Ultrathin membranes could transform hydrocarbon processing by slashing energy use - Engineering - Energy & Green Tech

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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.

The work is published in the journal Science.

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.

Re-thinking a century-old process

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."

Locking pores at the nanoscale

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.

Exceptional performance in crude oil and refinery streams

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:

• Removed 99.8% of hydrocarbons heavier than 15 carbon atoms
• Reduced sulfur-containing compounds by 93%, a critical step in protecting downstream catalysts and equipment

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.

Designed for scale-up

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.

A more sustainable pathway for refining

While the global energy system is transitioning toward lower-carbon alternatives, demand remains for fuels, chemicals, solvents and materials derived from hydrocarbons. Improving the efficiency of existing separation processes is therefore essential to reducing emissions during the transition period.

By enabling membrane-based separations that are both fast and selective, the PLIM technology could allow industries from oil refining to pharmaceuticals to:

• Cut energy consumption dramatically
• Reduce carbon emissions
• Operate with smaller, more flexible processing units
• Integrate selective desulfurization earlier in the refining process

The researchers note that the same pore-locking concept could be extended to other liquid separation challenges, including chemical manufacturing, solvent recovery and emerging bio-based feedstocks.

Looking ahead

The team is now exploring greener solvents for membrane manufacture and investigating how PLIM membranes could be deployed in targeted hybrid processes alongside existing refinery infrastructure and the manufacture of high-value pharmaceuticals in organic solvents.

"This work shows that membrane-based molecular separation in organic liquids is no longer just a theoretical possibility," said Livingston. "With the right materials design, it can be fast, selective, scalable—and ready for industry."

Dr. Zachary P. Smith, associate professor of chemical engineering, Massachusetts Institute of Technology (MIT), said, "As all chemists know, 'like dissolves like.' So how can you separate hydrocarbon liquids using a hydrocarbon polymer without the polymer itself dissolving while in use? Livingston and his team have developed an approach to 'lock' their polymers in place, making them stable under aggressive conditions.

"More than that, they have shown that this approach works with some of the newest and most innovative emerging polymers in membrane science, helping to push the field into untapped areas of application."

Ryan P. Lively, professor in the School of Chemical & Biomolecular Engineering at the Georgia Institute of Technology, added,

"One of the key technological barriers facing membrane deployment in crude oil refining [is/was] the very low productivity of the membrane units. The membranes from Livingston's research are more than 100 times more productive than the first-generation membrane materials—the fact that this was achieved along with improved separation efficiency is a remarkable achievement.

"The composition of the membrane selective layer is interesting. The polymer backbones used had been considered previously, and cross-linked polymers had been considered previously, but the special combination that the team discovered really hit a sweet spot in terms of membrane performance.

"Being able to go from a small postage-stamp test to a full-size membrane module in such a short time indicates that the prospects for membrane-based oil refining are bright. Indeed, this article and others in the academic literature continue to indicate that there are real economic and environmental benefits to moving forward with membranes for oil refining at larger and larger scales." 

Provided by Queen Mary, University of London 

by Queen Mary, University of London

edited by Sadie Harley, reviewed by Robert Egan 

Source: Ultrathin membranes could transform hydrocarbon processing by slashing energy use