From Sugarcane To Jet Fuel

A California-based research team has shown that chemical building blocks derived from sugarcane can be converted in nearly 100% yield to a new family of potentially high-performing jet fuels. An environmental impact analysis of the biobased strategy suggests that it would lead to a reduction of up to 80% in greenhouse gas emissions, compared with an approach that makes the same compounds from petroleum (Proc. Natl. Acad. Sci. USA 2015, DOI: 10.1073/pnas.1508274112).

To reduce global dependence on petroleum and mitigate the harmful effects of climate change, numerous research groups have developed methods for producing biobased car and truck fuels and various types of chemicals. Stringent specifications for aviation fuels, however, have limited researchers’ success in producing those products from biological sources.

For example, aviation fuels need to be formulated from oxygen-free compounds that yield high-energy-density blends with low freezing points and low viscosity values. Those high-altitude requirements are best met with branched and cyclic hydrocarbons, which are not easy to produce from current biobased methods: Some of these approaches to making jet fuels give low yields or are energy intensive.

A new synthesis strategy developed by University of California, Berkeley, scientists Alexis T. Bell, Corinne D. Scown, F. Dean Toste, and coworkers can overcome these obstacles. The team demonstrated that condensing alkyl methyl ketones derived from Brazilian sugarcane, followed by deoxygenation, leads to high-yield cyclic products in the C₁₂‒C₄₅ range that can serve as jet fuels (C₁₂‒C₂₁) as well as automotive lubricants (C₃₃₊).

The energy density of the jet fuel compounds exceeds that of conventional jet fuels. And the compounds’ freezing points, cold-flow characteristics, and other viscosity-related properties are superior to those of biobased jet fuels made via other methods. The lubricants’ viscosity-related properties are comparable to high-quality synthetic automotive lubricants, far exceeding those of standard petroleum oils.

Xinhe Bao, a catalysis research group leader at China’s Dalian Institute of Chemical Physics, remarks that the study provides “a viable strategy for sustainable production of jet fuels and lubricant oils in a sugarcane refinery.” He adds that the synthesis strategy, which is based on inexpensive, recyclable catalysts, leads to a substantial reduction in the emissions of greenhouse gases.

The University of Wisconsin’s James A. Dumesic, a biomass conversion specialist, notes that not only is the process efficient, but it’s also industrially scalable. He adds: “This work offers important guidelines to scientists for future research, as well as insight to policy-makers.”