Hybrid Layered Double Hydroxides for CO2 Conversion to Useful Chemicals

由于人类活动，包括开采和燃烧化石燃料以获取能源，以及在日常生活中制造一系列产品，大气中的二氧化碳(CO2)水平已升至400ppm以上。为了过渡到净零度并将气温上升保持在《巴黎协定》1.5摄氏度以下的目标，提出了两种方法--通过可再生能源减少排放，以及从大气中消除二氧化碳。二氧化碳从大气中去除后，可储存或用作化学合成的原料，例如制造聚合物或甲醇。甲醇是最简单的酒精，只有一个碳原子组成，可以用作清洁燃料，只排放二氧化碳和水，与化石燃料的燃烧相比，其他有毒气体或烟尘的排放量要小得多。目前，甲醇是在相对较高的温度和压力下，在金属催化剂上通过重整天然气产生的合成气生产的。然而，目前正在寻求替代的、更可持续的方法。如果可以从捕获的二氧化碳和可再生氢气中合成甲醇，整个过程就会变成碳中性。此外，甲醇是化学工业生产一系列更复杂分子的有用原料，也被用作溶剂。这反映在全球甲醇产量上，2018年达到8500万吨，足以每12分钟填满一个奥运会游泳池。层状双氢氧化物(LDHs)是一种离子固体，其结构基于天然矿物水滑石。它们是由带正电的层组成的，这使得一系列带负电的离子可以插入到层间空间中。能够改变分层结构中的元素和可以插入其中的化学物质，这意味着研究人员可以根据特定的应用来定制它们的性质。从吸附到塑料添加剂再到药物输送的载体，LDH也可以被用作催化剂，这些材料可以加速化学反应，或者首先使化学反应发生。近年来，LDHs已被用于催化氢气与二氧化碳加成，生成甲醇，但总收率较低。该项目旨在合成更多包含不同金属的LDH材料，并将其用于二氧化碳催化加氢生产甲醇。与以前在这一领域的工作相比，这些工作的目的是提高二氧化碳的转化率和选择性，从而增加整体甲醇产量。该项目属于EPSRC制造未来和物理科学主题。

Carbon dioxide (CO2) levels in the atmosphere have risen to over 400 ppm, as a result of human activities including the extraction and burning of fossil fuels for energy, and in the manufacture of a range of products in everyday life. In order to transition to net zero and keep temperature rises below the 1.5oC target of the Paris Agreement, two approaches are proposed - reduction in emissions through renewable sources of energy, and removal of CO2 from the atmosphere. Upon removal from the atmosphere, CO2 can be stored or used as a feedstock in chemical synthesis, for example for polymers or methanol.The concept of the methanol economy was proposed by George A. Olah in the 1990s. Methanol is the simplest alcohol, composed of only one carbon atom, and can be used as a clean fuel, emitting only CO2 and water, and much smaller amounts of other toxic gases or soot compared to the combustion of fossil fuels. Methanol is currently produced from syngas, generated by reforming natural gas, over a metal catalyst at relatively high temperatures and pressures. However, alternative, more sustainable methods are currently being pursued. If methanol can be synthesised from captured CO2 and renewable hydrogen, this whole process becomes carbon neutral. In addition, methanol is a useful feedstock to the chemical industry to produce a range of more complex molecules, and is also used as a solvent. This is reflected in the global production of methanol, which reached 85 million tonnes in 2018, enough to fill an Olympic swimming pool every twelve minutes.Layered double hydroxides (LDHs) are a class of ionic solid with a structure based on that of the naturally occurring mineral hydrotalcite. They are made of positively charged layers, which allows a range of negatively charged ions to be inserted in the interlayer space. The ability to vary the elements in the layered structure and the chemicals that can be inserted between means their properties can be tailored by researchers towards specific applications. These can range from adsorption to plastic additives to vehicles for drug delivery.LDHs are also able to be used as catalysts, materials which speed up a chemical reaction, or enable it to occur in the first place. Recently, LDHs have been used to catalyse the addition of hydrogen gas to carbon dioxide, producing methanol, however with low overall yield. This project aims to synthesise more LDH materials incorporating different metals, which will be tested for the catalytic hydrogenation of carbon dioxide to produce methanol. Compared to previous work in this area, these will aim to have improved CO2 conversion and selectivity, and therefore increased overall methanol yield.This project falls within the EPSRC manufacturing the future and physical sciences themes.