Produção de biodiesel a partir de óleo residual de fritura e sua valorização química: transesterificação, epoxidação e análise experimental

Abstract

Waste cooking oil is a low-cost and widely available lipid feedstock whose valorization contributes to mitigating environmental impacts associated with improper disposal. In this context, this thesis aimed to investigate the Production of biodiesel from waste cooking oil and its subsequent chemical upgrading through the epoxidation of fatty acid esters, adopting an integrated approach aligned with circular economy and biorefinery principles. Initially, alkaline transesterification of waste cooking oil was evaluated using both methyl and ethyl routes, employing a central composite rotational design (CCRD 2³) combined with statistical modeling to assess the influence of operational variables on total ester content. The results demonstrated high conversion efficiency for both routes, with maximum ester contents of approximately 97.5% (methyl route) and 99.3% (ethyl route), meeting current regulatory specifications. Statistical analysis indicated that catalyst Concentration was the most significant variable, with a predominant quadratic effect. The methyl route exhibited better model fitting (higher R² and no significant lack of fit), indicating greater robustness and operational predictability, whereas the ethyl route showed higher data dispersion and viii sensitivity to process conditions, associated with phase behavior and emulsion formation. The developed models enabled the identification of optimal operating regions and provided insights into process limitations. In the subsequent stage, the produced biodiesels were subjected to epoxidation using in situ generated peracetic acid. The conversion of double bonds was monitored by quantitative proton nuclear magnetic resonance (¹H NMR), revealing a non-linear behavior as a function of oxidant concentration. Maximum conversions of approximately 74.3% for methyl esters and 80.6% for ethyl esters were obtained under intermediate peracetic acid Concentrations. At higher concentrations, a decrease in Conversion was Observed, attributed to secondary reactions involving oxirane ring opening. Comparative analysis indicated that the differences between methyl and ethyl systems are not directly related to the intrinsic reactivity of double bonds, but rather to physicochemical factors of the reaction medium, such as polarity, solubility, and phase behavior. Overall, the results demonstrate the feasibility of using waste cooking oil as a feedstock for the production of high-quality biodiesel and its subsequent conversion into higher value added epoxidized derivatives, highlighting the potential of this route for applications in Biolubricants and other renewable-based products.