Catalytic hydroprocessing of waste cooking oil for the production of drop-in aviation fuel and optimization for improving jet biofuel quality in a fixed bed reactor

Abstract

Waste cooking oil (WCO) is a bio-waste with significant potential for developing improved transportation fuel, specifically for the aviation industry. This work investigates the catalytic hydrocracking of WCO over commercial hydrocracking catalyst (Ni-Mo/silica-alumina) in a continuous flow fixed bed reactor to produce jet range hydrocarbons (HCs). The aim was to convert WCO into sustainable aviation and automotive fuel to get the maximum benefit from waste oil with high selectivity towards paraffins, naphthenes, minimal aromatics, and high isomerization (isomer to normal (i/n) ratio) in a single-step process using a single catalyst composition. The higher i/n ratio boosts specific energy, thermal stability and provides a low freezing point to the fuel. The results show that WCO conversion of 96.6 % with 55.6 % selectivity of jet range HCs was obtained at 420 °C temperature, 1 h−1 LHSV, 10 MPa pressure, and 2200 NLgas/Lliquid H2/oil ratio. In addition, isomer yield of 82.9 %, i/n ratio of 4.8, and selectivity of kerosene range HCs based on paraffins (43.6 %), naphthenes (8.2 %), and aromatics (3.73 %) was obtained at optimum reaction conditions. After hydroprocessing, the major fraction of heteroatoms (N = 99.9 %, S = 94.3 %, O = 99.9 %) was removed from WCO. Finally, the time on stream (TOS) study showed no deactivation of the catalyst up to 590 h, indicating the long life and stability of the catalyst, which is one of the highest lifetimes reported so far. Bio-jet fuel properties were tested according to the ASTM D-1655 standard. This research will aid in developing novel catalysts for the selective conversion of WCO into jet range HCs in a single step process.