The significance of the oxidation state of gold in heterogeneous catalysis

金的氧化态在多相催化中的意义

• 批准号: EP/I038748/1
• 负责人: Philip Davies
• 金额: $ 59.07万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FI038748%2F1
• 关键词: significance; oxidation; state; gold; heterogeneous

We aim to construct a detailed picture of the processes, intermediates and active sites involved in the hydrochlorination of ethyne over gold chloride nanoparticles supported on carbon surfaces. The hydrochlorination of ethyne provides an alternative route to vinyl chloride which at present is manufactured by a two step process involving the oxychlorination of ethene to form 1,2-dichloroethane followed by cracking. Vinyl chloride is polymerised to polyvinyl chloride (PVC) an important polymer with widespread applications in the construction and electronics industries. Sixty years ago vinyl chloride was almost exclusively made by the direct hydrochlorination of ethyne, which derives from coal, over a mercury chloride catalyst but the availability of inexpensive ethene from oil led to a change of manufacturing route despite the lower yields, lower product purity and higher costs for waste treatment. Now, dwindling oil reserves and increasing environmental awareness is dictating a search for to the alternatives to the oxychlorination route. The safety and environmental issues posed by HgCl2 prevent a return to the former catalyst but Hutchings and co-workers have proven that gold supported on carbon can be a viable alternative. Our project will inform the development of such catalysts but will also provide an important new window on gold catalysis.Whilst catalysis by gold nanoparticles is an established phenomenon particularly in relation to selective oxidation processes, the key points of the active site and the reaction mechanism remain very controversial despite extensive work. Different researchers have separately emphasised the importance of different aspects of gold catalysts for example: the size of the gold particles; the interface between the gold and the support and the oxidation state of the gold. Fierro-Gonzalez & Gates ascribe this controversy to the fact that attention has largely focussed on mechanistic studies of CO oxidation and suggest that this experimentally appealing reaction is not as straight forward as it appears. They recommend that more diverse systems be investigated at a fundamental level if further progress is to be made in understanding the nature of the active site in gold catalysis and thus provide direction to the development of better gold catalysts. Au/C catalysts have received remarkably little attention from the surface science community (in contrast to the gold/oxide catalysts) and a study of the fundamental chemistry underlying this system therefore offers the prospect not only of advancing the development of an important future catalyst but also of shedding new light on some of the fundamental principles of gold catalysis. A powerful combination of surface spectroscopy, surface microscopy and surface kinetic methods applied in conjunction with computational chemistry will be focussed on identifying and characterising the active states of gold in ideal models of the hydrochlorination catalyst. However, in practice, the Au/C hydrochlorination catalyst consists of a high area activated carbon exhibiting a variety of functional groups at the surface which may influence the deposition and stability of the adsorbed gold halides. To address this issue the project involves three separate parallel strands with studies of gold deposited from aqueous solutions on modified HOPG and activated carbon under ambient conditions providing the bridge between model surface science/computational studies of gold halides on HOPG and the practical catalysis.

我们的目标是构建碳表面负载的氯化金纳米粒子上乙炔氢氯化所涉及的过程、中间体和活性位点的详细图片。乙炔氢氯化提供了氯乙烯的替代途径，目前氯乙烯通过两步工艺生产，涉及乙烯氧氯化形成1,2-二氯乙烷，然后裂解。氯乙烯聚合成聚氯乙烯 (PVC)，这是一种重要的聚合物，广泛应用于建筑和电子行业。六十年前，氯乙烯几乎完全是通过在氯化汞催化剂上直接氢氯化乙炔来制造的，而乙炔是从煤中提取的，但从石油中获得廉价的乙烯导致了生产路线的改变，尽管产量较低，产品纯度较低，废物处理成本较高。现在，石油储量的减少和环境意识的提高要求人们寻找氧氯化路线的替代方案。 HgCl2 带来的安全和环境问题阻止了回到以前的催化剂，但哈钦斯和他的同事已经证明，碳载金可以是一种可行的替代品。我们的项目将为此类催化剂的开发提供信息，同时也将为金催化提供一个重要的新窗口。虽然金纳米粒子催化是一种既定现象，特别是与选择性氧化过程相关，但活性位点和反应机制的关键点仍然存在尽管工作量很大，但仍颇受争议。不同的研究人员分别强调了金催化剂不同方面的重要性，例如：金颗粒的大小；金和载体之间的界面以及金的氧化态。 Fierro-Gonzalez 和 Gates 将这一争议归因于这样一个事实：注意力主要集中在 CO 氧化的机理研究上，并表明这种在实验上有吸引力的反应并不像看起来那么简单。他们建议，如果要在了解金催化活性位点的性质方面取得进一步进展，就应该在基础层面上研究更多样化的系统，从而为开发更好的金催化剂提供方向。 Au/C 催化剂很少受到表面科学界的关注（与金/氧化物催化剂相比），因此对该系统基础化学的研究不仅为推进未来重要催化剂的开发提供了前景，而且还为金催化的一些基本原理提供了新的启示。表面光谱、表面显微镜和表面动力学方法与计算化学的强大结合将集中于识别和表征氢氯化催化剂理想模型中金的活性状态。然而，在实践中，Au/C氢氯化催化剂由高面积活性炭组成，表面具有多种官能团，这可能会影响吸附的卤化金的沉积和稳定性。为了解决这个问题，该项目涉及三个独立的平行链，研究在环境条件下从水溶液中沉积在改性 HOPG 和活性炭上的金，从而在 HOPG 上卤化金的模型表面科学/计算研究与实际催化之间架起桥梁。

项目成果

XPS and STM studies of the oxidation of hydrogen chloride at Cu(100) surfaces

• DOI: 10.1016/j.susc.2015.12.024
• 发表时间: 2016-08
• 期刊: Surface Science
• 影响因子: 1.9
• 作者: H. Altass;A. Carley;P. R. Davies;R. Davies

Investigating the Effects of Surface Adsorbates on Gold and Palladium Deposition on Carbon

• DOI: 10.1007/s11244-021-01423-2
• 发表时间: 2021-03
• 期刊: Topics in Catalysis
• 影响因子: 3.6
• 作者: B. Bowden;Josh A. Davies-Jones;M. Davies;P. R. Davies;D. Morgan;Mala A. Sainna;D. Willock

Al-doped Fe2O3 as a support for molybdenum oxide methanol oxidation catalysts.

• DOI: 10.1039/d0cp01192d
• 发表时间: 2020-05
• 期刊: Physical chemistry chemical physics : PCCP
• 作者: M. Bowker;Pip Hellier;Donato Decarolis;D. Gianolio;K. Mohammed;A. Stenner;T. Huthwelker;P. Wells

Solvent Free Synthesis of PdZn/TiO2 Catalysts for the Hydrogenation of CO2 to Methanol

• DOI: 10.1007/s11244-018-0885-6
• 发表时间: 2018-04-01
• 期刊: TOPICS IN CATALYSIS
• 影响因子: 3.6
• 作者: Bahruji, Hasliza;Esquius, Jonathan Ruiz;Jones, Wilm
• 通讯作者: Jones, Wilm

Pd/ZnO catalysts for direct CO2 hydrogenation to methanol

• DOI: 10.1016/j.jcat.2016.03.017
• 发表时间: 2016-11-01
• 期刊: JOURNAL OF CATALYSIS
• 影响因子: 7.3
• 作者: Bahruji, Hasliza;Bowker, Michael;Lalev, Georgi
• 通讯作者: Lalev, Georgi