Hydrothermal hydrogenation/deoxygenation of palmitic acid to alkanes over Ni/activated carbon catalyst

Abstract

To produce paraffin from hydrogenation/deoxygenation of palmitic acid, model compound of bio-oil obtained by hydrothermal liquefaction (HTL) of microalgae, has been an attractive focus in recent years. In order to avoid energy-intensive separation process of water and bio-oil, it is of importance that deoxygenation upgrading of fatty acids under hydrothermal conditions similar with HTL process. Herein, it is the first time to explore the application of activated carbon (AC) supported non-noble-metal catalysts such as Ni, Co, and Mo, etc., in the hydrothermal hydrogenation/deoxygenation of long-chain fatty acids, and the obtained Ni/AC–H (the Ni/AC was further H2 pre-reduced) is one of the best catalysts. In addition, it is found that the catalytic activity can be further improved by H2 pre-reduction of catalyst. Characterization results that more low valences of nickel and oxygen vacancy can be obtained after H2 pre-reduction, thus significant promoting the deoxygenation especially the decarbonylation pathway of fatty acids. The total alkanes yield can reaches 95.9% at optimal condition (280 °C, 360 min). This work confirmed that the low-priced AC supported non-noble-metal catalysts have great potential compared with the noble-metal catalyst, in hydrothermal upgrading of bio-oil.