR reaction was gradually weakened with the increase of reaction temperature. The NH 3 -SCR activity of CeO x -biochar 0.6 was seldom affected by CO 2 at 300 °C. Finally, a CO 2 poisoning mechanism for NO x removal by NH 3 -SCR at low temperature was proposed.