Ultrathin membranes could transform hydrocarbon processing by slashing energy use

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A team of international researchers has developed a new class of ultrathin polymer membranes that can rapidly and selectively separate complex hydrocarbon mixtures, potentially transforming how crude oil is refined and refinery streams are processed, significantly reducing the energy required for one of the world's most energy-intensive industrial processes.

The study, "Ultrathin polymer membranes with locked intrinsic microporosity for hydrocarbon fractionation," has created a new way to form the separating layers in polymer membranes for molecular separations. The breakthrough derives from the way the cross-linking agent for the polymer film is added to the polymer during membrane fabrication.

It results in a scalable membrane technology capable of separating complex organic mixtures into valuable fractions with unprecedented efficiency. The membranes combine extremely high molecular selectivity with fast liquid transport—a combination that has long eluded scientists and engineers working in this field.

Conventional crude oil refining relies on thermal distillation, a process that consumes vast amounts of energy and accounts for around 1% of global energy use. Although membrane technologies have long promised a far more energy-efficient alternative, their industrial uptake has been limited by fundamental materials challenges.

"Membranes can, in principle, do the same job as distillation or evaporation, using far less energy," explains lead researcher Andrew Livingston, professor of chemical engineering and vice president of research and innovation at Queen Mary University of London, and CEO of Exactmer.

"The problem has been finding materials that are both fast and selective when exposed to real hydrocarbon mixtures."

The breakthrough reported in this study lies in a new way of manufacturing polymer membranes so that their nanoscale pores are "locked" in place during formation.

The researchers focused on polymers of intrinsic microporosity, materials known for their sponge-like structure containing sub-nanometer pores. While these pores are ideal for separating molecules by size and type, the polymers normally swell when exposed to hydrocarbons, causing the pores to expand and lose selectivity.

To overcome this, the team developed an in-situ cross-linking approach that stabilizes the polymer structure while the membrane is being formed. This process locks the pores in their optimal configuration, producing what the researchers call polymers of locked intrinsic microporosity (PLIMs).

"The key was stabilizing the structure before the polymer had a chance to swell," explains Dr. Zhiwei Jiang, who led the research as head of membrane research at Exactmer and who is now assistant professor at Nanyang Technological University in Singapore.

"This preserves the tiny pores that make molecular separation possible, while still allowing hydrocarbons to flow through very quickly."

To probe the molecular origins of locking, the UCL team, led by Dr. Foglia, used quasi-elastic neutron scattering at the ISIS Neutron and Muon Source, the U.K.'s national pulsed neutron facility and an unrivaled tool for studying polymer chain dynamics.

When tested with synthetic crude oil, PLIM membranes showed up to 10-fold higher permeance than existing state-of-the-art membranes while maintaining high selectivity. The membranes were able to discriminate effectively between hydrocarbon molecules that differ only slightly in size.

In tests using real Arabian Extra Light crude oil, the membranes:

The membranes also performed particularly well with refinery streams such as virgin naphtha. In these tests, they efficiently separated light hydrocarbons (C4–C6), suitable for fuel upgrading, from heavier naphtha fractions used to produce plastics and chemicals—all at permeances comparable to commercial desalination membranes.

Crucially, the researchers demonstrated that the membranes can be manufactured at scale. Using roll-to-roll processing, they produced sheets more than a meter wide and integrated them into standard spiral-wound membrane modules commonly used in industry.

"These membranes aren't just laboratory curiosities," said Dr. Adam Oxley, first author of the research paper and now deputy vice president of membranes at Exactmer. "They can be produced using established manufacturing techniques and fitted into existing industrial module designs. At Exactmer, we are building these new techniques into membranes used for high-value separations in organic solvents."

Long-term testing showed stable performance over 30 days of continuous operation, indicating strong potential for real industrial deployment.

While the global energy system is transitioning toward lower-carbon alternatives, demand r