吸附相反应技术制备MnO_x/CeO_2/SiO_2催化剂及其低温选择性催化还原NO_x

采用吸附相反应技术制备得到了MnOx/CeO2/SiO2催化剂,通过X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、紫外激光拉曼(Raman)等手段对催化剂进行了表征.HRTEM分析表明活性组分MnOx与CeO2都均匀分布在载体SiO2表面;XRD分析表明Mn3O4特征峰随着CeO2含量的增加逐渐减小至完全消失,CeO2的加入降低了MnOx的结晶程度,增加了MnOx的分散性;Raman光谱表明催化剂表面的Mn离子能够进入CeO2晶格,激发出空穴氧,随着CeO2负载量的增加,催化剂氧空穴浓度先升高后降低.以NH3为还原剂,考评催化剂的NOx低温选择性催化还原(SCR)性能,催化剂催化活性随CeO2负载量增加先升高后降低,与催化剂氧空穴浓度变化规律一致,说明催化剂活性受氧空穴浓度影响,氧空穴浓度升高,催化剂催化活性升高.

MnOx/CeO2/SiO2 Catalysts Prepared by Adsorption Phase Reaction Technique for Selective Catalytic Reduction of NOx at Low-Temperature

MnO_x/CeO₂/SiO₂ catalysts were prepared by the adsorption phase reaction technique and were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. HRTEM showed that MnO_x and CeO₂ particles were uniformly coated on the surface of SiO₂. The XRD spectra showed that the intensity of the Mn₃O₄ diffraction peaks gradually decreased and then completely disappeared with the increasment of the CeO₂ content, which indicated that CeO₂ reduced the crystallinity of MnO_x and improved the dispersibility of MnO_x. Raman spectroscopy indicated that Mn ions on the surface of catalysts could enter into the lattice of CeO₂, replace oxygen ions, and form oxygen vacancies. With the increasment of CeO₂ content, the density of oxygen vacancies initially increased and then decreased. We used the catalysts for selective catalytic reduction (SCR) of NO_x with NH₃. The catalytic activity initially increased and then decreased with the increasment of CeO₂ content, similar to the change in the density of oxygen vacancies. Thus, the catalytic activity of the MnO_x/CeO₂/SiO₂ catalysts increases with increasing the density of oxygen vacancies.