Design of Metallic Catalysts with Molecular Recognizing Function and Their Catalytic Activity for Highly Selective Challenging Reduction Reaction

研究了负载型Pt-Sn双金属催化剂上γ-丁内酯的加氢反应。研究了锡铂比的影响。Sn/SiO_2的Sn/Pt比小于1，对γ-丁内酯的加氢活性较低。Sn/Pt比值在1 ~ 2之间时，Sn对Pt/SiO_2的活性有明显的增强作用。催化剂的x射线衍射粉末谱图表明，Pt金属和Pt- sn合金的共存使活性增强。当Sn/Pt比小于1时，催化剂只显示Pt晶体，而当Sn/Pt比大于2时，催化剂只显示PtSn合金相。Sn/Pt比值在1 ~ 2之间的催化剂活性较高。在Pt/SiO_2催化剂中还研究了其他添加剂对γ-丁内酯加氢的影响。测试了铝、Ge、In、Pb和Ti作为Pt/SiO_2的添加剂。Al、Ge和In的加入表明SiO_2上未与Pt形成合金。Pb在SiO_2载体上形成PtPb合金。Pb的加入对γ-丁内酯的加氢反应有促进作用，但在Pt-Pb/SiO_2催化剂上只观察到活性的降低。添加Al、Ge、In和Pb只会降低活性Pt的表面积，而添加钛的Pt催化剂Pt- ti /SiO_2活性增强。钛可以修饰Pt表面，选择性激活γ-丁内酯中的羰基。Ti元素对Pt表面的类似修饰被称为Pt/TiO_2的SMSI

Hydrogenation of γ-butyrolactone as a model compound of esters has been studied over supported Pt-Sn bimetallic catalysts. Effect of Sn/Pt ratio was also investigated. The Pt-Sn/SiO_2, which Sn/Pt ratio was less than unity, indicated a low activity for the hydrogenation of γ-butyrolactone. The Sn/Pt ratio between 1 and 2 showed the marked enhancement of the activity by the addition of Sn to Pt/SiO_2. X-ray diffraction powder patterns of the catalysts suggested that co-existence of Pt metal and an alloy of Pt-Sn brought about the enhancement of the activity. The catalysts, which Sn/Pt ratio was less than unity, indicated only Pt crystals, whereas the catalysts which Sn/Pt ratio was higher than 2, showed only PtSn alloy phase. The higher activity was observed on the catalysts of which Sn/Pt ratio was in the range between 1 and 2. Other additives in the Pt/SiO_2 catalysts were also investigated for the hydrogenation of γ-butyrolactone. Aluminium, Ge, In, Pb and Ti were tested for the additives of Pt/SiO_2. The addition of Al, Ge, and In indicated no alloy formation with Pt on SiO_2 was observed. The addition of Pb brought about the formation of PtPb alloy on the SiO_2 support. Although Pb addition was expected to enhance the hydrogenation reaction of γ-butyrolactone, only decrease of activity was observed on Pt-Pb/SiO_2 catalysts. The addition of Al, Ge, In and Pb would only decrease the surface area of active Pt The titanium-added Pt catalysts, Pt-Ti/SiO_2 indicated enhancement of the activity. Titanium would modified the Pt surfaces and selectively activate carbonyl, group in γ-butyrolactone. The similar modification of Pt surfaces by Ti element was well known as SMSI of Pt/TiO_2