Biodiesel Production from Waste Cooking Oil Using Two-Dimensional Photocatalysts: Optimization of Process, Mechanism and Kinetics Study

Diesel fuel can be substituted with biodiesel fuel. Burning biodiesel results in less pollution because its source is vegetable or animal fat. Waste cooking oil (WCO) was utilized in this study as a raw source to produce biodiesel. In the WCO under study, the percentage of free fatty acids (FFAs) was 4.09%. The process of turning used cooking oil waste into biodiesel involved two steps. The initial phase was studying the photocatalytic esterification of methanol with FFAs in WCO under visible irradiation using Cr (x%)-TiO2. Triglycerides and methanol were transesterified in the second stage, which was catalyzed by NaOH. When TiO2 was present, efficiency was shown to increase by 10% when compared to the absence of a photocatalyst. Cr-TiO2 photo-esterification reaction has an equivalent order of one. The realisation of the reaction under mild conditions was confirmed by the activation energy of 31.36 kJ/mol needed for the Cr-TiO2 photocatalyst to photo-esterify WCO. Our hypothesis for the esterification process took into account the formation of H+, CH3OO·, and R-COOH on the photocatalyst surface. OH- was thought to be the active species in the transesterification reaction process. The density of the produced biodiesel was 0.89 g.cm-3, per the data that were obtained. For biodiesel, the results yield a falling point of -5 and a cloud point of 0, respectively. The biodiesel made from waste oil had a viscosity of 4.1 mm2.s−1, which was within the standard range. The biodiesel sample made from waste oil has an acid value of 0.38 mg KOH