LAUSR

Abstract In this work, the thermal catalytic cracking of waste chicken fat on a coal fly ash catalyst was investigated. The objectives were to find the optimizing condition to produce the maximum biofuel using a 2k factorial level experimental design and to study the kinetics of the reaction. The experiment was performed in a laboratory scale 70-mL micro-reactor, and the obtained biofuel from the cracking process was analyzed by simulated distillation gas chromatography and gas chromatography-mass spectrometry. Furthermore, the fuel properties and elemental analysis of the biofuel were characterized. The effects of the temperature (420–460 °C), reaction time (45–75 min), catalyst loading (1–5% by weight; wt%) and an initial hydrogen (H2) pressure (100–500 kPa) on biofuel and gasoline yield were analyzed by analysis of variance. The main parameters were the reaction temperature and time. The optimum conditions, derived from using the design-expert software, was a reaction temperature and time of 444.4 °C and 45.50 min, respectively, with 1 wt% catalyst and an initial H2 pressure of 100 kPa to obtain a maximum yield of 76.2 wt% biofuel with 24.0 wt% gasoline. The acid value was decreased 3.9-fold to 13.5 mgKOH  g−1, whereas the heating value was increased 1.10-fold to 42.92 MJ kg−1, which is slightly lower than that for commercial diesel. The kinetics were determined based on experimental data for temperatures from 410 to 470 °C and best fitted to a second order rate with an apparent activation energy and pre-exponential factor of 86.0 kJ mol-1 and 181.3 s−1, respectively. The possible reaction pathway commenced from the hydrolysis of triglyceride to heavy oxygenated compounds followed by carboxylation, carbonylation and hydrogenation to become heavy linear hydrocarbons (HCs), then the heavy linear HC might be thermally and catalytically cracked into middle or small paraffins and olefins.