纺锤型CuO/CeO_2催化剂CO还原NO催化性能的研究

Investigation of catalytic performance of CuO/CeO_2 spindle catalysts

水热法合成纺锤型CeO_2载体,再通过浸渍法制备纺锤型CuO/CeO_2催化剂。采用X射线衍射(XRD)、N2吸附—脱附、扫描电镜(SEM)、高分辨透射电镜(HRTEM)、程序升温还原(H2-TPR)、程序升温脱附(O2-TPD)对样品进行表征。以CO+NO为反应模型并研究其催化性能。考察不同CuO负载量在纺锤型CeO_2载体上的分散性及其CuO/CeO_2催化剂的催化活性。结果表明:CuO负载量小于9%时,CuO均匀分散在载体表面,且样品比表面积,Ce3+和氧空位的量都随着CuO的量增大而增大。当CuO的负载量为9%时,高度分散在载体表面的CuO活性组分最多,比表面积、Ce3+和氧空位的量最大,还原性最强,因此催化CO+NO的催化性能最好。在290℃时,其NO的转化率、N2选择性、N2收率都能达到100%。但当负载量大于9%时,由于过量的CuO聚集成大颗粒的CuO分子簇覆盖在载体表面,导致分散在载体表面的CuO活性组分减少,比表面积减小,还原性能降低,CO还原NO的催化性能降低。

The CeO2 spindle supports were prepared by hydrothermal method,and then the CuO /CeO2 spindle catalysts were synthesized using impregnation method. The catalysts were characterized by X-ray diffraction（ XRD）,N2 absorption-desorption,scanning electron microscope（ SEM）,high resolution transmission electron microscope（ HRTEM）,temperature programmed reduction of H2（ H2-TPR）,and temperature-programmed desorption of O2（ O2-TPD）. The catalytic performances of catalysts were evaluated by CO ＋ NO model reaction. The dispersion capacity of different amount of CuO on the CeO2 spindle supports and the catalytic performance of CuO / CeO2 spindle cat-alysts were studied. The results indicated that CuO were highly dispersed on catalyst surface until the loading amount of copper was up to 9%,the specific surface area,the amount of Ce3＋and oxygen vacancy increased with the increasing of CuO amount. When the loading amount of CuO was 9%,the catalysts had the most the active component CuO with high dispersion on the surface,high specific surface area,excellent reduction ability,and more oxygen vacancies. Thus,9% CuO / CeO2 was of the best catalytic performance. The NO conversion,N2 selectivity,and N2 yield of 9% CuO /CeO2 reached 100% at 290 ℃. With further increasing loading amount of CuO,excessive CuO aggregated to form large particles of CuO species and covered the surface of the CuO / CeO2 catalysts,resulting in decrease of the specific surface area and the reducibility.