分别用溶胶凝胶法和分步沉淀法制备了MnOx+γ-Al2O3和MnOx/γ-Al2O3,用等体积浸渍法将等量的Pd(NO3)2分别浸渍于其上,再将它们分别涂覆于堇青石上,得到不同物理化学性质的整体式催化剂,并采用X射线衍射、X射线光电子能谱、程序升温还原和低温N2吸附-脱附等技术对催化剂进行表征.结果表明,制备方法和MnOx焙烧温度明显影响催化剂中MnOx的物相、表面Mn物种和表面活性氧物种的分布及织构性质.活性测试结果表明,两种制备方法得到的催化剂于16-90 oC,380000-580000 h-1条件下均可将0.6µL·L-1 O3完全分解；尤其是溶胶凝胶法制备的Pd/γ-Al2O3+MnOx/γ-Al2O3催化剂分解O3活性较好,催化剂表面Mn2+：Mn3+：Mn4+=1.7：1：3(mol).%MnOx+γ-Al2O3 and MnOx/γ-Al2O3 catalysts were prepared by the sol-gel and sequential precipitation methods, respectively. The same amount of Pd was loaded on these catalysts by incipient wetness impregnation. The two Pd-MnOx/γ-Al2O3 catalysts with different physicochemical properties were coated on cordierite. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, and N2 adsorption-desorption measurement. The preparation method and calcination temperature of MnOx have significant impact on the crys-talline phase of MnOx, MnOx species and active oxygen species, and textural properties of the cata-lysts. The experimental results showed that 0.60 µL∙L-1 of ozone was completely decomposed on these catalysts in the temperature range of 16 to 90 °C at space velocities from 380000 to 580000 h-1. In particular, the activity for O3 decomposition was excellent on the Pd/MnOx+Pd/γ-Al2O3 cata-lyst that used MnOx prepared by the sol-gel method. Mnn+is beneficial for O3 decomposition, and Mn2+, Mn3+, and Mn4+were presented in a mole ratio of 1.7:1:3 on the surface of the catalyst.
展开▼
