配位离子液体稳定金离子价的调控力及其机制研究

How to stabilize the valence of the Au ionic catalysts under acetylene hydrochlorination conditions has been a unsolving scientific problem and thus has drawn extensive attentions. Meanwhile, it limits the industrial application of Au-based catalysts in the hydrochlorination of acetylene. In this project, we focus on studying the mechanism and regulating methods of the valence change of oxidation state Au ion in the hydrochlorination of acetylene. Due to the coordination effect, electronic effect and the oxidizing capability of coordinated ionic liquids, this project aims to use supported coordinated ionic liquids to construct a microenvironment in which active Au cations species can be dispersed and their chemical valence states can be maintained in the hydrochlorination of acetylene. The design and synthesis methods of coordinated ionic liquids were explored. The Aux+ content in coordinated ionic liquid, the Au-X bond nature of formed complexes and the electron transfer between Au center and Mx+ on the catalytic activity, selectivity and stability of the supported ionic liquid-Au catalysts were revealed. The mechanism of stabilizing ionic Au species by coordinated ionic liquids, and the catalysis and deactivation mechanism of the coordinated ionic liquid-Au catalytic system in the hydrochlorination of acetylene were elucidated. Based on the above scientific outcomes, modification of the structure and composition of the coordinated ionic liquid-Au catalytic system is further performed in order to obtain high efficient Au-based catalyst for acetylene hydrochlorination. This project will lay a foundation for the industrial application of the environmentally-friendly Au-based catalysts for acetylene hydrochlorination.

在乙炔氢氯化反应条件下如何保持金离子催化剂的化学价态稳定一直是受到广泛关注的科学问题，同时也影响金基催化剂在工业上的实际应用。本项目聚焦研究乙炔氢氯化反应中金离子的价变机理及调控方法。利用配位离子液体的“配位效应”、“电子效应”以及其金属阳离子Mx+的氧化性能，本项目提出采用负载配位离子液体来分散金离子活性相以及构建氯乙烯合成条件下催化剂自身维持Aux+（x=1或3）氧化态微环境的设计思路。探索配位离子液体的设计和合成方法；揭示负载配位离子液体中Aux+含量、配合物中Au-X键性质、Au中心与Mx+之间电子传递等因素对乙炔氢氯化催化性能的影响规律；阐明配位离子液体稳定Aux+的机制和配位离子液体-金催化剂在乙炔氢氯化反应中的催化、失活机理；在上述科学规律的基础上对催化体系的结构和组成进行调变，构建高效的乙炔氢氯化反应金基催化剂，为乙炔法工艺中环保型金基催化剂的工业应用奠定基础。

在本项目的资助下，我们主要进行了四个方面的研究工作。第一，我们研究发现配位离子液体对于乙炔氢氯化制备氯乙烯具有较高的催化稳定性。配位离子液体稳定的阳离子金具有可控的尺寸分布以及超长的催化寿命（>300 h），同时没有伴随明显的活性降低和金属态的金生成。研究结果显示该催化反应属于结构敏感反应，当阳离子金以[AuCl4-]配位结构存在时的催化稳定性最高（Catal. Sci. Technol., 2016, 6, 3263-3270）；第二，我们构建了Au-Cu原位自氧化机制用于乙炔氢氯化，并结合配位离子液体的存在有目的性的降低Au3+标准电极电势，提高自氧化效率。得益于Au-Cu原位自氧化机制，该催化剂表现出极高的催化效率168.5 h-1（Appl. Catal. B: Environ.2017, 206, 56-64.）；第三，针对乙炔气氛下Pd的升华流失现象，利用Pd与离子液体的配位效应以及载体的微孔限域效应，抑制Pd的升华流失（Chem. Eng. J. 2019, 360, 38-46）。该合成策略在乙炔氢氯化反应中表现出极高的催化稳定性。接着，我们研究了配位离子液体对Pd原子的d带电子分布影响，建立了转移电子效应对乙炔的活化机制，为调控催化剂的性能提供了一条新的途径（Catalysts 2020, 10, 24-38）。最终，我们尝试了将配位离子液体技术应用于工业放大实验中。催化剂在工业条件下稳定运行了2000小时，保持乙炔转化率在99%以上，意味着配位离子液体技术在工业应用中的巨大潜力。