Study on in-situ lmmobilization of Size-Controlled Nanoparticles onto Solid Supports

在这项研究中，我们研究了一种新的方法来固定纳米粒子在油包水微乳液合成到固体载体。以金属醇盐为原料，采用微乳液法制备载体，并将纳米粒子原位固定在载体上，首先通过改变表面活性剂和有机溶剂的种类，将Rh/SiO_2的粒径控制在1.8 ~ 9.0 nm之间，然后将Rh/SiO_2纳米粒子原位固定在载体上。发现一些Rh颗粒部分或全部嵌入二氧化硅载体中，并且Rh颗粒表面不用于催化反应。然后，我们研究了暴露的金属表面与总金属表面的比率（=R比率）对纳米颗粒固定化的几个条件的依赖性。结果，通过缩短醇盐的水解时间和降低水解时的水含量，Rh颗粒的R比可以增加到约80%。Pd/ZrO_2中Pd粒子的R比也可以通过类似的方式增加。此外，为了提高R比，采用金属络合物纳米粒子而不是金属纳米粒子作为载体是可行的，用本方法制备的金属催化剂在CO加氢反应中表现出比传统浸渍法高得多的活性。此外，使用我们的方法制备的催化剂，每个活性中心的反应速率上的R比的效果进行了阐述。

In this study, we have studied a novel method for immobilization of nanoparticles synthesized in water-in-oil microemulsion onto solid supports. The support were prepared from metal alkoxide in microemulsion, and simultaneously the nanoparticles were in-situ immobilized on the support.First, Rh particle size of Rh/SiO_2 could be controlled in the range between 1.8 and 9.0 nm by changing the types of surfactant and organic solvent used in our method.Next, it was found that some of the Rh particles were partly or wholely embedded in silica supports and that the Rh particle surface were not used in catalytic reaction. Then, we investigated the dependence of the ratio of exposed metal surface to total metal surface (=R ratio) upon several conditions for nanoparticle immobilization. As a result, the R ratio of Rh particles could be increased to be about 80% by shortening the hydrolysis time of alkoxide and decreasing a water content at the hydrolysis. The R ratio of Pd particles in Pd/ZrO_2 also could be increased by a similar manner. Furthermore, in order to increase the R ratio, it was prefarable to immobilize metal complex nanoparticles rather than metal nanoparticles.The metal catalyst immobilized on supports by our method exhibited much higher activity than conventional impregnation catalysts in the hydrogenation of carbon monoxide. In addition, the effect of the R ratio on the reaction rate per an active site were elucidated using the catalysts prepared by our method.