Avaliação voltamétrica da conversão do óleo de babaçu (orbignya phalerata) em biodiesel

Abstract

The present work proposes the evaluation of electrochemical procedures for the monitoring of the conversion of babassu oil to biodiesel through glycerol analysis. Firstly, a study was carried out to evaluate the best biodiesel / water ratio for the extraction of glycerol in order to verify if the variation in biodiesel and water ratios directly influence the voltammetric response of glycerol. Subsequently, a study on the oxidation of glycerol was carried out. The electrochemical measurements were performed in a potentiostat/Autolab PGSTAT12 galvanostat coupled to a three electrode electrochemical cell: platinum disk (working electrode), a platinum wire (auxiliary electrode) and Ag/AgClSat (reference electrode). The electrochemical behavior of the glycerol oxidation was evaluated in different electrolytes by means of cyclic voltammetry, with the best conditions being established for analysis in 0.1 mol L-1 BR buffer medium (pH 12). In this medium, the glycerol had an oxidation peak around -200 mV. The analytical feasibility of the determination of glycerol in biodiesel samples was studied by means of differential pulse voltammetry and in this technique some operational parameters were optimized: deposition time (30s), deposition potential (-500 mV) and pulse amplitude (150 mV), whose values provided good electroanalytical results. After 20 minutes of reaction (time chosen as sufficient for the formation of glycerol), the analyte was extracted into the aqueous phase, as determined by the optimized voltammetric procedure. An analytical and statistical evaluation showed good linearity (r = 0.996), sensitivity (3.03 μA/mol L-1), precision (1.02% to 3.16%), detection limit (0.01 mmol L-1) and quantification limit (0.04 mmol L-1). The accuracy of the procedure was evaluated by the percentage recovery of glycerol, whose recovery values varied between 99 and 113% and indicate that the proposed method is accurate and suitable for glycerol analysis during the transesterification process.