Pt-Ir/γ-Al_2O_3(SiO_2)模型重整催化剂表面特性的研究

SURFACE CHARACTERISTICS OF MODEL REFORMING CATALYST Pt-Ir/γ-AI_2O_3(SiO_2)

通过X射线光电子能谱和俄歇电子能谱对氧化(350℃,空气中)和还原(480℃氢气流中)状态的Pt—Ir/γ—Al_2O_3和Pt—Ir/SiO_2模型催化剂的表面特征进行了研究。试验发现,氧化状态下,样品表面上主要是PtO_2和Ir的高价氧化物以及少量PtO,还原过程使这些氧化物转化为金属,主要是以微细的金属簇的形式分散在表面上。Pt和Ir之间存在相互作用,是形成双金属簇的表现,同时还有少量由于金属烧结过程形成的较大的金属粒子,该状态下的Pt_(4f)和Ir_(4f)结合能较前者略低;SiO_2载体上的铂和铱的原子浓度与在γ—Al_20_3上有明显差异。

X-ray photoelectron spectroscopy for chemical analysis and Auger electron spectroscopy were used for characterizing thing surfacing of model Pt-Ir/ Al2O3(SiO2) catalyst after oxidation in air at 350℃ and reduction in hydrogen at 1 atm and 480℃. Results showed that reduction converted PtO2, PtO and oxide of higher valence iridum present on the surface of oxided sample to bimetallic clustes and a small amount of larger or bulk-like particles in sintering. The properties of support obviously affect the atomic concentration of supported metals and Pt4f and Ir4f binding energy of metallic platinum and irdium.