Bio-inspired catalysts for the activation of aliphatic C-H bonds: toward the development of novel green processes

用于活化脂肪族C-H键的仿生催化剂：致力于开发新型绿色工艺

• 批准号: RGPIN-2014-06336
• 负责人: Castonguay, Annie
• 金额: $ 2.33万
• 依托单位: Institut national de la recherche scientifique
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=632664
• 关键词: Bio; inspired; catalysts; activation; aliphatic

Nature has long been a source of inspiration for both scientists and artists. Some of the most ingeniously designed products and gadgets familiar to millions of people worldwide owe their origin to seemingly simple forms and patterns found in plants and wildlife. Although we lately learned plenty of information about how nature proceeds to perform various efficient chemical transformations, biological systems are complicated and still far from being fully understood. An example of such complex systems is the mild way nature converts atmospheric nitrogen to ammonia. For 100 years, ammonia has been exclusively produced from nitrogen and hydrogen gas via the Haber-Bosch process, a technique that requires very harsh conditions (350-550 °C, 150-350 atm). In contrast, some enzymes found in nature known as nitrogenases are able to easily achieve this transformation at ambient temperature and pressure. As it is the case for the breakage of the strong nitrogen triple bond, the controlled activation and functionalization of strong C-H bonds in hydrocarbons also remains a challenge. The vast majority of precious raw materials like liquid and gaseous hydrocarbons are simply burnt as fuels for heating and transportation, and only a modest portion of these C-H bond containing molecules (alkanes and aromatics) are converted into chemical intermediates on a large-scale for use in the chemical industry. The transition metal-catalyzed dehydrogenation of alkanes, which produces olefins, the major feedstock of chemical industry, is a green approach to bond construction strategies. This reaction allows the substitution of highly reactive mutagenic halogenated starting reagents that are currently used by industry by simple C and H containing compounds, and prevents waste production. The dehydrogenation of alkanes also generates hydrogen gas, which is a coveted non polluting energy source. Importantly, due to the reversibility of the reaction, catalysts able to dehydrogenate alkanes can potentially find applications in the field of hydrogen storage. There is a need for greener catalysts to be developed. For example, one of the technologies currently used by industry and which accounts for over 90% of ethylene production in North America requires temperatures in excess of 800 °C and produces 1-3 tons of CO2/ton of ethylene. Transition metal complexes as homogeneous catalysts for the dehydrogenation of alkanes allow milder reaction conditions as well as selectivity, but are mostly based on precious metals such as Ir and Rh. Using nature as a source of inspiration, our group will study complexes based on inexpensive metals, which have traditionally been overlooked to achieve the dehydrogenation of alkyl chains, and that are responsible for the activity of many enzymes, such as iron (Fe) or tungsten (W). Research on alternatives to the use of noble metals is a novel approach in the field of C-H activation catalyst development. Avoiding precious metals will lead to cheaper catalysts with minimum environmental and toxicological impact, and which can accomodate a huge scale of usage (high abundance). In this program, we propose to investigate the reactivity of W and/or Fe mono- and multi-metallic species bearing rigid and highly tuneable ligands, leading to carefully engineered alkane dehydrogenation catalysts that can be efficient under mild conditions. The objective of this research is not only to decrease the costs associated with the dehydrogenation of alkane process, but also to contribute to the development of greener routes to bond formation as well as to get a better understanding of the transformations occurring at the active site of enzymes.

长期以来，大自然一直是科学家和艺术家的灵感源泉。世界各地数百万人熟悉的一些设计最巧妙的产品和小玩意儿，都归功于在植物和野生动物中发现的看似简单的形状和图案。尽管我们最近了解了大量关于自然如何进行各种有效的化学转化的信息，但生物系统是复杂的，仍然远未被完全理解。这种复杂系统的一个例子是大自然以温和的方式将大气中的氮转化为氨。100年来，氨一直是由氮气和氢气通过Haber-Bosch工艺生产的，这项技术要求非常苛刻的条件(350-550℃，150-350大气压)。相比之下，自然界中发现的一些被称为固氮酶的酶能够在常温常压下很容易地实现这种转化。由于强氮三键的断裂，碳氢化合物中强C-H键的受控活化和官能化也仍然是一个挑战。绝大多数珍贵的原材料，如液体和气态碳氢化合物，只是作为加热和运输的燃料燃烧，而这些含有C-H键的分子(烷烃和芳烃)中只有一小部分被大规模转化为化学中间体，用于化学工业。过渡金属催化的烷烃脱氢反应产生了化学工业的主要原料烯烃，是一种绿色的键构建策略。该反应允许将目前工业上使用的高活性诱变卤化起始试剂替换为简单的含C和H的化合物，并防止废物的产生。烷烃的脱氢还会产生氢气，这是一种令人垂涎的无污染能源。重要的是，由于反应的可逆性，能够使烷烃脱氢的催化剂在储氢领域有潜在的应用前景。需要开发更环保的催化剂。例如，目前工业上使用的一种技术，占北美乙烯产量的90%以上，要求温度超过800°C，每吨乙烯产生1-3吨二氧化碳。过渡金属络合物作为烷烃脱氢的均相催化剂，具有较温和的反应条件和选择性，但主要以Ir和Rh等贵金属为基础。利用自然作为灵感的来源，我们的团队将研究基于廉价金属的络合物，这些金属传统上被忽视以实现烷基链的脱氢，并且与许多酶的活性有关，如铁(Fe)或钨(W)。贵金属替代物的研究是C-H活化催化剂开发领域的一条新途径。避免使用贵金属将导致更便宜的催化剂，对环境和毒物的影响最小，并且可以适应巨大的使用规模(高丰度)。在这个项目中，我们建议研究带有刚性和高度可调配体的W和/或Fe单金属和多金属物种的反应性，导致精心设计的烷烃脱氢催化剂可以在温和的条件下有效。这项研究的目的不仅是降低与烷烃脱氢过程相关的成本，而且还有助于开发更环保的成键路线，以及更好地了解酶活性部位发生的转化。