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Abstract Conversion of biomass and waste oils to alkanes for the production of aviation fuel is attracting increasing research interests since it can provide sustainable energies from renewable resources to substitute the fossil fuels. In this process, the deoxygenation of fatty acids to alkanes is the key reaction. However, previous methods of fatty acids deoxygenation require gaseous hydrogen, noble metal catalyst and/or organic solvent, which are adverse to the sustainable development. In this work, a novel and simple method of deoxygenation of fatty acids to alkanes is proposed by using a commercial nickel (Ni) powder as the catalyst without any pre-treatment and water as both environmental-friendly solvent and sustainable hydrogen source. The hydrogen in situ generated from water exhibited a much higher activity than gaseous hydrogen for the deoxygenation of fatty acids, and an alkane yield of 90% was successfully achieved. The Ni catalyst is stable and still maintains high activity after recycles. This proposed process is simple, economical, sustainable and environmental-friendly, thus is promising for the practical application. Graphical abstract Image 1 Highlights • A highly-efficient way to deoxygenation of fatty acids with hydrogen from water. • Requires neither noble metal catalysts nor gaseous hydrogen. • Water acts as both reaction medium and hydrogen source for fatty acids deoxygenation. • Non-precious Ni catalyst shows excellent activity and stability. • In situ formed H 2 exhibits high activity for the fatty acids deoxygenation. [ABSTRACT FROM AUTHOR]

In this paper, we give an overview of recent advances in the production of formic acid, as a hydrogen carrier, from CO 2 and water by using the earth-abundant metal of Fe as the reductant under hydrothermal conditions, which mainly includes: 1) hydrogen production from water with Fe; 2) reduction of HCO 3 – to formic acid in the presence and absence of catalysts; 3) proposed reaction mechanisms. The novel options under this study are mainly the use of water as a hydrogen source with metal Fe as a reductant, and the formed Fe x O y as an auto-catalyst. Such a process possesses several benefits: (i) water acts not only as a hydrogen source but also as an environmentally benign solvent; (ii) there are no hydrogen requirements, including pumps or storage, because hydrogen is derived from water and reacts with CO 2 in situ ; (iii) no exotic catalysts or harsh reagents are used; and (iv) the method is simple and highly efficient. This technology can provide a one-step, sustainable and highly efficient way to reduce CO 2 into formic acid using the hydrogen directly from water. [ABSTRACT FROM AUTHOR]