Optimization of heterogeneous bio-based catalysts and synthesis of inorganic equivalent for large-scale biodiesel production

Abstract

This research focuses on optimizing the production of biodiesel to reduce overdependence on fossil fuels by utilizing waste resources. In recent years there have been concerns on the use of fossil fuels in the increasing demand of energy and its drawbacks. Fossil fuels, unlike biodiesel, are carbon rich and hence on combustion, releases excessive amounts of CO2, NOX and SOX leading to global warming. In this research, waste cooking oil (WCO) and ethanol were used as the main raw materials to produce biodiesel known to have net zero carbon emission potential to meet Canada’s commitment to attain net zero carbon emissions by 2050. In providing alternative use for waste resources, waste eggshells, cow bones, fish scales and banana peels were investigated, characterized and optimized to manufacture high performing Lewis base catalysts to obtain high biodiesel yield in a transesterification reaction. Initially eggshell, fish scale and cow bone catalysts all of which are primarily calcium based were studied and optimized by varying mix procedure, mix ratio as well as impregnating 1%, 5% and 10% by weight of potassium promoters. Physical mixing, 1:6:3 (ES: FS:CB) mix ratio, 10% potassium impregnation were the obtained optimum and a 75% biodiesel yield was obtained when 1:6:3 + 10% K catalyst was used. Due to the low biodiesel yields obtained there was a need to investigate other biobased materials with Lewis base potential. This led to the shift to potassium based biobased material, banana peels for optimization and use as transesterification catalyst. The banana peels were calcined at 600℃ (BP600), 800℃ (BP800), 900℃ (BP900) and 1000℃ for optimization. The yield on calcining at 1000℃ was not enough to carry out a reaction. BP900 had the best performance yielding up to 96.16% biodiesel. An inorganic replica of the optimum biobased catalyst BP900 was prepared using inorganic precursors due to the drawbacks of the biobased catalyst (low calcination yield of 10%, not available in large commercial quantities) via co-impregnation (BPIn1) and coprecipitation methods (BPIn2). BPIn 2 had a biodiesel yield of 84.58% and was used for further studies. The effect of reaction time, temperature, catalyst amount and ethanol to oil ratio (E:O) on the biodiesel yield were checked and the optimum conditions were 6 hours, 70℃, 2wt%, 21:1 respectively. The viscosity, acid value and density were determined according to ASTMD, and results were within acceptable standards. TGA, XRD, SEM/EDS, N2 Physisorption and CO2 TPD analysis were performed on catalysts to determine their characteristics. Kinetic data was obtained for BPIn2 catalyst by varying the E:O, reaction time and reaction temperature for 2wt% catalyst dose runs to obtain various biodiesel yields. NLReg software was used to regress the data to obtain an activation energy (Ea) of 39.07kJ/mol, collision factor (k0) of 1.5*106 /gcat.h. mol5.6, an order with respect to ethanol (e) of 3, and an order of reaction with respect to oil (o) of 2.