New catalysts convert ethanol to butanol with high selectivity; potential low-cost upgrade for ethanol plants
Researchers at the University of Bristol (UK) have developed a new family of catalysts that enables the conversion of ethanol into n-butanol—a higher alcohol with better characteristics for transportation applications than ethanol—with selectivity of more than 95% at good conversion. The team presented a pair of papers on their work at the Spring meeting of the American Chemical Society this week in New Orleans.
While butanol has emerged as a potential sustainable liquid fuel replacement for gasoline, development of biosynthetic pathways for its synthesis are challenged by very low conversion and modest selectivity, they noted. Although catalytically upgrading the more readily available bioethanol to butanol is theoretically attractive, this has been hampered by modest selectivity in most cases.
The Bristol team developed homogeneous ruthenium diphosphine catalysts for the upgrade of ethanol to butanol. At the ACS meeting, they presented results from a preliminary mechanistic study into the new catalysts suggesting that high selectivity is achieved because the catalyst imparts control over acetaldehyde aldol condensation reactions, with evidence for an on-metal condensation step.
These new catalysts are much better than any previously in existence. There’s a long way to go before they are commercialized, but we are reporting a fundamental advance in that direction. Quite simply, they are the world’s best catalysts for making the gasoline of the future.—Professor Duncan Wass
The new catalysts could reduce the costs of converting ethanol factories to production of butanol. Efforts already have begun to convert some ethanol factories in the Corn Belt to production of butanol, Wass explained, but converting those factories to ferment corn into butanol would require modifications estimated at $10 million-$15 million for a typical plant.
However, with the new catalysts, the ethanol produced in conventional facilities could simply be upgraded to butanol in an additional reaction step.
Wass’ team acknowledges funding from BP.
Duncan Wass, Rich Wingad, George Dowson, Jason Lee (2013) CATL 195 - Catalytic conversion of ethanol to an advanced biofuel: Unprecedented selectivity to n-butanol
Richard L Wingad, Duncan F Wass, George Dowson, Jason Lee (2013) CATL 197 - Catalytic conversion of ethanol to an advanced biofuel: Exploring ligand effects