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Oil is the backbone of modern society despite efforts to move towards renewable energy sources. It supplies fuels and chemicals for heating and transportation, from plastics to pharmaceuticals. But all these uses require the separation of crude oil into its various components. That separation process—typically heat-based—takes enormous amounts of energy and accounts for about 1% of global greenhouse gas emissions each year.
Now, chemists say a newly developed material could one day reduce this significant — if mostly invisible — carbon footprint by 230 gigawatts a year, equivalent to Nevada’s entire energy consumption. Researchers reported this week that a novel coating could more than halve the energy needed to separate crude oil if expanded. Such a coating would not only make crude oil greener, but it would also be cheaper for refineries to produce, saving billions of dollars a year in energy costs.
“The savings potential is amazing,” said Ryan Lively, a chemical engineer at the Georgia Institute of Technology who was not involved in the new work. The new coatings should last for months, if not years, he said. He and other conventional refiners warn that they may be slow to adopt them because companies have already cut costs by deploying conventional separation systems. But, Lively said, the new membranes could quickly be adopted in new filters built to separate hydrocarbon compounds created from biofuels or fossil fuels. “That’s really ripe territory,” Lively said.
Crude oil is a mixture of tens of thousands of chemicals. The first step in petroleum refining is to separate that mixture through the distillation process. The raw crude oil is heated up to 500 °C. Lighter components such as gasoline vaporize and condense at lower temperatures. Heavy components such as home heating oil evaporate at higher temperatures.
Two years ago, researchers led by Lively and chemical engineer Andrew Livingstone of Queen Mary University of London in Science Instead of filtering, it was possible to separate these parts by using membranes. They created membranes with built-in pores that allowed small, light hydrocarbons to pass through and larger, heavier ones to escape. But lighter hydrocarbons pass through the layers too slowly to be of real-world use.
To get around this, Livingston and his colleagues turned to an industrial approach to ultrathin water-repellent coatings called interfacial polymerization. They hoped that thin layers would allow the required hydrocarbons to pass through more quickly. However, Livingstone notes, while conventional desalination coatings are strong in a water-based environment, they fail quickly when hydrocarbons containing industrial solvents are introduced.
Therefore, he and his colleagues developed polymers that contain conventional membranes. First, they made single polymers by connecting a hydrophobic or oil-like segment with a hydrophilic or water-like strand. When you add these molecules to a mixture of oil and water, they suddenly assemble into small bubbles or vesicles, with the hydrophobic part facing inside. They then use the interfacial polymerization technique to distribute these vesicles into a continuous ultrathin sheet and bond all the polymers together to form a solid coating.
The approach worked. The vessel’s hydrophobic cores allow selected (based on size and other properties) hydrocarbons to pass through more easily — 10 times faster than previous oil-separation membranes, Livingston and colleagues reported yesterday. Science. The researchers also showed that by tailoring the chemistry of the polymers, they can create different membranes that selectively pass through different amounts of hydrocarbons.
According to Neal Rannekar, a chemical engineer with Exxon and a team member on the new paper, switching from distillation to membrane separation could save up to 50% of the crude oil used for heating and 75% of the electricity used to refine it. It amounts to at least $3.5 billion a year.
“It’s a very interesting result,” said David Scholl, a dissociation expert at Oak Ridge National Laboratory who was not involved in the study. However, Sholl notes, the novel coatings are not yet ready for industrial use. They still need to scale up to a hundred square meters of paper size and keep it in continuous use for months. But Scholl says these encouraging findings confirm that oil companies will continue to explore technology to save money and reduce carbon emissions. “All the chemical companies are very interested in doing this,” he said.
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