Next Generation of Polyionic liquid Mixed Matrix Membranes for CO2 separation

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Development of Mixed Matrix Iongel Membranes for CO2 Separation

Publication . Nabais, Ana Rita Mileu Mota; Neves, Luísa; Tomé, Liliana; Crespo, João

The climate crisis and the strategies to mitigate it are, undoubtedly, some of the most relevant and discussed issues in today’s society. The continuous increase in greenhouse gas emissions, particularly CO2, and consequent global warming can pose severe risks to the environment and the population. Due to the urgent need to mitigate CO2 emissions, numerous strategies have been considered, particularly the implementation of a Carbon Capture, Utilization and Storage (CCUS) technology. In terms of carbon capture, membrane separation processes offer a variety of advantages, compared to other processes, in terms of lower energy consumption, maintenance requirements, and capital investment. The designable nature of Ionic Liquids (ILs) opens up a wide range of possible chemical structures, targeting specific applications, especially CO2 capture processes. Considering the broad range of tunable chemical and physical properties of ILs and the undeniable advantages of membrane processes, from an economical and environmental point of view, this thesis explores the development of iongel membranes, which are a specific class of IL-based materials, for CO2 separation. Throughout this thesis, different polymer matrices and solid fillers were used to design Mixed Matrix Iongel Membranes (MMIMs) with the intent of, not only enhance their gas separation performance, but also to improve their mechanical, thermal, and chemical stabilities. A fast and solvent-free method was employed to fabricate MMIMs, by free-radical UV polymerization, as an alternative to longer and more complex preparation methods previously used. The main idea throughout the presented thesis is to fine-tune the design of iongel membranes and to address some of the major challenges regarding the use of these IL-based materials, for CO2 separation, in terms of thermal and mechanical properties and stability under different experimental conditions. In this thesis, CO2/N2 (flue gas) and CO2/CH4 (biogas) are the target separations, due to their relevance at an industrial level. Therefore, and considering the importance of evaluating the potential of the iongel membranes in a more realistic scenario, the developed materials were tested under different and relevant experimental conditions, in terms of temperature, pressure and humidity. The data presented throughout Chapters 2 to 6, clearly show that the chemistry and properties of the selected component materials has a significant impact on the MMIMs' properties and overall performance. Moreover, it is expected that the obtained results will be a step towards the design of new and alternative IL-based materials for CO2 separation.

2023Tese de doutoramento

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Poly(Ethylene glycol) diacrylate iongel membranes reinforced with nanoclays for co2 separation

Publication . Nabais, Ana R.; Francisco, Rute O.; Alves, Vítor D.; Neves, Luísa A.; Tomé, Liliana C.; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI AG

Despite the fact that iongels are very attractive materials for gas separation membranes, they often show mechanical stability issues mainly due to the high ionic liquid (IL) content (≥60 wt%) needed to achieve high gas separation performances. This work investigates a strategy to improve the mechanical properties of iongel membranes, which consists in the incorporation of montmorillonite (MMT) nanoclay, from 0.2 to 7.5 wt%, into a cross-linked poly(ethylene glycol) diacrylate (PEGDA) network containing 60 wt% of the IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][TFSI]). The iongels were prepared by a simple one-pot method using ultraviolet (UV) initiated polymerization of poly(ethylene glycol) diacrylate (PEGDA) and characterized by several techniques to assess their physico-chemical properties. The thermal stability of the iongels was influenced by the addition of higher MMT contents (>5 wt%). It was possible to improve both puncture strength and elongation at break with MMT contents up to 1 wt%. Furthermore, the highest ideal gas selectivities were achieved for iongels containing 0.5 wt% MMT, while the highest CO2 permeability was observed at 7.5 wt% MMT content, due to an increase in diffusivity. Remarkably, this strategy allowed for the preparation and gas permeation of self-standing iongel containing 80 wt% IL, which had not been possible up until now.

2021-12-20Artigo científico

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Número da atribuição

SFRH/BD/136963/2018