Researchers at the U.S. Naval Air Warfare Center, China Lake have synthesized a new class of renewable diesel fuels from a methyl ketone and diols including 2,3-butanediol, 1,2-propanediol, and ethylene glycol. These fuels exhibit comparable net heats of combustion (NHOCs) to conventional biodiesel, while maintaining derived cetane numbers between 82-91. These values are 20–30 units higher than conventional biodiesel and 40–50 units higher than petroleum-derived diesel fuel.
The short combustion delays of the new fuels make them compelling blendstocks to enhance the combustion efficiency of petroleum-derived diesel fuel; further, careful selection of the renewable diol allows for custom tailoring of viscosity and freezing point. In addition, methyl ketones can be efficiently generated from sugar feedstocks or CO2/H2 with metabolically engineered microorganisms, while the diols can be readily obtained from biomass sugars via fermentation or chemical methods.
In a paper in the RSC journal Sustainable Energy & Fuels, the team suggests that this biosynthetic approach may allow for the generation of these fuels on industrially relevant scales while eliminating competition with food sources and promoting responsible use of land resources.
The researchers synthesized three dioxolane compounds using equimolar amounts of a given diol and 2-tridecanone and a low-cost acid catalyst. After establishing the purity of the dioxolanes, the team measured the key fuel properties, including densities, net heats of combustion (NHOC), viscosities, freezing/melting points, and derived cetane numbers (DCN).
In their paper, the researchers note that use of lignocellulosic biomass as a feedstock could enable large-scale production of these fuels with concomitant significant reductions in greenhouse gas emissions and the potential for eventual cost parity with petroleum-derived fuels.
