基于"界面效应"设计高效乙炔氢氯化Au基催化剂

Due to the serious environmental pollution caused by usage of mercury catalyst, exploitation of effective non-mercury catalyst for acetylene hydrochlorination reaction is of great importance for the production of poly vinyl chloride (PVC) by acetylene method. In the previous investigation, Au catalyst exhibited excellent catalytic activity to acetylene hydrochlorination reaction, however, Au3+ active species was easily to be reduced to metallic Au0 under reaction condition, which was the predominant reason for the deactivation of Au catalyst. It is very important to enhance the stability of Au3+ species for the industrial application of Au catalyst in acetylene hydrochlorination reaction. Based on the "interface effect" between the Au nano-particles and MOx metal oxide (M represented transition metal), this project proposes a novel catalyst designing idea that stability of the catalyst can be promoted by controlling the Au3+ species on the interface. We will investigate the catalyst preparing method to optimalize the interface, and elucidate influence of the Au3+ content and Au-M bonding strenth on the catalytic performance of acetylene hydrochlorination reaction, and then discuss the adsorbing active site, adsorbing strenth and adsorbing order of the reactant molecular on the interface of the catalyst. Based on these scientific principle, this project try to adjust the structure of Au-MOx/C catalyst. The aim of this project is designing and preparing "non-mercury" catalyst with high catalytic performance for acetylene hydrochlorination reaction, and optimalize the operating reaction condition and regeneration technology to provoide scientific basis for the industrial application of non-mercury catalyst in the PVC route.

由于汞催化剂的使用导致严重的环境污染，高效乙炔氢氯化反应"非汞"催化剂的开发，对乙炔法生产聚氯乙烯(PVC)工艺具有重要意义。前期研究发现Au基催化剂具有较高的活性，但Au3+活性物种极易被还原为金属态的Au0，导致催化剂快速失活，提高Au3+的稳定性是乙炔氢氯化Au基催化剂工业应用的关键。本项目基于Au纳米颗粒与金属氧化物MOx之间的"界面效应"，提出调控界面上Au3+物种以提高催化剂稳定性的设计思路。考察获得界面最大化的催化剂制备方法；揭示界面上Au3+含量、Au-M键强度对乙炔氢氯化催化性能的影响规律；探讨反应物分子在界面上的吸附活性位、吸附强度和吸附次序；在上述科学规律的基础上对Au-MOx/C催化剂界面的微观结构进行精细调变，设计、制备高效的乙炔氢氯化反应"非汞"催化剂，并优化反应操作条件和再生工艺，为乙炔法生产PVC工艺中"非汞"催化剂工业应用提供科学依据。

乙炔氢氯化反应是电石乙炔法生产聚氯乙烯（PVC）工艺中的重要一环，Au催化剂对乙炔氢氯化反应具有很高的活性和选择性，但Au催化剂快速失活，提高Au催化剂的稳定性是乙炔氢氯化反应金催化剂工业应用的关键。本项目提出了基于“界面效应”设计高性能乙炔氢氯化Au催化剂的设计思路，揭示了Au催化剂与金属氧化物和配体之间的界面对Au3+活性物种的影响规律，提出了利用界面精细调变催化剂稳定性的解决方案，并优化了催化反应条件，为乙炔法生产PVC工业中非汞催化剂的工业应用提供了科学依据。主要的研究成果包括以下几方面：.1. 针对Au催化剂失活机理不明确的问题，将AuCl3催化剂进行了快速老化试验，发现在乙炔氢氯化过程中，除了Au3+还原为Au0之外，Au纳米颗粒的团聚是催化剂失活的另外一个原因（Scientific Reports, 2015, 5, 10533）.2. 添加金属氧化物TiO2为助催化剂，通过金属氧化物与Au的界面作用增强了HCl在催化剂表面的吸附强度，抑制了Au3+活性物种向金属态Au0的还原和Au纳米粒子的团聚，优化了实验条件；（ Chemical Engineering Journal, 2014, 242, 69-75）。.3. 通过添加含氮配体（邻菲罗啉）和含硫配体（硫脲）为助催化剂，阐明了配体与Au活性组分之间的界面效应，获得了有效提高Au催化剂在乙炔氢氯化反应中稳定性的方法，催化剂在快速老化试验条件下寿命超过40 h。（Catalysis Communications, 2014, 54(5), 61-65；Catalysis Science & Technology, 2016, 2016,6, 4254–4259）.4. 从碳载体孔结构调变的角度出发，通过调变模板剂将活性炭载体的孔径控制在2-50 nm的范围之内。负载AuCl3之后，发现催化剂的稳定性随孔径的增大呈现明显的增加规律，说明大孔径的碳载体可有效抑制催化剂的积碳失活（Catalysis Science & Technology, 2015, 5, 1035-1040）；.5. 考虑到多相催化剂载体与活性组分的界面作用，进一步从载体改性角度出发开展了提高Au催化剂寿命的工作。对碳载体表面掺杂氮原子后，氮原子中孤对电子向Au原子转移，提高了Au催化剂的寿命。