论文部分内容阅读
采用γFe2O3纳米粉末制备选择性催化还原(selective catalysis reduction，SCR)脱硝催化剂，通过XRD、BET对催化剂进行表征，并对此催化剂的低温SCR脱硝性能在一固定床反应器中进行考察；此外通过原位红外漫反射光谱法(diffuse reflectance infrared Fourier transform spectroscopy， DRIFTS)研究了反应物在催化剂表面的吸附活化。结果表明，实验所采用的Fe2O3为纯γ相，具有较高的热稳定性和脱硝效率。DRIFTS实验研究表明，NH3主要吸附到γFe2O3催化剂表面 L 酸位形成吸附态的 NH3，在小于270℃时有部分NH3吸附到B酸位生成NH4+；O2的存在能促进吸附到L 酸位上的 NH3发生脱氢反应生成 NH2，并能够大大促进NO在催化剂表面吸附生成硝酸盐和吸附态的NO2，从而促进低温下的SCR反应。在90~360℃的温度区间内可能遵循两种反应途径，主要反应是吸附在L酸位的NH3脱氢生成NH2，然后和气态的NO反应生成N2和H2O；在低于240℃时，可能存在另外一种反应途径，中间产物 NO2(NH4+)2与NO反应生成N2、H2O和H+。“,”The catalyst used for selective catalysis reduction (SCR) of NOx was prepared from γFe2O3 nanoparticles and characterized by XRD and BET methods. The catalytic experiments at low temperature were carried out in a fixed bed reactor. The adsorption and activation of NH3 and NO on γFe2O3 nano-catalyst were investigated by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurement. Results showed that Fe2O3 used for catalytic reaction was pure maghemite phase with high thermal stability, and exhibited a high low-temperature denitration performance. The DRIFTS experiments showed that NH3 was mainly adsorbed on Lewis acid sites to form coordinated NH3, while partial NH3 was adsorbed on Br?nsted acid sites to form ammonium at the temperature below 270℃. O2 promoted the dehydrogenation of coordinated NH3 to form amide species. O2 greatly enhanced the adsorption of NO on catalysts surface to form nitrate species and absorbed NO2. Two possible reaction paths on γFe2O3 catalyst were proposed. The SCR process mainly follows that NH2 formed by H-abstraction of coordinated NH3 reactes with NO to form N2 and H2O. In a relative low temperature range (<240℃), another reaction path follows that NO2(NH4+)2 as the key intermediate product reactes with NO to form N2, H2O and H+.