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

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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.