Catalytic hydrocracking of inedible palm stearin for the production of drop-in aviation fuel and comparison with other inedible oils

Abstract

This work describes the use of palm stearin oil as a feed for the catalytic hydrocracking to produce the renewable aviation kerosene and diesel using the hydrocracking catalyst in a continuous flow fixed bed reactor. The efficacy of this method is evaluated using several reaction parameters, including hydrocracking temperature, hydrogen pressure, liquid hourly space velocity (LHSV), hydrogen to feed ratio (H2/feed) and time on stream (TOS). Higher temperatures and lower LHSVs are dominant to produce kerosene with maximum selectivity of 55.7%, while lower temperatures and LHSVs favoured the diesel production with maximum of 75.4% selectivity. The isomerization reactions were promoted by higher hydrocracking temperature due to the increase in iso-paraffins. The products consist of paraffins (96.9–99.3%), naphthenes (0.1–1.86%) and aromatics (0.2–1.59%). Aromatization reactions were also taking place in the process which is a considerable benefit of this method as aromatization reactions decrease hydrogen consumption. Moderate hydrogen pressure and H2/feed ratio favour the kerosene yield. The reaction mechanistic pathway was also proposed for converting palm stearin to biofuels. Furthermore, product yield, selectivity, heteroatom removal, and double bond saturation were also explored. The stability and activity of the catalyst were studied for 600 h without observable deactivation of the catalyst.