Pt/CexZr1-xO2催化剂上丙烷完全氧化性能研究

采用沉淀法制备了ZrO2,CeO2和Ce0.7Zr0.3O2载体,并用浸渍法制备负载型Pt催化剂。考察了500和900℃焙烧催化剂的丙烷完全氧化性能和水汽对丙烷氧化反应的影响。对于500℃焙烧的催化剂,催化剂的丙烷氧化活性顺序为:Pt/ZrO2-500>Pt/CeO2-500>Pt/Ce0.7Zr0.3O2-500;而经900℃焙烧的催化剂活性顺序为:Pt/ZrO2-900>Pt/Ce0.7Zr0.3O2-900>Pt/CeO2-900。反应气氛中水汽的存在对两种Pt/ZrO2催化剂的活性均有抑制作用(T50温度均提高了10~15℃);而对于Pt/CeO2-500催化剂有抑制作用(T50温度提高10℃),但对Pt/CeO2-900催化剂活性有促进作用(T50温度下降25℃);对于两种Pt/Ce0.7Zr0.3O2催化剂活性具有促进作用(T50温度均下降5~25℃)。表征结果表明催化剂的活性与其表面Pt物种价态密切相关,催化剂表面上Pt0物种有利于活性的提高。Pt/Ce0.7Zr0.3O2-500催化剂中只含有氧化态Pt物种(Pt^2+),而Pt/Ce0.7Zr0.3O2-900催化剂中则含有部分金属态Pt物种,因此其活性高于Pt/Ce0.7Zr0.3O2-500催化剂。

Pt/CexZr1-xO2 Catalysts for Total Oxidation of Propane

Three supports(ZrO2,CeO2 and Ce0.7Zr0.3O2)were prepared using a precipitation method,and supported Pt catalysts were prepared using an impregnation method.These catalysts were tested for total oxidation of propane and the effects of water vapor on the catalytic behaviors were investigated.For the catalysts calcined at 500℃,the activities followed an order of Pt/ZrO2-500>Pt/CeO2-500>Pt/Ce0.7Zr0.3O2-500.For those calcined at 900℃,the activities followed an order of Pt/ZrO2-900>Pt/Ce0.7Zr0.3O2-900>Pt/CeO2-900.When 2.5 vol.%water vapor was added in the feed stream,the activities of the Pt/ZrO2 catalysts were suppressed(with the T50 increased by 10~25℃);the activity of the Pt/CeO2-500 was suppressed(with the T50 increased by 10℃)while that of the Pt/CeO2-900 was improved(with the T50 decreased by 25℃);the activities of the Pt/Ce0.7Zr0.3O2 catalysts were improved(with the T50 decreased by 5~25℃).It is concluded that the presence of metallic Pt species is beneficial to the improvement of catalytic activity.The Pt/Ce0.7Zr0.3O2-500 catalyst contains exclusively oxidized surface Pt species(Pt^2+)while the Pt/Ce0.7Zr0.3O2-900 catalyst contains some metallic surface Pt species,which explains the improved activity observed on the Pt/Ce0.7Zr0.3O2-900.