苯部分加氢新型钌基核壳催化剂的创制及性能研究

The core-shell structured nanocatalysts have been widely studied owing to the advantages in utilizing noble metals and improving catalytic performances, while the catalyst with a Ru shell is rarely studied, which limits its application. The present proposal intends to fabricate the supported M@Ru (M = Fe, Co, Ni, or Cu) core-shell nanocatalysts consisting of a M core and a Ru shell by galvanic replacement, using the previously supported Fe, Co, Ni, or Cu nanoparticles as sacrificial templates. The morphology, size, composition, and shell thickness of the metallic nanoparticles on the catalysts will be controlled by means of thermodynamic manipulation, kinetic manipulation, and chemical etching. Meanwhile, the characters of supports such as hydrophilicity, pore size, crystallographic form, and composition will also be tuned. Afterwards, we will characterize the structural and electronic characteristics of the catalysts, and investigate the influences of the morphology, size, composition, shell thickness, and support of these novel catalysts on the catalytic performances in partial hydrogenation of benzene to cyclohexene. It is expected that this project will enable us to: 1) reveal the superiorities of galvanic replacement in adjusting the catalyst structure and improving the catalytic performance as compared to the conventional preparation methods, 2) illuminate the relationships between the morphology, size, composition, and shell thickness of the catalysts and the catalytic performances in partial hydrogenation of benzene, 3) identify the effect of support, the stability, and the regeneration ability of the catalyst, 4) obtain the innovatively high-performed and stable catalyst for partial hydrogenation of benzene, and 5) promote the technological advance for the efficient transformation and utilization of benzene.

核壳结构纳米催化剂具有贵金属利用率高、催化性能好等优点而被广泛研究，但以钌为壳层的催化剂研究较少，使其应用受到限制。本项目拟采用先将铁、钴、镍或铜等纳米粒子负载到载体上，然后以其为模板置换钌离子的设计思想，制备内核为模板粒子、壳层为钌的负载型核壳纳米催化剂。从热力学、动力学和化学腐蚀三方面调控催化剂上金属纳米粒子的形貌、粒径、组成及壳层厚度等，同时对载体的亲水性、孔径、晶型和组成进行调控，对催化剂的结构特征和电子特征进行表征，考察该新型催化剂的形貌、粒径、组成、壳层厚度和载体性质对其苯部分加氢制环己烯性能的影响。项目预期将揭示置换法与传统方法相比在调控催化剂的结构以及提高其催化性能等方面存在的优势，阐明催化剂的形貌、粒径、组成及壳层厚度与苯部分加氢性能之间的关系，探明催化剂的载体效应、稳定性和再生性，为苯部分加氢提供高效、稳定的原创催化剂体系，推动苯资源高效转化利用的技术进步。

苯选择加氢制备环己烯在获得高值化学品的同时，兼具原子经济、原料丰富、操作简便等优点，因而受到广泛关注。然而，该反应热力学决定了中间产物环己烯很容易深度加氢成环己烷，从而限制了高产物选择性的获得。如何从催化剂的结构设计出发，获得具有高活性、高选择性的催化剂，是该反应重点研究的方向之一。我们在国家自然科学基金委员会的资助下，在催化剂制备方法、助剂、载体微观结构三方面开展了富有创新性的研究工作。首先，基于活泼金属粉末与钌盐之间的置换反应制备了助剂含量可控的Ru-Zn/ZrO2催化剂，发现Zn可改变Ru与苯和环己烯之间的相互作用，从而提高环己烯选择性。进一步采用在载体表面预负载模板金属纳米粒子的方法，提高了金属-载体结合力和Ru的分散度。其次，对助剂种类进行了拓展，发现Pd、Pt等贵金属助剂与Ru在表面形成了合金，其有利于提高产物选择性。最后，对载体种类进行了拓展，制备了酸量可控的AlOOH-SiO2复合物，确定了Ru/AlOOH-SiO2催化剂上Lewis酸量与苯加氢本征活性和环己烯选择性之间的定量关系。同时，制备了一系列结构新颖的TiO2载体，包括暴露不同程度{100}面的锐钛矿TiO2纳米棒、不同形貌(纳米片、纳米棒、纳米花)板钛矿TiO2、不同锐钛矿/金红石摩尔比的TiO2、由暴露不同程度{001}面的锐钛矿TiO2纳米片自组装形成的多级结构纳米球、表面形貌不同的锐钛矿TiO2亚微球、暴露不同晶面({101}、{001}、{010})的锐钛矿等，阐明了载体形貌、晶面、配位不饱和位点、组成、孔径等对Ru/TiO2催化剂苯加氢活性和环己烯选择性的影响及作用机理，发现其主要通过改变苯加氢和环己烯加氢的相对速率、阻塞环己烯在催化剂表面的吸附位点、降低环己烯的吸附量等提高环己烯选择性。上述研究成果为理性设计高效苯选择加氢催化剂、促进催化剂的工业应用提供了依据，对高值化学品的高效生产具有重要意义。项目实施期间，已发表SCI收录论文9篇，CSCD收录论文1篇，其中7篇影响因子大于5。提交会议论文1篇，培养硕士1名。