Pt金属簇-聚苄基醚型树枝状分子复合物的制备及其催化性能

Preparation and Catalysis of Pt Metal Cluster Core-Polyaryl Ether Dendrimer Shell Nanocomposite

在乙醇水溶液中以聚苄基醚三乙酸氯化铵(G_3-NACl)为稳定剂制备了 Pt 金属簇(G_3-NACl-Pt)。通过透射电子显微镜、X 射线粉末衍射、傅里叶变换红外光谱和紫外可见光谱等方法对 G_3-NACl-Pt 进行了表征。改变原料 H_2PtCl_6与 G_3-NACl的摩尔比,制备的 G_3-NACl_-Pt 的平均粒径为2.0～5.5 nm;当 n(H_2PtCl_6)∶n(G_3-NACl)≤30时,G_3-NACl-Pt 具有很好的稳定性;n(H_2PtCl_6)∶n(G_3-NACl)=60所制得的 G_3-NACl-Pt 放置数周后发生聚沉。以 G_3-NACl-Pt 为催化剂考察了催化邻硝基苯甲醚加氢反应的活性,结果表明,G_3-NACl-Pt 催化剂中 n(Pt)∶n(G_3-NACl)=30时,在 n(邻硝基苯甲醚)∶n(G_3-NACl-Pt)=900、H_2气氛、反应温度40℃的条件下、反应3.5 h 时邻硝基苯甲醚的转化率大于99%。G_3-NACl-Pt 催化剂的重复使用实验结果表明,G_3-NACl-Pt 可重复使用,重复使用后催化加氢活性没有明显降低。

Pt metal cluster stabilized by polyaryl ether trisacetic acid ammonium chloride dendrimer of third generation （G3-NAC1-Pt）was prepared in a aqueous ethanol solution by using polyaryl ether trisacetic acid ammonium chloride dendrimer of third generation （G3-NAC1） as stabilizer. The obtained G3-NAC1-Pt was characterized by means of TEM, XRD, FTIR and UV-Vis. The average particle size of G3-NAC1-Pt is of 2.0 - 5.5 nm depending on mole ratio of H2 PtC16 to G3-NAC1. Pt metal cluster demonstrates to be nearly-monodispersed when n （Pt） ： n （G3-NAC1） in G3-NAC1-Pt is below 30. The colloidal solution of Pt metal cluster stabilized by the dendrimer, in which mole ratio of H2PtC16 and G3-NAC1 is less than 60, remains stable without precipitation for several weeks. The dendrons attach to Pt metal core radially, and a substantial fraction of surface of the metal cluster is unpassivated and available for catalytic reactions. G3-NAC1-Pt was used as catalyst in hydrogenation of o-nitroanisole. Under an H2 atmosphere, conversion of o-nitroanisole is above 99% after 3.5 h of reaction at 40 ℃ when n （Pt） ： n （G3-NAC1） in G3-NAC1-Pt is 30 and n （o-nitroanisole） ： n（G3-NAC1） is 900. The catalyst can be reused for several times without obvious loss of catalytic activity.