Base metal catalysis of acceptorless alcohol dehydrogenation for hydrogen storage

贱金属催化无受体醇脱氢储氢

• 批准号: 2750887
• 金额: --
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2750887
• 关键词: Base; metal; catalysis; acceptorless; alcohol

Catalytic acceptorless alcohol dehydrogenation is an atom-economical approach for alcohol oxidation without the need for an oxidant. Reversible dehydrogenation/hydrogenation catalysis from this reaction provides a route to the use of organic molecules derived from biomass as liquid organic hydrogen carriers (LOHCs). Alcohols such as ethylene glycol, glycerol and the C4-C6 analogues erythritol, xylitol, and sorbitol are considered to be potentially useful biomass-derived feedstocks since they can be derived from agricultural or lumber resources, including waste streams and their gravimetric hydrogen storage capacities (Figure 1) meet targets set by the EU and the US Department of Energy. This chemistry has long been dominated by the platinum group metals (PGMs), with an elegant recent example being the report of a reversible liquid to liquid organic hydrogen carrier system using ethylene glycol and a ruthenium pincer complex. However, the low abundance of PGMs leads to high economic and environmental cost, and their high toxicity means that their removal from products often is required, producing significant waste streams. It is therefore essential that researchers look to other catalysts for industrial processes, with obvious candidates being base metals that exhibit low cost, high natural abundance, uniform global distribution and low toxicity. This project will investigate a range of low-coordinate and pincer complexes of the first-row transition metals in order to achieve the acceptorless dehydrogenation reactions, and, with appropriate candidates, investigate the possibility of undertaking the reverse reaction with addition of H2. The first- row transition metals, with their low metal-ligand bond strengths are excellent candidates to achieve alcohol dehydrogenation reactions, as net oxidation requires dihydrogen loss from the metal. Pincer ligands have been shown to promote excellent stability and reactivity in acceptorless alcohol dehydrogenation reactions with first-row transition metal complexes, and metal-ligand cooperativity that has been successful using PGM catalysts, which may also be investigated for the base metals as the project progresses. Our recent research has revealed that complexes featuring cheap, non-toxic and earth abundant base metals can catalyse a range of reactions, including dehydrogenation and hydroelementation reactions. In terms of the proposed alcohol substrates, we envisage challenges such as differing reactivity with substitution at the hydroxyl residues and the catalysis of the reaction with H2 (reverse reaction), allowing a closed cycle for LOHC technology. Judicious choice of catalyst (or pre-catalyst), including the metal and ligand, and reaction conditions will facilitate the acceptorless alcohol dehydrogenation reactions with efficiency and product selectivity. Determination of reaction mechanisms through spectroscopic, structural and kinetic investigations allows the optimisation of the reactions. It is envisaged that investigations will also allow improvements in the temperatures, solvents (including a range of biomass-derived solvents) and catalyst loadings required for hydrogen release, but also the selectivity (e.g. avoidance of any undesirable by-products). The student will benefit from training in chemical techniques (e.g. organometallic chemistry, spectroscopy, crystallography and kinetic investigations) and principles of sustainable chemistry.

催化无受体乙醇脱氢是一种不需要氧化剂的原子经济的乙醇氧化方法。该反应的可逆脱氢/加氢催化提供了一条将来自生物质的有机分子用作液体有机氢载体的途径。乙二醇、甘油和C4-C6类似物赤藓糖醇、木糖醇和山梨醇等醇被认为是潜在有用的生物质衍生原料，因为它们可以从农业或木材资源中获得，包括废流及其重量氢储存能力(图1)，达到了欧盟和美国能源部设定的目标。这一化学长期以来一直由铂族金属(PGMS)主导，最近的一个很好的例子是报道了一种使用乙二醇和Ru钳形络合物的可逆液-液有机氢载体体系。然而，PGMS的低丰度导致了高昂的经济和环境成本，而且它们的高毒性意味着它们经常需要从产品中去除，产生大量的废物。因此，研究人员必须寻找其他用于工业过程的催化剂，明显的候选对象是成本低、自然丰度高、全球分布均匀和低毒的贱金属。本项目将研究一系列第一排过渡金属的低配位和钳形配合物，以实现无受主脱氢反应，并与合适的候选者一起，研究进行加氢的反向反应的可能性。第一排过渡金属具有较低的金属-配体键强度，是实现醇脱氢反应的极好候选者，因为净氧化需要金属中的二氢损失。钳形配体已被证明在无受体乙醇脱氢反应中与第一排过渡金属络合物的反应具有良好的稳定性和反应活性，并已成功地用于PGM催化剂，这也可能随着项目的进展而对贱金属进行研究。我们最近的研究表明，具有廉价、无毒和富含贱金属的配合物可以催化一系列反应，包括脱氢反应和氢化元素反应。就所建议的乙醇底物而言，我们预计将面临挑战，例如与羟基残基上的取代反应的不同反应活性以及与氢的反应的催化(反向反应)，从而允许LOHC技术的闭合循环。合理选择催化剂(或前催化剂)，包括金属和配体，以及反应条件，将有助于无受体乙醇脱氢反应的效率和产物的选择性。通过光谱、结构和动力学研究确定反应机理，可以优化反应。预计调查还将允许改善放氢所需的温度、溶剂(包括一系列生物质衍生溶剂)和催化剂负载量，以及选择性(例如，避免任何不良副产品)。学生将从化学技术(如有机金属化学、光谱学、结晶学和动力学研究)和可持续化学原理方面的培训中受益。