不同CuO/CeO_2催化剂上CO低温氧化反应

Low-Temperature CO Oxidation over Different CuO/CeO_2 Catalysts

分别用热解硝酸铈法和浸渍法制备了不同物性的CeO2粉体和相应的CuO/CeO2催化剂,并用XRD,HRTEM和TPR等对样品进行了表征,利用微反-色谱装置考察了其催化CO低温氧化的活性.结果表明,热解温度影响CeO2的物性(形貌、粒度大小及分布等).相同条件下,不同物性的CeO2载体上CuO的负载情况不同,500℃热解获得的CeO2载体上非晶态CuO负载量最高,相应的CuO/CeO2催化剂活性也较高.非晶态CuO一部分进入CeO2晶格,另一部分高度分散于CeO2表面上.焙烧温度较低时(≤600℃),催化剂活性受焙烧温度的影响较小,而高温(800℃)焙烧后,催化剂则因载体粒度增大和CuO烧结团聚等因素导致催化活性明显降低.

CeO2 particles with different physical properties were prepared by thermal decomposition of cerous nitrate and then used as supports for CuO/CeO2 catalysts （CuO content was 6.3% based on the CeO2 mass） prepared by impregnation method. The CeO2 particles and CuO/CeO2 catalysts were comparatively investigated by XRD, HRTEM and TPR measurements. The catalytic properties of the catalysts for low-temperature CO oxidation were studied by using a microreactor-GC system. The results showed that the thermal decomposition temperature affected the physical properties （such as morphology, particle size and distribution） of CeO2 particles. The loading of non-crystal CuO on the CeO2 supports was different and it was the highest on the CeO2 prepared by thermal decomposition at 500 ℃ , and the corresponding CuO/CeO2 catalysts exhibited higher activity for CO oxidation than those with CeO2 prepared by thermal decomposition at 400 and 700℃. A part of non-crystal CuO in CuO/CeO2 catalysts entered CeO2 lattice and the others dispersed over the CeO2 surface. When the calcination temperature was lower than 600 ℃ , it had little effect on the catalytic activity. However, high calcination temperature （e. g. 800 ℃ ） resulted in a significant impact on the catalytic activity because of CeO2 crystal growth and CuO aggregation.