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China researchers develop new pathway for jet-range bio-cycloalkanes from acetone and hydrogen

Researchers from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, have developed a new route for the synthesis of jet-fuel range C10 and C12 cycloalkanes using diacetone alcohol (the self-aldol condensation product of acetone under mild conditions)—which can be derived from lignocellulosic biomass—and hydrogen. A paper on their work is published in the RSC journal Green Chemistry.

The branched cycloalkanes are synthesized with high carbon yield (~76%), have high density (0.83 g mL-1) and a low freezing point (216.5 K). As a potential application, they can be used as additives to conventional bio-jet fuel comprising C8-C16 chain alkanes.

During the past years, the synthesis of jet fuel range hydrocarbons with the lignocellulose-derived platform compounds has drawn a lot of attention. So far, most of the reported work about lignocellulosic bio-jet fuel was concentrated on the synthesis of C8-C16 chain alkanes. These alkanes have relatively lower densities (~0.76 g mL-1 vs. ~0.81 g mL-1) or volumetric heating values than that of conventional jet fuel (a mixture of chain alkanes and cyclic hydrocarbons). In real application, they must be blended with conventional jet fuel to meet the specification of aviation fuel.

Compared with chain alkanes, cyclic hydrocarbons have relatively higher densities or volumetric heating values due to strong ring strain. As a solution to the shortage of conventional bio-jet fuel at lower density, it is still necessary to develop some new routes for the synthesis of jet fuel range cyclic hydrocarbons with lignocellulosic platform compounds.

Acetone is the by-product of bio-butanol from the Acetone-Butanol-Ethanol (ABE) fermentation of lignocellulose. In a typical ABE fermentation, butanol, acetone and ethanol are produced at a weight ratio of 6:3:1. With the large-scale application of bio-butanol as the substitute of gasoline or the feedstock in the production of bio-diesel and bio-jet fuel, the exploration of big outlets for acetone (e.g. transportation fuel) is attracting more and more attention. … To the best of our knowledge, there is no report about the production of jet fuel range alkane with diacetone alcohol as the feedstock. In this work, a new route for the synthesis of jet fuel range C10 and C12 cycloalkanes with diacetone alcohol and hydrogen was first developed.

—Chen et al.

Chen
Strategy for the synthesis of jet fuel range cycloalkanes with diacetone alcohol which can be derived from lignocellulose. Chen et al. Click to enlarge.

The new synthetic route has three steps:

  • Diacetone alcohol was hydrogenated to 2-methyl-2,4-pentanediol. Among the investigated catalysts, Ru/C had the highest activity for this reaction.

  • 2-methyl-2,4-pentanediol was converted to C10 and C12 cycloalkenes by dehydration/Diels Alder reaction over acidic catalysts. Nafion resin exhibited the highest activity among the investigated catalysts.

  • The C10 and C12 cycloalkenes obtained in the second step were further hydrogenated to C10 and C12 cycloalkanes with a high density (0.83 g mL-1).

This work opens a new strategy for the synthesis of jet fuel range cycloalkanes with lignocellulosic platform compound.

—Chen et al.

Resources

  • Fang Chen, Ning Li, Shanshan Li, Guangyi Li, Ai-Qin Wang, Yu Cong, Xiaodong Wang and Tao Zhang (2016) “Synthesis of jet fuel range cycloalkanes with diacetone alcohol from lignocellulose” Green Chem. doi: 10.1039/C6GC01497F

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