Op maat gemaakte membraanoplossingen voor olefin/paraffin gasscheidingen

Olefins remain indispensable raw materials for the chemical industry, serving as building blocks in the production of polyolefin plastics and other base chemicals. Despite the emergence of alternative technologies for olefin synthesis routes, the current dominant technology for olefin production is still expected to be pioneering in this field, necessitating the separation of olefins from paraffins in product streams. Nevertheless, conventional separation technologies primarily adapted for these separations pose a major burden on global energy consumption and associated emissions. Within this direction, the main objective of this dissertation includes to design and develop novel membranes with improved performance for efficient light olefin/paraffin separations, more specifically for the separation of ethylene/ethane (C2) and propylene/propane (C3) gas mixtures. Given the challenging nature of such separations, this dissertation investigates three distinct membrane types to examine membrane-based olefin/paraffin gas separation from a broader perspective: (i) integrally skinned asymmetric (ISA) membranes, (ii) mixed-matrix membranes (MMMs), and (iii) supported liquid membranes (SLMs). The first part of the dissertation concentrates on the development of 6FDA-based ISA membranes prepared via nonsolvent-induced phase separation (NIPS). One of the primary focuses of this research was to scrutinize eco-friendly solvent alternatives for polymer dissolution to alleviate the environmental concerns surfaced regarding the generation of toxic solvent-laden air and spent baths during NIPS. Besides, intending to evince a synthesis-structure-performance relationship, the casting solution formulation was methodologically studied to appraise the effect of volatile cosolvents and nonsolvent additives on membrane morphology and separation performance. After obtaining defect-free membranes through casting solution optimization, the membranes were decorated with silver to enhance their affinity for olefins. In addition to the improved membrane performance due to π-complexation between olefins and silver ions, the results further demonstrated that the separation of these gas pairs is largely characterized by the diffusion selectivity of the membranes. While offering critical insights into the complex interplay of NIPS parameters on membrane morphology and performance, this study also constitutes a stride forward in adopting more sustainable practices in membrane development. Next, a series of MMMs were investigated by incorporating derivatives of MOF-808, a highly tunable and robust zirconium-based metal-organic framework, into a 6FDA-based polymer matrix. Initially, MMM performance was systematically linked to key synthesis parameters such as polymer concentration, filler amount and solvent properties. The most suitable MMM preparation protocol was determined, representing a significant step towards the preparation of defect-free membranes demonstrating high performance and ease of handling. Aiming to exploit the high affinity of transition metals towards olefins to improve MMM performance, copper was incorporated into MOF-808 via post-synthesis modifications. However, MMMs filled with copper-incorporated MOF-808 exhibited lower olefin permeability values compared to MMMs prepared using pristine MOF-808. The lower olefin/paraffin selectivity implied a reduced permeation rate for olefins due to their strong affinity for the introduced adsorption sites in MOF-808 cages, suggested by the observed high adsorption enthalpies of olefins in copper-containing MOF-808. Motivated by this, an opposite approach was adopted, targeting higher affinity for paraffins over olefins. To this end, fluorinated carboxylic acid modulators were employed to synthesize MOF-808 samples. Despite the improvement in gas permeability observed for both C2 and C3 mixtures as a result of imparting porosity to the membranes upon the incorporation of these filler particles, the desired increase in selectivity was attained only in C3 separation. Here, the difference in separation performance exhibited by the membranes against C2 and C3 mixtures was attributed to the fact that C3 gases have more restricted mobility across the membrane due to their larger molecular size compared to C2 gases. Therefore, the large cavity of MOF-808 limited the ultimate selectivity for C2 gases to the diffusion selectivity displayed by the polymer phase of the MMMs. Due to the preferential sorption of propane, on the other hand, a significant enhancement in propylene/propane selectivity was achieved when incorporating fluorinated fillers. These results thus delineate an important aspect of the relationship between the compatibility of permeation properties of coupled polymer and filler materials for target gas pairs and the resulting MMM performance. Finally, interfacial transport (IT) was introduced as a novel strategy for the preparation of SLMs, leveraging the difference in affinity of the liquid of interest to the organic and aqueous phases. The selective compound concentration and contact time required for its deposition into the support pores were identified as key synthesis parameters, and their effects on the formation of thin-film SLMs were elucidated. The variable selection of solvents used during membrane preparation and the stable performance of the prepared SLMs at high pressures substantiated the versatility of IT. This newly established strategy was further exploited to incorporate silver ions into SLMs to facilitate the transport of olefins. In order to acquire the most promising performance from these SLMs, various silver salt sources and concentrations, as well as different silver incorporation strategies, were examined. The developed membranes demonstrated not only enhanced separation performance but also long-term operational stability. It is believed that the potential of the IT strategy can be further advanced by utilizing the findings of this research as a framework for preparing high-performance SLMs to be developed for various gas separation applications.