(557b) Crosslinked Thin Film Composite Membranes for Industrial Organic Complex Mixtures Separations

Organic solvent separations, which are commonly used in the chemical, petrochemical, and pharmaceutical industries, are energy-intensive processes. Membrane technology can potentially reduce the energy and resources needed for these separations, but it can be less effective when separating highly similar molecules. Some polymers used in organic solvent reverse osmosis (OSRO) have been known to suffer from plasticization and dilation, making them inefficient for these molecular separations. One solution to this issue is to crosslink the polymer used in the membrane, but traditional methods, such as solvent swelling methods, can be limited by the diffusional movement of the crosslinking agents, and this effect becomes more pronounced as crosslinking agents become bulkier. We have developed a method to introduce larger crosslinking agents to the membrane while overcoming diffusional limitations during the crosslinking infusion step. We utilize the commercial polymer Matrimid® 5218 and four crosslinking agents: para-xylylene diamine, 4,4’-biphenyldicarbontrile, spirobifluorene, and triptycene. We introduce a novel Boc protection method to the amines to enable dissolution of the crosslinkers into the membrane casting solution. After casting, the amines within the membrane are thermally deprotected to induce a solid-state crosslinking reaction. The resulting membranes were characterized by FT-IR, gel fraction, helium pycnometry, and TGA. The separations performance was tested in a crossflow OSRO permeation system for a toluene/triisopropyl benzene system and a multicomponent organic solvent mixture. Beyond that, we tested these membranes for performance in a real crude tall oil and crude sulfate turpentine feed. The results showed that the crosslinked TFC membranes had excellent stability in organic solvents and challenging real-world mixtures. Furthermore, the membrane performance could be fine-tuned for separation based on the crosslinking agent and its concentration.