New York | Researchers have developed a more efficient way of converting ethanol to a better alternative fuel without creating unwanted byproducts. Ethanol, which is produced from corn, is commonly used as an additive in engine fuel as a way to reduce harmful emissions.
However, since ethanol is an oxygenated fuel, its use results in a lower energy output, as well as increased damage to engines via corrosion. Researchers, led by William Jones at the University of Rochester in US, have developed a series of reactions that results in the selective conversion of ethanol to butanol, without producing unwanted byproducts.
Butanol is much better than ethanol as an alternative to gasoline. It yields more energy, is less volatile, and doesn’t cause damage to engines, said Jones. In fact, Jones was able to increase the amount of ethanol converted to butanol by almost 25 per cent over currently used methods.
Converting ethanol to butanol involves creating a larger chemical molecule with more carbon and hydrogen atoms. Although both molecules have a single oxygen atom, the higher carbon to oxygen ratio in butanol gives it a higher energy content, while the larger size make it less volatile. One method of converting the ethanol to butanol is the three step Guerbet reaction, which involves temporarily giving up hydrogen atoms in an intermediate step, then adding them back in to create the final product.
One problem with the Guerbet reaction is that an intermediate product acetaldehyde can react with both itself and the butanol product to create unwanted molecules. Jones modified the Guerbet reaction by using iridium as the initial catalyst and nickel or copper hydroxide, instead of potassium hydroxide, in the second step.
While the best current conditions for the Guerbet reaction convert ethanol to butanol with about 80 per cent selectivity, Jones’ reaction produced butanol in more than 99 per cent selectivity. No undesirable side products are produced. There’s still more work to do.
We’d like to have a catalyst that’s less expensive than iridium, said Jones. Also, we want to make the conversion process last longer, which means figuring out what currently makes it stop, he said. The process currently terminates after one day because one or more of the substances the iridium, nickel, and copper has broken down. Once we solve the remaining problems, we may be able to start looking for ways to apply the conversion process in the making of renewable fuels, said Jones.
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