γ射线辐照超细铂催化剂的载体效应

SUPPORT EFFECT OF ULTRAFINE PLATINUM CATALYSTS PREPARED BY γ RAY RADIATION METHOD

用γ射线辐射法制备了铂溶胶和粒径为５ｎｍ的超细铂粉，采用机械混合法和溶胶凝胶法制备了一系列不同载体的超细铂催化剂．不同载体对提高ＣＯ氧化活性的顺序为：ＭｇＯ＞γＡｌ２Ｏ３≥ＺｒＯ２＞ＴｉＯ２＞ＳｉＯ２．其中，由溶胶凝胶法制备的０１％Ｐｔ／ＳｉＯ２和０１％Ｐｔ／ＴｉＯ２的比表面积大，Ｐｔ分散度高，但活性最差．ＸＰＳ结果表明，部分表面Ｐｔ０和ＴｉＯ２作用生成了ＰｔＯ和Ｔｉ２Ｏ３，并且Ｐｔ的分散度愈高，Ｐｔ和ＴｉＯ２间的作用愈强，从而降低了ＣＯ氧化活性．而ＭｇＯ负载的超细铂样品活性明显高于常规浸渍法所制样品．ＸＰＳ结果表明，超细Ｐｔ／ＭｇＯ表面上存在大量的化学吸附氧，这可能是ＭｇＯ负载样品活性高的重要原因．

Ultrafine platinum supported on a variety of metal oxides was prepared by the γ radiation method. The support effect of the 0 1%Pt/MO x prepared by mechanical mixing of ultrafine Pt and support on the CO oxidation activity has the sequence of MgO> γ Al 2O 3 α Al 2O 3≥ZrO 2>TiO 2>SiO 2. Although the 0 1%Pt/SiO 2 and 0 1%Pt/TiO 2 prepared with ultrafine Pt by sol gel procedure possess high specific surface area and high dispersion, their activity is the lowest. It is identified by XPS measurement that some PtO and Ti 2O 3 formed from Pt and TiO 2. In contrast to the Pt/TiO 2, the ultrafine Pt/MgO sample shows obviously higher activity than that prepared by the impregnation method. A large amount of chemisorbed oxygen is found on the ultrafine Pt/MgO catalyst and this is the main reason for its high activity.