Scientists led by a team at Caltech have developed a new method for potentially removing nearly all sulfur compounds from gas and diesel fuel.
Sulfur compounds in fuels such as gasoline and diesel create air pollution when the fuel is burned. To address that challenge, large-scale oil refinery processes remove the majority of sulfur from fuel down to a government-mandated level. The new technique, however, has the potential to reduce sulfur down to a fraction of that amount, which would further reduce air pollution and extend the lifetime of vehicles’ catalytic converters, which control tailpipe emissions.
The results—from a team led by Caltech and BP, and in collaboration with researchers at UCLA, ETH Zürich, and China’s Nanjing University—are described in a new study published online February 17 in the journal Nature Energy.
The ability to reduce sulfur in fuels is an important step toward reducing emissions. However, extremely low levels can be difficult to achieve. Now, Caltech researchers have demonstrated an unorthodox approach that lowers sulfur content in diesel to about 2 ppm. The method uses Earth-abundant materials (potassium (K), oxygen (O), and silicon (Si)—hence the name, “KOSi“) and operates under mild conditions.
“We simulated a high-sulfur oil and eliminated almost all of the sulfur through a simple chemical process. The next step is figuring out how to streamline the process and make it work on an industrial scale,” says lead author Anton Toutov, a graduate student in the lab of Robert Grubbs, the Victor and Elizabeth Atkins Professor of Chemistry at Caltech.
The new method uses a potassium salt to induce the chemical reactions required to remove sulfur from fuel. Potassium is an abundant element on Earth and cheaper and more environmentally friendly to use than rare metal catalysts that are used for similar reactions.
The new method could be used as an additional step in the oil refinement process to get rid of the last traces of sulfur in fuels. The next step for Toutov, who is co-founding a new company, Fuzionaire, is to commercialize this technology. “We have a number of ideas in mind on how to do that,” he says, including recycling waste products from other industries for use in the process.