Water-tolerant Catalyst Can Convert into Biofuel

Isobutanol is an ideal gasoline replacement due to its high energy density, suitable octane number and compatibility with engines. It can be formed by the Guerbet reaction in which ethanol and methanol mixtures are converted to this isobutanol in the presence of a suitable catalyst. However, the catalyst's water tolerance could limit the conversion as water is a by-product of the Guerbet reaction.

In their study, University of Bristol's Katy J. Pellow presents isobutanol formation using pre-catalyst trans-[RuCl₂(dppm)₂], which is shown to be tolerant to water in the system. Using the catalyst, the team achieved an isobutanol yield of 36% at 78% selectivity with water concentrations typical of that of a crude fermentation broth. Analysis revealed that the key to this success was the catalyst's tolerance to water itself, as well as the use of a hydroxide rather than an alkoxide base.

Alcoholic drinks can also be used as substitutes for the fermentation broth. The use of lager as the ethanol source yielded 29% isobutanol at 85% selectivity in the liquid phase.