Fundamental Sulphur-Chemistry of Molybdenum Carbide Surfaces: Towards Catalytic Exploitation of Transition Metal Carbides

碳化钼表面的基本硫化学：过渡金属碳化物的催化开发

• 批准号: EP/J015261/1
• 负责人: Stephen Jenkins
• 金额: $ 72.46万
• 依托单位: University of Cambridge
• 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%2FJ015261%2F1
• 关键词: Fundamental; Sulphur; Chemistry; Molybdenum; Carbide

Many of the most important chemical reactions underlying the modern world are made possible only by the use of catalysts. These are substances that either speed up a chemical reaction or improve its selectivity towards the desired product - preferably both - whilst not themselves being used up in the process. Classic examples include ammonia synthesis from nitrogen and hydrogen, using an iron catalyst, and the manufacture of synthetic petrol or diesel from carbon monoxide and hydrogen, using a cobalt catalyst. Both of these processes are crucial to future economic development (ammonia for fertiliser production, and synthetic fuels for carbon-neutral transportation) and it is indeed fortunate that the metals involved as catalysts are in plentiful supply.More often, the catalysts in use today are based on expensive and rare precious metals, such as platinum, palladium or rhodium (all used, for example, in the catalytic converters that remove harmful gases from car exhausts prior to emission) and the search for cheaper or better alternatives is correspondingly urgent. Another perennial issue, besides the cost and scarcity of certain catalysts, is one of gradual deactivation by the build-up of contaminants at the surface of the catalyst. Although the catalyst itself is not used up, the microscopic active sites where the chemical reactions actually occur can become blocked by unreactive atoms, and removing these to reverse the 'poisoning' of the catalyst can often involve considerable effort or expense. Again, the search for unconventional catalysts that are less prone to poisoning is extremely pressing.In the present project, we will study the fundamental surface chemistry of a particularly unconventional catalyst, molybdenum carbide, which is extremely promising as a cheaper alternative to platinum and similar precious metals in many types of catalysis. One of the most interesting aspects of this chemistry relates to the behaviour of sulphur, which is a notorious catalyst poison that is deposited upon the decomposition of sulphur-containing molecules. Molybdenum carbide is known to be particularly resistant to sulphur poisoning, and indeed can be used to remove sulphur from the mixture of molecules produced by oil refineries (processing either traditional fossil fuels or green carbon-neutral biofuels) by enhancing the reaction of sulphur compounds with hydrogen in a process known as hydrodesulphurisation. Not only can this be of importance in reducing automotive and power-plant sulphur emissions (responsible for acid rain) but it can also massively improve the suitability of refinery products for use as feedstocks in the production of commodity chemicals, where the presence of sulphur compounds would poison many of the common catalysts. At present, this important function of hydrodesulphurisation is carried out with a catalyst containing cobalt and molybdenum sulphide, but molybdenum carbide could represent a leap forward in industrial practice from both the economic and the environmental perspectives.In order to understand the interaction of sulphur compounds with molybdenum carbide, we will carry out infra-red spectroscopic measurements, capable of identifying the various products of decomposition that end up bound to the surface, and supersonic molecular beam measurements that allow us to determine reaction rates as a function of surface conditions and the state of incoming molecules. We will work under ultra-high vacuum conditions, and with extremely well-characterised samples, so as to obtain the most detailed results possible with state-of-the-art techniques. The information we can gather in this way will be of use to other scientists, in both academia and industry, who seek to optimise working catalysts based on this material.

现代世界的许多最重要的化学反应只有使用催化剂才能实现。这些物质要么加快化学反应，要么提高其对所需产品的选择性 - 最好是两者 - 而本身并不在此过程中使用。经典的例子包括使用铁催化剂与氮和氢合成的氨合成，以及使用钴催化剂的碳一氧化碳和氢的合成汽油或柴油制造。 Both of these processes are crucial to future economic development (ammonia for fertiliser production, and synthetic fuels for carbon-neutral transportation) and it is indeed fortunate that the metals involved as catalysts are in plentiful supply.More often, the catalysts in use today are based on expensive and rare precious metals, such as platinum, palladium or rhodium (all used, for example, in the catalytic converters that remove harmful在排放之前，汽车排气中的气体和更便宜或更好的替代方案非常紧急。除了某些催化剂的成本和稀缺性外，另一个多年生的问题是通过在催化剂表面污染物逐渐停用的逐渐停用的问题。尽管催化剂本身没有用完，但化学反应实际发生的微观活性位点可能会被无反应性原子阻塞，并去除这些反应以扭转催化剂的“中毒”通常会涉及相当大的努力或费用。同样，寻找较不易中毒的非常规催化剂的搜索非常紧迫。在本项目中，我们将研究一种特别非常规催化剂，甲只是甲虫的基本表面化学反应，在许多类型的催化催化中，这是对Platinum较便宜的贵金属和类似贵金属的替代品，这是非常有希望的。该化学的最有趣的方面之一与硫的行为有关，硫是一种臭名昭著的催化剂毒药，沉积在含硫硫的分子的分解上。已知甲状腺素对硫中毒特别具有抵抗力，实际上可以用来从油中炼油厂产生的分子（处理传统化石燃料或绿色碳中性生物燃料）中的分子中去除硫，通过增强氢与氢与氢在已知的Asyrodesulodesulodesulodesulodesulodeatration ardyrodeation中的反应来增强硫的反应。这不仅在减少汽车和动力植物的硫排放量（负责酸雨）方面也很重要，而且还可以大大提高炼油厂产品的适合性，以用作商品化学物质的原料，在这种化学物质的生产中，硫化合物的存在会毒害许多常见催化剂。目前，通过含有钴和硫化钼的催化剂来实现氢化化的这种重要功能，但是碳化物的钼可以代表工业实践中的飞跃，从经济和环境的角度来看。为了了解能力衡量的量子量的各种量子，我们将携带量子的相互作用。最终结合到表面的分解以及超音速分子束测量值，使我们能够确定反应速率与表面条件的函数和传入分子的状态。我们将在超高的真空条件下工作，并使用特征良好的样品，以便通过最先进的技术获得最详细的结果。我们可以以这种方式收集的信息将对学术界和行业中的其他科学家有用，他们试图根据该材料优化工作催化剂。