Gasoline is a complex blend of different ingredients. One component that beefs up octane and cuts down on smog is called alkylate. It makes up about 10% of the gasoline consumed worldwide– that’s more than 13 billion gallons of alkylate per year for the U.S. alone.
Besides boosting octane, alkylate contains virtually no sulfur, so it burns cleaner than other fuels and it keeps gasoline from boiling off in the summer heat.
But making alkylate is hazardous, requiring lots of sulfuric or hydrofluoric acid. Besides being highly corrosive, these acids release poisonous fumes and can burn through skin. This makes them extremely dangerous to transport, store and handle.
Researchers at the Center for Environmentally Beneficial Catalysis, or CEBC, have found a potentially safer way to make this critical gasoline component.
“We are testing the use of acidic ionic liquids as potential replacements for mineral acids that current processes use,” said Bala Subramaniam, CEBC Director. Ionic liquids are carbon-based salts that are liquid near room temperature. Unlike conventional solvents, they don’t evaporate or emit toxic fumes into the air.
The researchers tested six different ionic liquids, either alone or mixed with the acids.
“We found that mixtures of ionic liquid and acid were better at making alkylate than the pure acids alone,” said Aaron Scurto, assistant professor of chemical engineering.
The mixtures release fewer poisonous fumes than the pure acids. They were also easier to separate from the final product than the pure acids, making it feasible to recycle the acid catalyst for reuse.
The findings have been published in the Journal of Catalysis . They could eventually lead to a safer method for making gasoline alkylate by reducing the use of toxic acids.
And, if the results hold up, ionic liquids might also be used in other chemical processes that require acid catalysts.
--Story by Claudia Bode
 Tang, S.; Scurto, A. M.; Subramaniam, B. “Improved 1-butene/isobutane alkylation with acidic ionic liquids and tunable acid/ionic liquid mixtures,” Journal of Catalysis 2009 268:2, pp 243-250.