Navegando por Autor "Silva, Leticia Milena Gomes da"
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Dissertação Electroconversion of waste from the biofuel industry into value-added products by electrochemical oxidation and hydrogen cogeneration(Universidade Federal do Rio Grande do Norte, 2024-10-11) Silva, Leticia Milena Gomes da; Huitle, Carlos Alberto Martinez; Gondim, Amanda Duarte; http://lattes.cnpq.br/2485073932883264; http://lattes.cnpq.br/7352781150499720; Araujo, Danyelle Medeiros de; Santos, Elisama Vieira dos; Menezes, Fabricio GavaThe environmental impacts generated by the use of fossil fuels and the energy insecurity associated with this have led to an increase in the production of biofuels. Consequently, an increase in the amount of glycerol generated as a by-product of transesterification reactions is also expected, which could result in an accumulation of residues containing this polyalcohol. Several techniques have been used to convert glycerol into products with high added value, including electrochemical oxidation, which stands out for the diversity of products that can be formed. Therefore, this work proposes to investigate the application of electrochemical oxidation for the conversion of glycerol, thus obtaining products with greater added value, such as carboxylic acids and green hydrogen. To this end, oxidation was studied under different conditions, seeking greater production of these products. The conversion of glycerol was monitored by ionic chromatography and chemical oxygen demand. The results obtained are divided into two chapters. Initially, in the second chapter, the optimization process to obtain the most favorable condition for glycerol oxidation is presented. In this study, the effects of current density, electrolyte concentration and oxidation time were evaluated, using DSA (Dimensionally Stable Anodes) as the anode for the oxidation of 0.1 mol L⁻¹ of glycerol. Note that the current density of 90 mA cm⁻², with a supporting electrolyte concentration of 0.1 mol L⁻¹ and oxidation time of 480 minutes, was the best condition for the conversion of glycerol, generating 256.21 and 211.17 mg L⁻¹ of formic acid using, respectively, undivided and divided cells. 6.77 L of dry hydrogen were also produced in the split cell. In this work, the oxidation of a real sample was also evaluated, obtained from the biofuel washing process, which, in the best condition, produced 490.69 mg L⁻¹ of formic acid and 47.51 mg L⁻¹ of acid acetic acid using undivided cells, and 567.39 and 384.02 mg L⁻¹ of formic acid and acetic acid, respectively, when using divided cells. Then, in the third chapter, the oxidative process was evaluated using different anode materials, DSA and BDD (Boron Doped Diamond), and the influence of different electrolytes. In this study, the production of carboxylic acids and green hydrogen were evaluated using split and non-split electrochemical cell configurations, with a current density of 90 mA cm⁻² and 0.1 mol L⁻¹ of supporting electrolyte for 360 minutes. The production of carboxylic acids was more efficient using NaOH as supporting electrolyte for both electrodes, generating 958.62 and 928.37 mg L⁻¹ of formic acid and 1358.75 and 1096.91 mg L⁻¹ of oxalic acid for cells unsplit and split, respectively, when BDD was used as the anode. The condition that presented the highest amount of formic acid was used for the oxidation of two real samples from the disposal of biodiesel production, with residual glycerol, the production of formic acid was 117.41 and 318.21 mg L-1 using undivided cells and respectively, the second real sample comes from biodiesel washing water and this same condition studied in a production of 1618.05 mg L⁻¹ of formic acid using undivided cells and 1462.55 mg L⁻¹ using divided cells. Hydrogen production was independent of the anode material and the type of electrolyte used. Finally, it is concluded that the electrochemical oxidation process is an effective and viable alternative for the production of carboxylic acids, which are products of economic interest for the chemical and pharmaceutical industries.