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Softer Frustrated Lewis Pair Catalysis for Harder Substrates: Stannyl Cations for the Hydrogenation of Carbon Dioxide to Methanol and Methyl Formate

较软的受阻路易斯对催化较硬的底物：甲锡烷基阳离子用于二氧化碳加氢为甲醇和甲酸甲酯

基本信息

批准号：
EP/N026004/1
负责人：
Andrew Ashley
金额：
$ 12.58万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FN026004%2F1
关键词：
Softer Frustrated Lewis Pair Catalysis

项目摘要

By lowering the energy barrier required for reactions to proceed, catalysts enable chemical transformations to be conducted at faster rates and with greater energy efficiency than would otherwise be possible. As such, around 90% of all processes in chemical manufacturing rely upon catalysis for effective production. Catalytic hydrogenations (the reaction of compounds with hydrogen, H2) are routinely employed in all areas of chemical production, yet the catalysts are predominantly based on precious metals (e.g. Rh, Ru, Pd, Pt) which are both expensive and of limited supply; there is therefore a strong motivation to develop new catalysts which do not incorporate such elements.In the last decade a new and exciting chemical methodology using catalysts based on inexpensive and abundant main group elements has been discovered. Known as 'frustrated Lewis pairs' (FLPs), these consist of a Lewis acid and base which (for steric and/or electronic reasons) cannot interact strongly with one another, leading to unquenched reactivity that can be exploited for the reaction with small molecules, most notably H2. When H2 reacts with FLPs it is converted into a much more reactive ionic form (protic H+ and hydridic H-) which can subsequently be delivered to substrates, hence effecting catalytic hydrogenation. To date, FLP hydrogenation catalysts almost exclusively use boron at the Lewis acidic centre, which is not optimal for the reduction of compounds containing oxygen, since the products (alcohols, water: hard bases) bind too strongly to the hard Lewis acid, which has a potent inhibitory effect on the overall rate of reaction.This proposal aims to develop new FLP-hydrogenation catalyst protocols using stannyl cations (based on [R3Sn]+ fragments), explicitly for the catalytic conversion of CO2 (carbon dioxide, a greenhouse gas) and H2 to two important commodity platform chemicals: methanol (CH3OH) and methyl formate (HCO2CH3). These can be used as feedstocks for upgrading to added-value products, or as liquid fuels. In the latter case, assuming the H2 is obtained by renewable means (e.g. photo-splitting of water using solar energy) these would represent sustainable sources of storable energy, with the potential to impact positively on the global carbon balance.This transformative approach stems from extremely encouraging initial results which show that a Bu3SnH/catalytic [Bu3Sn]+ (Bu = C4H9) system is competent for the reduction of CO2 under mild conditions, thereafter reaction with H2 liberates CH3OH, HCO2CH3 and water, in addition to the regeneration of Bu3SnH. Taken together, these results demonstrate that all stages of a catalytic cycle for CO2 hydrogenation can be achieved. Notably, the [Bu3Sn]+ catalysts are thermally stable to water, demonstrating a considerable advantage over boron-based FLPs. Currently the rate of reaction with H2 is too slow to be comparable with CO2 conversion; this will be addressed by increasing the bulk of the stannyl cations, and hence increasing their reactivity via augmented 'frustration'.

通过降低反应进行所需的能量势垒，催化剂使化学转化能够以更快的速率进行，并且具有比其他方式更高的能量效率。因此，化学制造中约90%的工艺都依赖于催化剂来实现有效生产。催化氢化（化合物与氢气H2的反应）通常用于化学生产的所有领域，然而催化剂主要基于贵金属（例如Rh、Ru、Pd、Pt），它们既昂贵又供应有限;因此，有强烈的动机开发新的催化剂，不包括这些元素。在过去的十年中，一个新的和令人兴奋的化学方法，已经发现了基于廉价和丰富的主族元素的催化剂。这些被称为“受抑刘易斯对”（FLP），由刘易斯酸和碱组成，它们（由于空间和/或电子原因）不能彼此强烈相互作用，导致未猝灭的反应性，可用于与小分子的反应，最明显的是H2。当H2与FLP反应时，它被转化为反应性更强的离子形式（质子H+和质子H-），随后可以将其传递到底物，从而实现催化氢化。迄今为止，FLP氢化催化剂几乎仅在刘易斯酸性中心使用硼，这对于还原含氧化合物不是最佳的，因为产物（酒精，水：硬碱）与硬刘易斯酸的结合太强，该提议旨在开发使用甲锡烷基阳离子的新的FLP-氢化催化剂方案（基于[R3 Sn]+片段），明确用于将CO2（二氧化碳，一种温室气体）和H2催化转化为两种重要的商品平台化学品：甲醇（CH 3OH）和甲酸甲酯（HCO 2CH 3）。这些可用作原料，用于升级为增值产品，或用作液体燃料。在后一种情况下，假设H2是通过可再生方式获得的（例如利用太阳能的光分解水）这些将代表可储存能源的可持续来源，具有对全球碳平衡产生积极影响的潜力。这种变革性的方法源于非常令人鼓舞的初步结果，这些结果表明，Bu 3SnH/催化[Bu 3Sn]+（Bu = C_4H_9）体系在温和条件下能还原CO_2，然后与H_2反应生成CH_3OH、HCO_2CH_3和水，并再生出Bu_3SnH。综上所述，这些结果表明可以实现用于CO2氢化的催化循环的所有阶段。值得注意的是，[Bu 3Sn]+催化剂对水是热稳定的，证明了相对于硼基FLP的相当大的优势。目前，与H2的反应速率太慢，无法与CO2转化率相比;这将通过增加甲锡烷基阳离子的体积来解决，因此通过增强的“阻挫”来增加它们的反应性。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Base-induced reversible H 2 addition to a single Sn( ii ) centre

碱诱导可逆 H 2 加成到单个 Sn( ii ) 中心

DOI：
10.1039/c8sc03110j
发表时间：
2018
期刊：
Chemical Science
影响因子：
8.4
作者：
Turnell-Ritson R
通讯作者：
Turnell-Ritson R

Hydrogen activation using a novel tribenzyltin Lewis acid.

DOI：
10.1098/rsta.2017.0008
发表时间：
2017-08-28
期刊：
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
影响因子：
0
作者：
Cooper RT;Sapsford JS;Turnell-Ritson RC;Hyon DH;White AJP;Ashley AE
通讯作者：
Ashley AE

Supporting Information from Hydrogen activation using a novel tribenzyltin Lewis acid

使用新型三苄基锡路易斯酸进行氢活化的支持信息