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

本文研究了酯类模型化合物γ-丁内酯在负载型Pt-Sn双金属催化剂上的加氢反应。Sn/Pt比的影响也进行了研究。Sn/Pt比值小于1的Pt-Sn/SiO_2催化剂对γ-丁内酯的加氢活性较低。当Sn/Pt比在1 ~ 2之间时，Sn的加入使催化剂的活性明显提高。催化剂的X-射线粉末衍射图谱表明，Pt金属和Pt-Sn合金的共存带来了活性的提高。当Sn/Pt比小于1时，催化剂中只有Pt晶体，而当Sn/Pt比大于2时，催化剂中只有PtSn合金相。Sn/Pt比在1 ~ 2范围内的催化剂具有较高的活性。并考察了Pt/SiO_2催化剂中其它助剂对γ-丁内酯加氢反应的影响。对Al、Ge、In、Pb、Ti等金属元素作为Pt/SiO_2的添加剂进行了实验研究。Al、Ge和In的加入表明没有观察到Pt在SiO_2上形成合金。Pb的加入使PtPb合金在SiO_2载体上形成。虽然Pb的加入对γ-丁内酯的加氢反应有促进作用，但对Pt-Pb/SiO_2催化剂的活性影响不大。Al、Ge、In和Pb的加入只会降低活性Pt的比表面积，而添加钛的Pt-Ti/SiO_2催化剂的活性有所提高。钛可以修饰Pt表面，选择性地活化γ-丁内酯中的羰基。Pt/TiO_2的SMSI是Ti元素对Pt表面的类似改性

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