A new membrane could reduce reliance on energy-intensive distillation for selected crude oil separation steps.

How does KAUST’s new membrane help with crude oil separation?

Crude oil is a complex mixture of compounds called hydrocarbons, made up of hydrogen and carbon atoms. For more than a century, refineries have relied on distillation to separate this mixture. By heating the oil, components with different boiling points can be collected separately.

However, this approach is energy-intensive and struggles to separate hydrocarbons with similar boiling points but different chemical structures.

In a study published in Science, a KAUST-led team has developed a membrane that tackles this challenge differently. Its tiny pores and carefully tailored chemistry favor the passage of certain hydrocarbons over others.

How does the membrane select which molecules pass through?

The membrane is made from a covalent organic framework (COF): a crystalline material whose molecular building blocks form an ordered structure containing precisely defined pores.

The researchers adjusted the COF’s layers and added chemical groups inside its pores, creating openings that favored aliphatic over aromatic hydrocarbons. Although these groups can have similar boiling points, the different arrangements of their carbon and hydrogen atoms give them distinct chemical properties.

The membrane exploits these differences to separate the hydrocarbons more efficiently. It combines molecular sieving, which controls which molecules pass through tiny pores, with chemical interactions that help separate the two groups.

In tests with Arabian Light crude oil, aliphatic hydrocarbons made up 54.5% of the original oil mixture. After passing the oil through the membrane once, aliphatics accounted for 92.0% of the collected liquid. A second membrane stage increased this proportion to 96.1%. Membranes measuring 50 meters long and 0.3 meters wide operated stably for more than two months.

“A membrane that works on a small laboratory sample is only part of the challenge,” says Li Cao, researcher who led the study. “We also need to manufacture it consistently and show that it can work in practical equipment. Our results bring those requirements together.”

Read more at KAUST Discovery.