Designing membrane systems for the direct separation of multicomponent organic solvent mixtures

Abstract

The membrane separation paradigm, free from phase change, aligns with global carbon reduction goals by offering an energy-efficient alternative to current thermal industrial separations. Operating based on the permeation rate ratio, the membrane separation process eliminates latent heat requirements, reducing energy consumption by up to 10%. It thereby shows promise in lowering carbon emissions and finds applications in diverse industries such as pharmaceuticals and petrochemicals, serving as a potential replacement for solvent separation processes. Despite its potential, membrane separation processes face challenges in achieving economically feasible high throughput and selectivity, especially when dealing with complex multi-component mixtures during separation and purification. This dissertation proposes an innovative methodology for directly separating organic solvent mixtures at room temperature, spanning from bulk mixture separation to molecular-level differentiation. The approach considers membrane materials and explores new separation methodologies tailored to specific separation targets. Leveraging an understanding of adsorption and diffusion behavior, the ultramicroporous carbon hollow fiber membrane is designed with pores similar in size to solvent molecules. Such design achieves size and shape selectivity, enabling sub-angstrom resolution in room temperature organic solvent forward osmosis technology using a draw solvent, a demonstration accomplished for the first time. Additionally, the study emphasizes the potential of pressure-assisted osmosis technique to simultaneously achieve high throughput and selectivity for challenging hydrocarbon liquids by controlling process conditions, including the type of draw solvent. Finally, it accomplishes a membrane-based reverse osmosis process for complex organic solvent mixtures, specifically crude oil containing over a thousand components, and proposes design orientations for a continuous membrane cascade to comprehensively replace conventional distillation-based separation processes.