Bio-hydrocarbons through catalytic pyrolysis of used cooking oils and fatty acids for sustainable jet and road fuel production

Used Cooking Oil (UCO) and pure Fatty Acids (FAs) derived from food processing represent sustainable feedstocks for biofuel production. The catalytic and non-catalytic pyrolysis of these residual oils is a possible pathway to advanced biofuel production, alternative to catalytic hydrotreatment, already commercially deployed in large-scale installations. The present work first carried out a literature review of previous research works in the field, which provided the key information to the following implementation of a pilot-scale dedicated experimental work aimed at producing bio-hydrocarbons from residual vegetable oils, with a special focus on paraffinic fuels. Based on the literature survey, 4 different catalysts were selected for the experimental investigation. Catalytic and non-catalytic pyrolysis of UCO was initially carried out in 1.5 kg h−1 (max) feed pilot unit, operated at 500 °C, with the catalytic reactor working at 4 and 2.5 h−1 Weight Hourly Space Velocity (WHSV). Liquid yields and corresponding hydrocarbon fractions were investigated: these initial results suggested to extend the study to catalytic pyrolysis of pure FAs. At T = 500 °C and with activated carbons as catalyst, the total observed hydrocarbon yield mass fraction on UCO and FA increased from 23% (UWHSV = 4 h−1) to 35% (UCO, WHSV = 2.5 h−1) and finally to 40% (FA, WHSV = 2.5 h−1). A slight reduction in the overall liquid yield mass fraction was also observed in this last experiment with FAs (from 63% to ≈49%). Even if the current work on the pilot pyrolyser did not aim at investigating energy and process optimization, including yield maximization and catalyst lifetime, experimental results indicated that catalytic pyrolysis could be a promising way for industrial production of hydrocarbons from low quality lipid-based materials (as it is the case of UCOs) and without requiring hydrogen for catalytic hydrotreatment.