Effects of Co2 On the Low-Temperature Nh3-Scr Performance of CEO X -Biochar Catalyst

Abstract

The effects of CO2 on the low-temperature NH3-SCR activity of CeOx-biochar catalyst were investigated by a series of experiments, including activity test, X-Ray Diffraction (XRD), thermogravimetry (TG), temperature-programmed desorption (TPD) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results showed that the presence of CO2 had an obvious inhibitory effect on the NH3-SCR performance of CeOx-biochar at 150 °C. According to the DRIFTS and TPD results, there was competitive adsorption between CO2 and NO on the surface of CeOx-biochar. CO2 was mainly adsorbed on CeO2, which hindered the oxidation of NO and the adsorption of NOx on the catalyst surface. Meanwhile, although the presence of CO2 could improve NH3 adsorption capacity of CeOx-biochar due to the formation of NH4HCO3 and (NH4)2CO3, the existence of NH4HCO3 and (NH4)2CO3 blocked the formation of active intermediates NH4NO2 and NH2NO for NH3-SCR reaction. As a result, the presence of CO2 in the feed gas reduced the NOx conversion of CeOx-biochar at 150 °C. In view of the bicarbonate and carbonate species was unstable at high temperature, the inhibitory effect of CO2 on NH3-SCR reaction was gradually weakened with the increase of reaction temperature. Thus, the NH3-SCR activity of CeOx-biochar was seldom affected by CO2 at 300 °C. The research outcomes provide a guideline for understanding the impacts of CO2 on the low-temperature NH3-SCR of NOx.

Keywords: Biochar catalyst, CeO2, CO2, Reaction mechanism, Nitrogen oxide