Hydrothermal stable Ni nanoparticles encapsulated in carbon for hydrothermal hydrogenation of long-chain fatty acids to alkanes

Abstract

Upgrading bio-oil to hydrocarbon fuels has been a research focus in the field of renewable energy. However, preparing catalysts with high activity, low cost, and high hydrothermal stability poses enormous challenges. In this work, nickel nanoparticles (Ni NPs) encapsulated in carbon are synthesized with an extremely simple scheme and used to catalyze palmitic acid to alkanes through a one-pot method in aqueous phase. The Ni0.5@C0.5 catalyst is highly efficient at achieving full conversion from palmitic acid at 280 °C within 120 min, and the yield of alkanes reached up to 97.9% and exhibited superior hydrothermal stability. Research results indicate that highly dispersed Ni0 is the active site of the catalyst. The coating structure with a graphitic layer provides the guarantee of hydrothermal stability of the catalyst. Firstly, the carbon layer can effectively avoid direct exposure of metal to high-temperature water, and inhibit metal leaching. In addition, the internal carbon layer separates and disperses Ni NPs and inhibits aggregation. Moreover, the Ni0.5@C0.5 catalyst is suitable for the hydrothermal hydrogenation of various fatty acids/methyl esters. This work provides a new strategy for obtaining catalysts with excellent hydrothermal stability and improving the catalytic activity of bio-oil deoxygenation.