Nanoparticles in Biofuel Production

Sankar Nair in the lab with a member of his research team.Fuel prices are at record highs and so is the demand for alternative fuels. But major scientific and technological advances are still required before economically viable alternative fuels become a significant part of the U.S. energy supply.

Researchers across the Georgia Institute of Technology campus, including numerous ChBE faculty members, are focusing their attention on biofuels. And while most experts agree that biofuels are not the silver bullet to solve the world’s long-term fuel needs, they see biofuels as a necessary complement to conventional oil and gas.

For bioethanol, once the sugars are fermented into alcohol, a significant amount of water must be separated out. This separation primarily occurs in a distillation column, which involves heating the mixture and separating the components by the differences in their boiling points.

Dr. William J. Koros (left)“Distillation is very energy intensive and expensive, and it might defeat the purpose when you’re trying to produce biofuel economically,” says Sankar Nair (left), an associate professor in the School of Chemical and Biomolecular Engineering, who is collaborating with William J. Koros (right), the Roberto C. Goizueta Chair for Excellence in Chemical Engineering and the GRA Eminent Scholar in Membranes, on two separation projects aimed at improving the energy efficiency of the biofuel process.

A membrane-based approach would avoid the need to supply heat energy, and instead rely on differences in the transport rates of the components through a membrane to achieve separation. The challenge is in producing selective membrane systems that can produce pure ethanol. Polymer materials have been widely investigated and have the advantage of high throughput, but such membranes can’t yet produce pure ethanol from a dilute ethanol-water mixture, notes Nair.

Instead, Nair and Koros are exploring membranes (like the one shown below) that contain nanoparticles of porous inorganic materials called zeolites that are so small they can be dispersed efficiently into a polymer matrix. The very specific porosity of the zeolite should allow separation of ethanol from water. By using two membranes in series – the first hydrophobic to remove ethanol from a large mass of water and the second hydrophilic to remove any trace water in the ethanol product from the first membrane – it may be possible to design an economical membrane process for biofuel separation from water.

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