CeO2对Pt/TiO2-Al2O3催化剂氧化及抗老化性能的影响

CeO_2 Effect on Oxidation and Anti-Aging Performance of Pt/TiO_2-Al_2O_3 Catalyst

Pt/TiO_2-Al_2O_3对CO,HC以及NOx均有较好的催化氧化活性,但钛铝载体在高温下易发生相变,导致Pt团聚烧结而失活,CeO_2作为助剂可与贵金属发生电子间作用,提高其抗老化性能。通过分步负载的方法,采用浸渍法先对钛铝载体负载不同质量分数的CeO_2,烘干后再对其二次浸渍,负载0.7%(质量分数)的Pt,考查CeO_2负载量对催化剂催化氧化活性的影响,由此筛选出性能较好的催化剂,在1000℃条件下进行老化处理,对比老化前后其物理化学性质以及催化性能,最后对催化剂老化样进行了物相分析。结果表明负载1%(质量分数)的CeO_2不但可以提高催化剂对CO和C_3H_6的氧化活性,而且显著改善了催化剂的抗老化性能,老化样的NO_2最大生成量可达112×10^(-6),较未添加CeO_2的催化剂老化样增加了23×10^(-6),且其温度窗口更宽,说明CeO_2作为Pt/TiO_2-Al_2O_3催化剂助剂有很大的潜在应用价值。

Pt/TiO2-Al2O3 catalyst had better activity than others for CO, HC and NOx oxidation, but at high temperature, TiO2-Al2O3 carrier was prone to phase transition, which easily led to the inactivation caused by Pt aggregation and sintering. As an additive, CeO2 could improve the aging resistance performance of the catalyst by electronic effect with precious metals. Using the stepwise im- pregnation method , different mass fractions of CeO2 were supported on the surface of TiO2-Al2O3 carrier firstly; after drying, 0.7% （ mass fraction） Pt was also supported with the method of impregnation on each sample. The effect of CeO~ loading amount on the cata- lytic oxidation activity was investigated, then the catalysts with excellent performance were selected and aged at 1000 ℃. After aging, the physical and chemical properties as well as the catalytic performance of the aged samples were compared with the fresh samples. Last, the phase analysis of the aged samples was carried out. The results showed that supporting 1% （mass fraction） CeOz could not only improve the oxidation activity for CO and C3 H6, but also significantly improve the anti-aging performance of the catalyst; the maxi- mum generation of NO2 reached 112 ×10 -6 under the aged sample, which increased by 23 × 10 -6 compared to the aged catalyst without CeO2, and the temperature window was wilder. The result indicated that CeO2 possessed a great potential as an additive in Pt/TiO2- Al2O3 catalyst.