Smart membranes separate oil

Around 90 million barrels of crude oil are processed worldwide every day, mostly by heating the oil up to 400 °C to separate it into fractions based on different boiling points. This consumes as much energy, globally, as the total consumption of a country such as the United Kingdom.

“The aim of our research is to provide low energy alternatives,” says Andrew Livingston, of Queen Mary University London, leader of the international research team. He says the work benefitted greatly from the assistance of researchers at KAUST led by “world-leading” membrane scientist, Suzana Nunes.

The innovation is based on ultra-thin films composed of polyamide molecules that can be designed to let small organic molecules of crude oil pass through while blocking larger ones. The polyamide forms when individual monomer molecules join together. Importantly, it must be sufficiently robust to withstand the pressures needed to push the separated molecules through.

“We were amazed to see that little balls of monomer that formed in solution turned up in the final films as half spheres that I was sure would be a weak point, but amazingly they could take high pressure without deforming,” Livingston says.

A key challenge was to create robust thin films that possess hydrophobicity, meaning they have a high affinity for the hydrocarbons in crude oil. By achieving appropriate hydrophobicity, the team made films that can separate liquid factions of crude oil 100 times faster than existing non-hydrophobic (hydrophilic) membranes and ten times faster than the current hydrophobic ones.

Membrane specialist, Zhongyi Jiang, at Tianjin University in China, who was not involved in the work, comments: “This is an ingenious design at the molecular level…. I believe it will transform both the membrane community and the petrochemical industry, using ultrathin hydrophobic membranes towards greener and sustainable hydrocarbon separations."

“We now need to scale the membranes up from A4 sheets to 100-metre rolls,” says Livingston. “This is challenging, but we are optimistic.”

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