http://hdl.handle.net/11422/59 Mon, 13 Apr 2026 11:37:04 GMT 2026-04-13T11:37:04Z http://hdl.handle.net/11422/28990 Title: Estudo de extratos de Armoracia rusticana e wasabi comercial como inibidores de corrosão do aço em meio HCl 1M usando MALDI-TOF Author(s)/Inventor(s): Nascimento, Iendel Rubio do Advisor: D’Elia, Eliane Abstract: Corrosion studies were performed using extracts of A. rusticana, commercial wasabi and their fractions through mass loss measurements, electrochemical impedance, and potentiodynamic polarization at concentrations of 100, 200, 400, 800, 1600, and 3200 mg L−1 in 1 mol L−1 HCl. The FT-IR, ESI-MS(±), MALDI-FT-ICR(±), and MALDI-TOF(±) techniques were used for the chemical characterization of the extracts and their fractions. The ethyl acetate fraction of crude ethanolic extract (WEP-EtOAc) showed the highest inhibition efficiency, above 96%, verified by mass loss measurement with and without temperature variation and electrochemical tests. SEM and XPS analyses were performed for surface analysis. MALDI-TOF was also used for the ethyl acetate fraction of WEP, where the laser was applied directly to the metal plate under study. Even after washing, the glucosinolate chemical group was identified as the major component on the metal surface. This study suggests that glucosinolates are the possible main corrosion-inhibiting phytochemicals in the extract. Publisher: Universidade Federal do Rio de Janeiro Type: Tese Wed, 01 Jan 2025 00:00:00 GMT http://hdl.handle.net/11422/28990 2025-01-01T00:00:00Z http://hdl.handle.net/11422/28984 Title: Estudo de novos inibidores de corrosão com base em pontos quânticos de carbono co-dopados com N e Nb Author(s)/Inventor(s): Vita, Filipe dos Santos Advisor: D’Elia, Eliane Abstract: Corrosion is a recurring problem in metallic materials in various sectors of a country, such as industry, construction, health, transportation, and the like, generating annual costs that can reach 1 to 5% of GDP. In addition, this process tends to become even more aggressive with acidity and increased temperature of the environment where the material is inserted. In this context, the industry has been seeking alternatives to avoid the degradation and uselessness of carbon steel, an affordable, versatile alloy with excellent properties, which makes it the main alternative in the industrial sector. Therefore, this work aimed to synthesize and develop carbon quantum dots co-doped with nitrogen (N) and niobium (Nb) as new corrosion inhibitors for carbon steel parts in an acidic environment. The doped carbon quantum dots were obtained by the bottom- up route via thermal decomposition at 200 C, varying the amounts of the precursors citric acid, urea, and niobium ammonium oxalate. The inhibitory effect on the corrosion of carbon steel in a solution containing HCl 1 mol L -1 was compared. The gravimetric tests revealed that the inhibition efficiency of 100 mg L -1 of N-CD obtained with 1 g of urea and 5 g of citric acid and 100 mg L-1 Nb,N-CD obtained with the same citric acid and urea proportion with the addition of 2 g of niobium ammoniacal oxalate, for 6 hours of immersion at 25 oC, reached more than 80% with Nb,N-CD maintaining approximately this value at higher temperatures, while the N-CD had the inhibition efficiency decreased abruptly with temperature. TGA (Thermogravimetric Analysis) and DTA (Differential Thermal Analysis) were used to describe the thermal stability of the CDs and showed that the Nb addition to CDs improves their termal stability. The functional groups and suggested composition were verified using FTIR (Fourier Transform Infrared Spectroscopy), XPS (X-ray photoelectron spectroscopy), and XRF (X-ray Fluorescence) proving the presence of N and Nb in the CDs. Isotherm studies demonstrated that N-CD and Nb,N-CD obeyed the Langmuir adsorption isotherm and the eletrochemical measurements of impedance and potentiodynamic polarization showed that the CDs inbihited both anodic and cathodic reactions with IE of 84-85% for 200 ppm inhibitor. A series of experimental results demonstrated that niobium doping influenced the particle size, termal stability, and fluorescence, among other properties of the synthesized quantum dots, maintaining a high inhibition efficiency at high temperatures. These results reveal that using nitrogen and niobium doped CDs is a new and effective alternative to mitigate corrosion in carbon steel exposed to 1 mol L-1 HCl, especially at temperatures above room temperature. