Helium recovery from LNG waste stream using two-dimensional nanostructured MXene membranes

氦气（He）是一种战略性工业气体，在广泛的高科技应用中发挥着越来越重要的作用。目前全球对He的需求为4%。每年2亿立方米（STP），价值60亿美元。从氮气和微量CH4和CO2中分离He的主要目标仅通过低温蒸馏（高能量和资本密集型工艺）完成，然后在木炭上吸附，将He纯度提高到99.95%。该项目旨在开发无机中空纤维支撑的纳米结构二维MXene膜，作为先进的功能材料，用于从其与N2和微量CH4、CO2的混合物中分离He，用于液化天然气（LNG）工厂的He回收。该研究的关键概念是以材料科学为导向，旨在合成具有可控孔径的层状二维MXene膜，将其组装在多孔无机中空纤维载体上，在室温下提供>000 Barrer的高He渗透率，并对其他气体具有bbb30的选择性。这些渗透参数允许在一级渗透过程中产生99%纯度的He，而不是冷冻精馏，从而为最终吸附过程提供合适的进料。科学挑战将是直接合成MXene纳米片或通过多层MXene粉末分层制备MXene纳米片。另一个关键步骤是将纳米片沉积在支架上，以获得可控的孔径。在实际应用中，MXene膜将在陶瓷或不锈钢等无机中空纤维支架上制备，因为中空纤维的几何形状可以提供单位体积的最大膜面积。具体来说，这个项目的目标是：(1)合成和功能化MXene纳米片；(2)通过优化MXene膜的层间距和MXene纳米片的片状尺寸，实现He选择性和通量的最大化；(3)通过组装的二维纳米结构MXene膜了解气体的输运行为。

Helium (He) is a strategic industrial gas which becomes increasingly important within a wide range of high-tech applications. The current global demand for He is appr. 200 Mio m3 (STP) per annum with a value of US$ 6 billion. The primary objective of the separation of He from N2 and trace amounts of CH4 and CO2 has been accomplished solely by cryogenic distillation - a highly energy and capital intensive process - followed by an adsorption on charcoal increase the He purity up to > 99.95%. This project aims to develop inorganic hollow-fiber supported nanostructured 2D MXene membranes as advanced functional material for He separation from its mixture with N2 and trace amounts of CH4, CO2 for He recovery in liquefied natural gas (LNG) plants. The key concept of the research is material science-oriented and aims at the synthesis of layered 2D MXene membranes with controlled pore sizes to be assembled on porous inorganic hollow-fiber support, delivering high He permeability of > 1000 Barrer with a selectivity of He against other gases of > 30 at room temperature. These permeation parameters allow to produce 99% pure He in a 1-stage permeation process instead of the cryo-distillation thus giving a suitable feed for the final adsorption process. The scientific challenges will be the direct synthesis of MXene nanosheets or their preparation by delamination of multilayer MXene powder. Another crucial step will be the deposition of the nanosheets on supports to get a controllable pore size. For practice application, the MXene membrane will be prepared on inorganic hollow-fiber supports like ceramic or stainless steel material as the hollow fibre geometry can provide the largest membrane area per unit volume. Specifically, the objectives of this project are to (1) Synthesise and functionalise MXene nanosheets; (2) Maximize He selectivity and flux by optimizing the interlayer spacing of the MXene membranes and the flake size of the MXene nanosheets; (3) Understand the gas transportation behaviour through the assembled two-dimensional nanostructured MXene membranes.