Due to the fast depletion of fossil fuels and the aggravation of environmental problems, it is urgent to develop renewable and clean energies to substitute the traditional fossil fuels. Biomass, a traditional renewable energy that has been developed for centuries, is an ideal material for producing liquid transportation fuels because the biomass contains abundant C and H element. Typical biomass resources such as plant oils and animal fats possess abundant fatty acids with similar hydrocarbon chains with the diesel, thus can serve as the renewable liquid fuel feedstock for producing the aviation fuels. Deoxygenation of the fatty acids to produce alkanes is a promising method to convert the biomass into chemical fuels. However, gaseous hydrogen is generally required in the process, which brings H2 production, storage, transportation and related safety issues. Our previous research has shown that the in situ formed hydrogen from the reaction of high-temperature water (HTW) with earth-abundant metals (Fe, Zn, Al etc.) is more effective for reduction reactions than the gaseous H2. Thus, if this method can be applied for the fatty acid deoxygenation, a one-step hydrogen production and highly-efficient fatty acids deoxygenation for alkanes production to mitigate the problem of fossil fuel depletion can be achieved. Results showed that the fatty acids could be hardly converted to alkanes without any catalyst. However, interestingly, when a normal Ni was used as the catalyst, a 90% yield of pentadecane was successfully obtained from the deoxygenation of palmitic acid at 300 oC for 16 h with Zn as the re-generable reductant. Furthermore, the Ni catalyst was stable for the fatty acid deoxygenation after several recycles. We also investigated the conversion of other fatty acids such as lauric acid and stearic acid into related alkanes with this method. Results showed that the alkane yields were over 80% for the tested fatty acids. Detailed studies revealed that the in situ formed H2 provided a high reduction atmosphere, which helps the Ni catalyst maintain a fresh Ni0 surface and then probably results in the high catalytic activity of the Ni catalyst. Based on these results, this research proposed a green, simple and highly efficient process for producing aviation fuel from biomass with a simple and stable catalyst, which is the key for the practical application.

Deoxygenation of fatty acids to alkanes in water with Ni catalyst

256th National Meeting (2018)

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