Chemisorbent Materials for Olefin/Paraffin Separation

丙烯和乙烯通常用于食品包装和化学品等。为了跟上丙烯和乙烯产品需求的增长，轻质烯烃的产量也必须增加目前，最可行的途径是原油精制制备。石油化工工业从原油中生产烯烃（乙烯和丙烯）原油经过加工后，有烯烃和低链烷烃的混合物。因此，需要一个分离过程来分离烯烃和石蜡。混合物对工业没有用处。就丙烯而言，有三种不同的等级：聚合物级纯度最低为99.5%，化学级纯度最低为93-94%，炼油厂级纯度最低为60%。分离烯烃和石蜡的标准方法是低温蒸馏例如，丙烯和丙烷的分离是困难的，因为这两种气体具有非常相似的沸点（丙烯为-47.6摄氏度，丙烷为-42.1摄氏度），因此，需要能够在低温和高压下保持的精馏塔。然而，低温蒸馏是一个能源密集型的过程。通常，低温精馏塔在-40摄氏度和-90摄氏度之间的温度下操作150-200个托盘，压力范围从16到20巴为了了解能量的数量，2016年生产每公吨乙烯需要20吉焦耳的能量。这平均相当于2016年一个人在英国生活一年所需的能量。14即使有这么大的能量需求，自20世纪60年代引入以来，低温蒸馏仍然是首选的分离方法。文献中已经报道了基于传质系统而不是能量传递方法的替代分离方法，然而，围绕这些系统的实施仍然存在问题，导致公司不愿将其纳入其过程。替代品包括银和铜盐、膜、金属有机框架、沸石咪唑盐框架。15-19本项目的重点将放在离子液体替代品上。离子液体一直是气体分离和俘获领域的研究热点这是由于它们可以带来的独特特性，如可忽略不计的蒸汽压，高热稳定性和大的液相范围。22-24此外，它们可以被修饰，离子液体的物理化学性质可以很好地调整，因此它们被称为“设计溶剂”。然而，一些离子液体的限制因素包括它们的低气体溶解度、分离选择性和高粘度。该项目旨在开发和测试新的化学吸附剂（在溶质和离子液体之间形成强相互作用）。这些相互作用通常是不可逆地结合到表面)的材料，用于分离轻质烯烃和石蜡。此外，该项目将专注于设计、开发和测试一个天然气钻井平台，以测试这些材料在模拟工业条件下分离烯烃和石蜡气体的能力。该设备允许气体混合物与离子液体接触，并通过顶空气相色谱法监测气体成分随时间的变化，直到达到平衡（并确定平衡时间）。实验将以纯（单一）气体、烯烃和石蜡的二元混合物以及随后存在的污染物进行，以模拟蒸汽裂解后获得的气流。可用的引用。

Propylene and ethylene are commonly employed for food packaging, and chemicals amongst others.1-4 To keep pace with a greater demand for propylene and ethylene products, the production of light olefins must also therefore increase.3 Currently, the most feasible route is preparation via the refinement of crude oil. 5The petrochemical industry produces olefins (ethylene and propylene) from crude oil.7 After the processing of the crude oil, there is a mixture of olefins and lower chained paraffins. Therefore, a separation process is required to separate the olefins and paraffins. A mixture is not useful to industry. In terms of propylene there are three different grades: polymer grade is a minimum of 99.5% purity, chemical grade a minimum of 93-94% purity, and a refinery grade with a minimum of 60% purity. The standard method used for the separation of olefin and paraffins is cryogenic distillation.6 For example, propylene and propane separation is difficultas both gases have very similar boiling points, (-47.6 degree centrigrade for propylene and -42.1 degree centrigrade for propane),10 thus, distillation columns that can be maintained at low temperatures and high pressures are required. However, cryogenic distillation is an energy intensive process. Generally, cryogenic distillation columns operate with 150-200 trays at temperatures between-40 degree centrigrade and -90 degree centrigrade with pressures ranging from 16 to 20 bar.13 To understand the quantity of energy, every metric ton of ethylene produced in 2016, 20 Gigajoules of energy was required. That, on average is the same value of energy required for an individual to live in the UK for one year in 2016.14Even with this large energy requirement, cryogenic distillation is still the preferred method of separation since its introduction in the 1960s. Alternative separation methods have been reported in the literature, based on mass transfer systems instead of the energy transfer methods, however, there are still issues surrounding the implementation of these systems, resulting in the reluctance of companies to adopt them into their processes. Alternatives have included silver and copper salts, membranes, metal organic frameworks, zeolite imidazolate frameworks.15-19 The focus of this project will focus upon the ionic liquid alternative.Ionic liquids have been the focus of great interest in the field of gas separation and capture.20 This is due to the unique properties they can bring such as negligible vapor pressure, high thermal stability, and large liquidus range.22-24 Furthermore, they can be modified and the physical-chemical properties of ionic liquids can be finely tuned, and so they have been named as "designer solvents". However, the limiting factor for some ionic liquids include their low gas solubilities, separation selectivities, and high viscosities.25This project aims to develop and test new chemisorbent (forming strong interactions between the solute and the ionic liquid. These interactions are usually irreversibly bound to the surface) materials for the separation of light olefins and paraffins. Furthermore, this project will focus on the design, development, and benchmark of a gas rig to test the ability of these materials to separate olefin and paraffin gases, whilst mimicking industrial conditions. The equipment allows the gas mixture to come into contact with the ionic liquid, and the gas composition change over time being monitored by headspace gas chromatography, until equilibrium is reached (and equilibrium time determined). Experiments will be carried out with pure (single) gas, binary mixtures of olefin and paraffin, and subsequently with contaminates present, to mimic gas streams obtained after steam cracking.References available.