The conversion of coconut oil into hydrocarbons within the chain length range of jet fuel

The present work concerns the conversion of coconut oil into hydrocarbons within the chain length range of jet biofuel through the pathway called hydroprocessing of esters and fatty acids (HEFA). The aim is to employ the resulting mixture as an alternative biofuel in the aviation sector. The process involved two steps: (i) hydrodeoxygenation (HDO) over a sulfided NiMo/Al2O3 catalyst, followed by (ii) hydroisomerization (HIS) over a Pt/SAPO-11 catalyst. Preliminary tests were carried out with model compounds: lauric acid and n-dodecane for HDO and HIS, respectively. In both steps, middle processing temperatures (~ 340–350 °C) were low enough to prevent excessive cracking but high enough to provide acceptable reaction rates and to prevent coke formation. The HDO step rendered a mixture constituted basically by n-alkanes. The subsequent HIS permitted to increase the content of branched chains. The final HEFA-SPK (where SPK is the abbreviation for synthetic paraffinic kerosene) had an acidic index zero and a relatively high content of monomethylalkanes. Furthermore, due to the fatty chain composition of the starting oil, the chain length distribution of the resulting biofuel matched well with that of conventional jet fuels, so that subsequent steps of cracking and fractionation, which increase costs and reduce the process yield, were not required. The obtained results are encouraging in terms of using coconut oil-based HEFA-SPK in the formulation of sustainable alternative jet fuels at competitive costs and with relevant environmental and social benefits.