负载型铑基单原子催化剂的创制及其在氢甲酰化反应中的应用

Hydroformylation, producing high value-added aldehydes from alkenes and syngas, is one of the most important homogeneously catalyzed industrial processes. At present, the phosphine-ligands containing Rh complexes dominate the industrial hydroformylation catalysts because of their superior reactivity and selectivity. The major issue, however, lies in the difficulty of separating homogenous catalyst from products, and the reusability of the catalyst. We propose to design and develop single-atom Rh catalysts for the hydroformylation process. Single-atom catalysts have the advantages of both homogeneous catalysts such as “isolated sites” and heterogeneous catalysts such as stability, reusability, thus would be potential alternative to the traditional homogeneous catalyst. The utilization of single-atom catalysts might provide an efficient green avenue for the synthesis of fine chemicals of aldehydes. The key scientific issues of this proposal are the manipulation of the reactivity and selectivity by rational design and tuning the catalysts’ components, and thorough catalytic mechanism investigation. The proposal contains the following aspects: first, the rational design and preparation of suitable Rh based single-atom catalysts; second, the characterization and catalytic performance test of the synthesized catalysts to study their structure-performance relationships; third, the in-depth study of the catalytic mechanism. The application of this proposal is significant to the development of new types of highly efficient heterogeneous catalysts and the understanding of their catalytic nature. It may also provide reference to the heterogenization of homogenous process in chemical industry.

利用氢甲酰化反应以合成气和烯烃为原料制备醛类化合物，是合成气高附加值转化的有效手段。目前工业生产中采用的均相铑配合物催化剂，具有难以替代的高活性和高选择性，但不易与产物分离，难以循环使用。本申请提出设计、制备负载型单原子铑基催化剂，利用单原子催化剂兼具均相催化剂“孤立活性位点”与多相催化剂稳定、易分离、可重复使用的特点，为醛类精细化学品的合成提供绿色高效的新途径。相关过程要解决的关键科学问题在于通过设计催化剂来调控化学反应的活性与选择性以及加深对单原子催化本质的认识。主要研究内容包括催化剂的设计与制备，催化剂组成、结构与性能之间构效关系的建立以及催化机理的深入探索。项目实施对于进一步开发新型高效多相催化剂并理解其活性中心本质具有重要的科学意义，在工业生产上可能为均相过程多相化起到借鉴作用。

本项目制备出Rh基单原子催化剂，在氢甲酰化反应中表现出与均相催化剂相当的优异活性。首次从实验上证明单原子催化剂兼具均相催化剂的高活性和多相催化剂的稳定性，有望成为均相反应多相化的新途径。该催化剂优异的高温（800 oC）抗烧结性能，提示我们单原子催化剂的稳定性来源于金属-载体强相互作用。铂族元素在工业催化中是重要的活性物种，所以本项目进一步研究了铂单原子在氧化物载体上的稳定机制。用共沉淀法和纳米粒子高温挥发法都能得到高载量的Pt/Fe2O3单原子催化剂，即使在高温下焙烧也不团聚。理论计算和对照实验共同说明Pt在氧化物载体上能够稳定分散的根本原因是Pt与还原性载体之间形成氧桥联的共价键，与载体表面缺陷数量无关。本项目对于单原子催化剂的创制和稳定机制的探讨将为有针对性地调控金属（活性中心）-氧化物（载体）组合，设计开发高活性、高载量、耐高温的铂族金属单原子催化剂提供指导。