负载型Pt-Au双金属催化材料的理性设计、化学制备及其加氢异构性能

Hydroisomerization is an important catalytic process in the petroleum industry. Controlled preparation of bifunctional catalysts of metal active site is one of the perspective topics in catalysis science and technology. Pt-Au bimetallic catalysts are widely used to catalyze different types of reactions. However, up to now, there is little study for using Pt-Au catalysts in hydroisomerization of n-alkane. The project proposed here is based on our recent results for hexadecane hydroisomerization over Pt/ZSM-48 and Au/ZSM-5 catalysts for catalytic cracking of light diesel oil at lower temperatures. This proposal plans to design rationally the Pt-Au bimetallic catalysts according to the electronic structure theory. To understand formation mechanism and structural changes of the Pt-Au bimetallic catalysts, a number of in situ charaterization techniques will be performed. Thereby, the structures and the compositions of the Pt-Au bimetallic catalysts can be tuned. Hydroisomerization of hexadecane over the Pt-Au bimetallic catalysts will be investigated in order to well understand the relationship among their structure, composition, and properties. The structure-reactivity relationship and reaction mechanism of Pt-Au bimetallic catalysts improving the yield of iso-alkane are explored and clarified. The implementation of the project will lay the scientific basis on the controllable synthesis of Pt-Au bimetallic catalysts and their applications in catalytic hydroisomerization field at "molecular engineering" level. The related conclusions will be explanded into not only develop novel hydroisomerization catalyst with high activity and high iso-alkane selectivity, but also design and controlled preparation of the other bimetallic catalysts.

加氢异构反应在当今的石油工业中发挥着重要的作用，而其所用双功能催化剂金属活性位的调控仍是催化科学领域前瞻性的课题之一。Pt-Au双金属催化剂的研究已相当活跃，而在长链烷烃加氢异构反应体系中的研究尚无人问津。本项目拟在前期Pt/ZSM-48催化剂对十六烷加氢异构和Au/ZSM-5低温催化裂解柴油反应研究的基础上，运用电子结构理论，理性设计Pt-Au双金属催化新材料；采用多种原位表征技术弄清Pt-Au双金属催化剂的形成机理和结构变化规律，实现Pt-Au双金属催化剂的结构和组成的可控调变；以典型的十六烷加氢异构为探针反应，揭示催化剂的结构和组成与加氢异构反应性能的内在规律性联系；探索和阐明Pt-Au双金属催化剂提高异构烷烃收率的构效关系和反应机理，为实现从分子层面对Pt-Au双金属催化材料进行结构设计与性能调控，为开发高活性、高异构烷烃选择性的加氢异构催化剂和研制其它双金属催化剂提供理论基础。

加氢异构反应需要金属位与酸性位协同作用的双功能催化剂，本项目通过调变Pt-Au双金属活性中心来设计高效的加氢异构催化剂，以提高异构烷烃的收率。在将Pt-Au双金属应用于加氢异构反应之前，我们需要确定Au是否具有加氢/脱氢活性，Au在高温反应下是否稳定？首先通过简单快速的方法合成出Au@ZIF-8催化剂，将其用于硝基化合物的选择加氢反应中，研究Au催化剂的加氢活性。通过对不同Au担载量，不同Au粒径和不同反应物类型的硝基化合物的研究，可以发现Au催化剂具有优异的加氢活性。其次通过制备Au/ZSM-5双功能催化剂，将其用于正辛烷裂解制丙烯的反应中，研究Au催化剂的脱氢活性。通过研究不同Au粒径和化学状态，证明了Au催化剂具有优异的脱氢活性。同时引入第二种元素La，可以有效提高Au/ZSM-5在高温下催化裂解正辛烷制丙烯的稳定性。基于以上对Au催化剂的加氢/脱氢和稳定性的研究，通过制备Pt-Au双金属催化剂，将Pt-Au双金属催化剂应用于十六烷加氢异构反应。通过精细调变金属催化活性，克服单一金属催化剂的缺点，进而调整载体酸中心与金属活性中心之间的协同催化作用，提高异构十六烷的收率。除此之外，还研究了酸性载体ZSM-48对加氢异构性能的影响，揭示了介孔的形成有利于产物的扩散，提高了异构烷烃的收率，为Pt-Au双金属催化剂寻找更加与之匹配的酸性载体提供了理论基础。