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação Wed, 02 Apr 2025 00:00:00 GMT http://hdl.handle.net/11422/28984 2025-04-02T00:00:00Z http://hdl.handle.net/11422/28941 Title: Maturação artificial: hidropirólise em menor escala Author(s)/Inventor(s): Silva, Lucas de Souza Advisor: Gonçalves, Vinicius Ottonio Oliveira Abstract: Hydrous pyrolysis is a type of experiment that involves the heating of samples in a closed reactor system with the addition of liquid water. In it, certain amounts of gravel-sized source rocks are added to the system along with an appropriate amount of liquid water to ensure that these rocks are completely submerged before, during, and after the experiment, because contact with water is required for oil to form from thermal cracking reactions of kerogen and bitumen, by providing hydrogen atoms that are necessary for these reactions to occur. This oil accumulates on the water surface of the system after the experiment and is chemically similar to oils obtained from natural sources, allowing the use of hydrous pyrolysis to correctly simulate and understand the process of oil generation, expulsion, and migration. Since there are four stages of petroleum formation (pre-oil, incipient-oil, primary-oil, and post-oil generation), different experimental conditions are used to ensure that all stages are covered to correctly simulate oil and gas formation from a particular source rock. These conditions involve high temperatures (280-365°C) and pressures (due to the water at high temperatures in the system), along with an experiment duration of 72 hours. Typically, 1-liter reactors are used in hydrous pyrolysis experiments; however, in this work, a 250-milliliter reactor was also used to compare the amount of products generated and to verify if it is possible to adapt normal hydrous pyrolysis experiments into this smaller reactor, since an amount four times smaller of rocks and water (or a 5% wt. NaCl solution) are used, allowing more experiments to be conducted, especially in cases where the amount of rocks available is very low. After comparing product (oil and gas) yields, bitumen extracted from recovered rocks and mineral characteristics from rocks used in both reactors and with results reported by Spigolon et al. (2015), there were no significant differences with the use of a smaller reactor, indicating that using a lower-capacity reactor does not interfere with the ability of hydrous pyrolysis to simulate petroleum formation and expulsion. Since using a 250-milliliter reactor results in almost the same amount of products, it is an improvement, especially because it reduces the amount of sample required to conduct all the necessary experiments, it is easier to handle and requires less labor due to its lower total weight. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação Wed, 26 Feb 2025 00:00:00 GMT http://hdl.handle.net/11422/28941 2025-02-26T00:00:00Z http://hdl.handle.net/11422/28934 Title: Mecanismos da oxidação de álcoois por N-haloreagentes e metodologia de ciclização oxidativa de dióis à lactonas por ácido tricloroisocianúrico Author(s)/Inventor(s): Santos, Carlos Vinícius Pinto dos Advisor: Mattos, Marcio Contrucci Saraiva de Abstract: The DFT investigation of alcohol oxidation by NBS in aqueous acetic acid (30-70%) found mechanisms that differed only in the amount of explicit solvent. The alcohol was oxidized via hydride abstraction by NBS with basic acetate catalysis; acid catalysis was shown to be possible but was outside the reaction scope. The kcalc and ΔG≠ calc values in the 20 cases studied agreed fully with available kinetic data. The theoretical study of the mechanism of oxidation of alcohols by TCCA (based on a previous kinetic study) found a mechanism in which autocatalytic Cl2 abstracted hydride in an acyclic transition state in the induction zone. Alcohols with strongly electron-withdring groups, which were outside the linear free energy relationship, underwent oxidation through hydrogen abstraction by chloride from the respective benzyl hypochlorite. Furthermore, it was possible to suggest the continuity of the mechanism between aromatic and secondary alcohols at the M06-2x/6-311G(d,p) level. The ipso substitution study in the reaction with TCCA (11 cases) identified the position and leaving group as reaction limiters. The DFT study demonstrated that the higher incidence of ipso substitution in 4- methoxybenzyl alcohol at 0 °C as opposed to 25 °C occurred due to the decrease in ΔG≠ calc for ipso substitution and the increase in ΔG≠ calc for concurrent reactions. A cost-effective, safe, and convenient methodology for oxidative cyclization of diols to lactones using TCCA, H2O/Py in a 30% MeCN/CH2Cl2 solution at room temperature was proposed. Yields of 50-98% were obtained for six examples of small ring lactones and one example of a medium-sized ring lactone (decanolactone). The oxidation of 1,4-pentanediol by TCCA led to the ketone, while oxidation by TBCA/Py in acetonitrile led to γ-butyrolactone without the formation of a ketone. The mechanism study by DFT identified two concomitant mechanisms through the cyclization of acyl chloride or the oxidation of lactol with acidic medium. Publisher: Universidade Federal do Rio de Janeiro Type: Tese Thu, 06 Feb 2025 00:00:00 GMT http://hdl.handle.net/11422/28934 2025-02-06T00:00:00Z