Oil refining is necessary for transforming raw, unusable crude oil into valuable goods like gasoline, diesel, jet fuel and petrochemical feedstocks. However, the usual distillation process is energy-intensive, spurring researchers to find better, more efficient ways of refining oil. A new study published in Science describes a potential solution to this problem in the form of a specialized membrane. So far, these membranes are proving to be a scalable and highly plausible industrial technology, and testing has shown promising results for significantly reducing the energy needs of oil processing.
The problem with distillation methods
Oil refineries mostly rely on continuous fractional distillation to separate crude oil into different hydrocarbon fractions based on their boiling points. The process uses around 11% of the extracted oil energy. To make matters worse, this process is incapable of separating hydrocarbons with similar boiling points and distinct chemical structures. To separate these components, additional secondary processes must be used, further complicating oil refining.
One important industrial need is separating aliphatics (chain-like molecules) from aromatics (ring-like molecules) for crude oil-to-chemicals pathways. Aromatics like benzene, toluene and xylene are often used in consumer products, but the similar boiling points of aliphatics and aromatics mean they are difficult to separate via distillation.
Polymer membranes have been used to improve crude-oil fractionation, but they typically trade off throughput for chemical selectivity. The authors of the new study write, "Attempts using membranes such as polytriazole, hydrophobic polyamine, poly(arylene amine), microporous polyimine, and commercial oNF-2 have achieved impressive progress in enriching low molecular weight components, but all suffered from low permeance and poor selectivity for specific hydrocarbon classes, largely due to the difficulty of precisely tuning pore structure and functionality in conventional amorphous polymer membranes."
A better high-performance membrane
The team involved in the new study focused on a class of membranes called covalent organic frameworks (COFs), which are membranes made of crystalline porous polymers with changeable pore structures and versatile chemistry. Earlier studies on COF membranes showed high performance with certain separations, but not with strong class-specific crude-oil separation. They also struggled with scalable fabrication.
But the team was able to overcome some of these hurdles. They designed a series of COFs with increasing alkyl chain length capable of tuning pore size and oil affinity. This resulted in crystalline COF membranes with sub-nanometer pores and alkyl (oil-like) functional groups that preferentially pass aliphatics.
"Whereas metal-organic framework (MOF)-based mixed matrix membranes have enriched aromatics from simplified model mixtures under vapor-phase pervaporation, our COF membranes enable selective aliphatic enrichment from complex crude oil in a fully liquid-phase process, reducing energy demand compared with thermal separations," the study authors explain.
Pilot tests and scalable manufacturing
The researchers tested the performance of a series of COFs with increasing alkyl chain length, referred to as COF-Me, COF-But and COF-Hex, on a synthetic 10-component mixture and then on undiluted, unheated Arabian Light crude oil under crossflow filtration. In the synthetic mixture, the aliphatic content in permeate rose to 88.2%, 93.9% and 94.2% for COF-Me, COF-But and COF-Hex, respectively.
The study authors write, "COF-Me exhibited modest aliphatic enrichment and partial aromatic rejection, with rejection values of 36.3% for toluene, 54.1% for pyrene, and 56.1% for benzo[ghi]perylene. With longer alkyl chains, COF-But and COF-Hex displayed markedly improved performance: Light aliphatics were enriched, whereas aromatics and larger aliphatics were effectively retained."
In tests with the Arabian Light crude oil, a two-stage membrane series boosted aliphatic content from 54.5% in the feed to 92.0% in stage 1 and 96.1% in stage 2. The membranes strongly rejected aromatic classes in the crude oil. Stage 1 rejected 72.2% of benzenes and ~94–95% of naphthalenes and PAHs, improving further in stage 2.
Then the team demonstrated scalable roll-to-roll manufacturing, creating a continuous 50-meter-long (164-foot-long), 0.3-meter-wide (1-foot-wide) membrane sheet using an electric field–assisted process to deposit COF layers onto porous polymer supports. They then tested a pilot-scale separation system for direct aliphatic separation from Arabian Light crude oil. The industrial-style spiral-wound modules enriched aliphatics to 90.2% in one stage, running stably for more than 250 hours. Importantly, energy needs were only about 20.7 MJ per barrel, far lower than the 50–200 MJ per barrel typical in distillation, suggesting large potential energy savings.
The study authors write, "Membrane filtration accounted for ~57.4% of the total energy input. Notably, the present pilot-scale membrane energy consumption represents a conservative baseline, as it does not include pressure-energy recovery, indicating substantial room for further reduction at industrial scales."
The team says the results represent strong potential for membrane-based processes as scalable, energy-efficient alternatives to thermal separations like distillation. Future studies may improve selectivity further to approach narrower cuts or single-component separations, which would likely require multistage or cascade designs. The researchers do note that some flux decline occurred over time because of fouling, but it was reversible with cleaning.
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Publication details
Li Cao et al, Scalable fabrication of COF membranes for aliphatic/aromatic separation of crude oil, Science (2026). DOI: 10.1126/science.aea0869
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Citation: Next‑generation membranes can refine crude oil using under half the energy of distillation (2026, July 9) retrieved 13 July 2026 from https://phys.org/news/2026-07-nextgeneration-membranes-refine-crude-oil.html
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