Gas Adsorption at Structured Ionic Liquid Surfaces

结构化离子液体表面的气体吸附

基本信息

批准号：
EP/I018093/1
负责人：
Robert Jones
金额：
$ 71.75万
依托单位：
University of Nottingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FI018093%2F1
关键词：
Gas Adsorption Structured Ionic Liquid

项目摘要

The absorption, or capture, of gases into liquids has been studied since the early 1800's. However, the study of liquid surfaces has been restricted to techniques that can operate at or near to atmospheric pressure because common liquids have high vapour pressures (>10-6 mbar), due to the relatively weak van der Waals interactions that hold them together as liquids. This meant that liquid surfaces could not be studied (with some exceptions) on the molecular scale because such study requires the use of powerful, vacuum based, surface science techniques developed for solid surfaces over the past half century. However, ionic liquids, consisting of relatively large, low symmetry, organic cations, matched with inorganic or organic anions, have ultra low vapour pressures at room temperature (<10-10 mbar), due to the strongly cohesive Coulomb potential between the ions, making them vacuum compatible. Therefore, the liquid surfaces of ILs can be studied with molecular detail using vacuum based surface science techniques, opening up a new field of liquid surface science. Our goal is to quantitatively determine the surface structure of ionic liquids, and relate that structure to how gases adsorb onto the surface layers and then pass by absorption into the bulk of the ionic liquid. There are good academic and industrial reasons for such work. Academically, because ionic liquids are composed of large complex species, they have the potential for a level of surface self-organisation that is completely beyond anything simple solvents can attain. The most obvious examples of this self organisation are surface freezing, where long alkyl chains align themselves at the surface into a semicrystalline layer (thus providing an oleaginous barrier to adsorbing gas), and the formation of an ionic underlayer where the charge carriers of the anion and cation form a charged double layer which can act as a surface trap for adsorbed species. By understanding how such self-organisation depends on the nature of the IL, and how the self-organised structure then affects the adsorption of gases, we open up a new area of task specific liquid surface science. Crucially, the ultra-low volatility of ionic liquids is also the property that gives them their huge industrial potential, because the IL does not contaminate gas phase reactants and products with its vapour. Of particular relevance to this application is the SILP (surface ionic liquid phase) process, which combines the advantages of homogeneous and heterogeneous catalysis, and the possibilities of using ILs as capture agents for CO2 in carbon capture and storage (CCS). In this application we use the low volatility of ILs to apply ultra-high vacuum surface science techniques to their surfaces. Surface structures will be determined using angle resolved XPS and X-ray reflectivity, while surface kinetics will be determined using line of sight mass spectroscopy to measure absolute sticking probabilities and temperature programmed desorption. Our work will be the first coherent study of adsorption of any type on well defined liquid surfaces, and will be seminal in the development liquid surface science, comparable to the advances in understanding of solids surfaces when ultra-high vacuum adsorption studies were first carried out in the late '60s and early '70s.Longer term (15-30 years) we will start to answer more complex questions such as; how can this highly structured, anisotropic, but mobile, surface environment be deliberately modified to facilitate the formation of nanostructures using material from both sides of the surface; can we design new types of liquid surfaces which will facilitate directed self assembly of nanoparticles and nanomachines; can we begin to engineer liquid membranes with embedded moieties similar to those in living cells?

自 1800 年代初期以来，人们就开始研究将气体吸收或捕获到液体中。然而，液体表面的研究仅限于能够在大气压或接近大气压下运行的技术，因为普通液体具有较高的蒸气压（>10-6 mbar），这是由于将它们结合在一起的范德华相互作用相对较弱。液体。这意味着液体表面无法在分子尺度上进行研究（有一些例外），因为此类研究需要使用过去半个世纪为固体表面开发的强大的、基于真空的表面科学技术。然而，离子液体由相对较大、低对称性的有机阳离子组成，与无机或有机阴离子相匹配，由于离子之间具有强内聚库仑势，因此在室温下具有超低蒸气压（<10-10 mbar），使它们与真空兼容。因此，可以使用基于真空的表面科学技术对离子液体的液体表面进行分子细节研究，开辟了液体表面科学的新领域。我们的目标是定量确定离子液体的表面结构，并将该结构与气体如何吸附到表面层然后通过吸收进入离子液体的主体相关联。此类工作有充分的学术和工业理由。从学术上讲，由于离子液体由大型复杂物质组成，因此它们具有完全超出任何简单溶剂所能达到的表面自组织水平的潜力。这种自组织最明显的例子是表面冻结，长烷基链在表面排列成半结晶层（从而为吸附气体提供油质屏障），以及离子底层的形成，其中阴离子的电荷载体和阳离子形成带电双层，可以充当吸附物质的表面陷阱。通过了解这种自组织如何取决于离子液体的性质，以及自组织结构如何影响气体的吸附，我们开辟了任务特定液体表面科学的新领域。至关重要的是，离子液体的超低挥发性也赋予了它们巨大的工业潜力，因为离子液体不会以其蒸气污染气相反应物和产物。与该应用特别相关的是 SILP（表面离子液体相）工艺，它结合了均相和多相催化的优点，以及在碳捕获和储存 (CCS) 中使用离子液体作为 CO2 捕获剂的可能性。在此应用中，我们利用离子液体的低挥发性将超高真空表面科学技术应用于其表面。表面结构将使用角度解析 XPS 和 X 射线反射率来确定，而表面动力学将使用视线质谱法来确定，以测量绝对粘附概率和程序升温解吸。我们的工作将是第一个对明确液体表面上任何类型的吸附进行连贯研究，并将对液体表面科学的发展产生重大影响，堪比首次进行超高真空吸附研究时对固体表面理解的进步在 60 年代末和 70 年代初。长期（15-30 年）我们将开始回答更复杂的问题，例如；如何故意修改这种高度结构化、各向异性但可移动的表面环境，以促进使用表面两侧的材料形成纳米结构；我们能否设计新型液体表面，以促进纳米颗粒和纳米机器的定向自组装？我们可以开始设计具有类似于活细胞中的嵌入部分的液膜吗？