Dissertações em Química (Mestrado) - PPGQ/ICEN
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/16399
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Item Acesso aberto (Open Access) Obtenção de filmes finos de ligas de alta entropia à base de CoFeNi por eletrodeposição em meio aquoso(Universidade Federal do Pará, 2025-04-25) FREITAS, Gregório Felipe do Nascimento; NOCE, Rodrigo Della; http://lattes.cnpq.br/3734170057844016High-entropy alloys, also called multicomponent alloys, are alloys that have five or more elements whose composition is formed between 5% and 35% in terms of atomic composition of the elements. These alloys have gained prominence recently because they present very distinct and attractive properties in relation to conventional alloys composed of a single major element. In this context, the alloys have been produced by different physical and chemical methods. The present work addresses the subject of obtaining thin films of high-entropy alloys based on CoFeNi by the electrodeposition technique in aqueous medium, with additions of elements such as Mo, Mn, Sn and W. A simple and low-cost technique in relation to other methods proposed in the literature. By using the direct current (galvanostatic) method at room temperature and by varying the current density to obtain thin films in a range of 5 to 100 mA/cm2, the high entropy alloy CoFeNiMoW and the possibility of obtaining the CoFeNiMnSn alloy on a brass substrate (CuZn) are demonstrated. The electrodeposited films are characterized by Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Mossbauer Spectroscopy techniques. EDS analyses reveal that the composition of the alloys is strongly influenced by the applied current density. In the high entropy alloy with five elements CoFeNiMoW formed from applied current density of 50 mA cm-2, the atomic proportion obtained is Co 30%, Fe 21%, Ni 19%, Mo 25%, W 5%. For the CoFeNiMnSn alloy, its composition formed by means of a current density equal to 50 mA cm-2 is Co 26.2%, Fe 33.8%, Ni 5.5%, Mn 1.8%, Sn 32.6%, thus evidencing the formation of alloys with five elements by the proposed method.Item Acesso aberto (Open Access) Síntese de catalisador heterogêneo magnético básico aplicado no processo de produção de biodiesel(Universidade Federal do Pará, 2023-08-30) SANTOS, Hiarla Cristina Lima dos; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220This research focus on the development of a basic magnetic heterogeneous catalyst, using, for the first time, NaAlO2 as an active species supported in a magnetic material, CuFe2O4, being highly stable and effective to produce value-added products, such as biodiesel. With this purpose, a series of catalysts (x-NaAlO2/CuFe2O4) have been successfully synthesized by means of conventional and low-cost methods, such as coprecipitation and impregnation, each one being assessed in the soybean oil transesterification reaction. The features of the 25-NaAlO2/CuFe2O4 catalyst with the higher performance have been elucidated through techniques such as basicity by acid-base titration method, XRD, FTIR, SEM, EDS, TG/DTG and VSM. To optimize the biodiesel’s ester content, the face-centered central composite design (FCCD), integrated with the response surface methodology (RSM), was employed to assess the effect of the following aspects on the process: reaction temperature, MeOH:oil molar ratio, catalyst dosage and reaction time. The regression model presented R2 = 0.9394 and experimentally reached a maximum ester content of 95.9% (relative error < 5%) attributed to the biodiesel attained under the following optimal reaction conditions: temperature of 95 °C, MeOH:oil molar ratio of 13:1, catalyst dosage of 8% and time of 60 min. The NaAlO2/CuFe2O4 catalyst presented a stable catalytic performance during four transesterification cycles (>90.0%) and an efficient magnetic property for the catalyst separation and recovery process (Ms = 23.62 emu g-1). The results showed that the biodiesel’s physicochemical properties were in compliance with ASTM D6751 standard. Finally, this extensive study reveals the basic magnetic heterogeneous catalyst NaAlO2/CuFe2O4 as a practical and promising alternative to produce a sustainable biofuel.Item Acesso aberto (Open Access) Preparação e avaliação de catalisador heterogêneo ácido baseado em óxido de grafeno funcionalizado para síntese de biodiesel(Universidade Federal do Pará, 2021-09-24) SILVA, Paula Maria Melo da; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220The present study aims at the synthesis of a heterogeneous acid catalyst derived from graphene oxide, applied in the transesterification reaction of soybean oil to obtain biodiesel. The graphene oxide catalytic support was synthesized from graphite oxidation and the catalyst was functionalized by impregnation of molybdenum trioxide (MoO3) as the active phase. The synthesis of the support and the catalyst was confirmed through the characterization techniques of Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TG/DTG), Scanning Electron Microscopy (SEM), Energy Dispersion X-Ray Spectroscopy (EDS) and XRay Diffraction (DRX). The catalytic tests optimization of the transesterification reactions had as parameters evaluated the temperature in the range of 120–160 °C, the time between 1–5 h, the catalyst concentration comprised in 10% (m/m) and molar ratio oil/ alcohol in the range of 25:1–45:1. The reaction studies evidenced as an optimum point the temperature of 140 °C, time of 5 h, catalyst concentration 6% (m/m) and molar ratio of 35:1, leading to the obtainment of a biodiesel with an ester content above 90%. The catalyst also maintained its catalytic activity even in the seventh reaction cycle. Therefore, the results obtained demonstrate that the graphene oxide catalyst supported by MoO3 is a new and promising heterogeneous acid catalyst with high catalytic efficiency in the transesterification reaction for the biodiesel synthesis.Item Acesso aberto (Open Access) Estudo químico e atividades biológicas dos extratos do fungo actinomucor elegans accc18.1a endofítico de rhizophora mangle l. (rhizophoraceae)(Universidade Federal do Pará, 2024-02-26) PADILLA, Kathia Raquel Murillo; MARINHO, Patrícia Santana Barbosa; http://lattes.cnpq.br/4826647905254039; HTTPS://ORCID.ORG/0000-0002-9368-8574; MARINHO, Andrey Moacir do Rosário; http://lattes.cnpq.br/2511998363000599; https://orcid.org/0000-0002-8981-0995The study of underexplored natural sources, especially in the Amazon region, has gained significance in recent years. Considering the Amazon as the largest forest in the world, it is notable that many species still remain undiscovered. In this context, research on secondary metabolites of endophytic fungi has sparked growing interest in the scientific community, driven by the potential these microorganisms hold in the field of health. Microorganisms have been a rich source of bioactive metabolites with various applications such as agrochemicals, antibiotics, immunosuppressants, antiparasitic, and anticancer agents. The aim of this study was to contribute to the investigation of endophytic fungi in mangrove plants of the Brazilian Amazon through the isolation and identification of compounds with antimicrobial, allelopathic, and anticancer activities from the fungus Actinomucor elegans AcCC181A, which was isolated as an endophyte from the plant Rhizophora mangle L. (Rhizophoraceae). Using chromatography techniques, the phenolic compounds tyrosol (S-1), 4-hydroxyphenylacetic acid (S-2), 4-formylphenyl 2-phenylacetate (S-3), and phenylacetic acid (S-4) were isolated. From tyrosol, the substances 4-(2-acetoxyethyl)-phenylacetate (S-5), 4-(2-(butyryloxy)ethyl)- phenylbutyrate (S-6), and 4-(2-(benzoyloxy)ethyl)phenylbenzoate (S-7) were obtained through structural derivatization. The structures of the substances were elucidated using Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) techniques. The substances and crude extract were tested against the bacteria E. coli, Bacillus subtilis, S. typhimurium, S. aureus, and Xanthomonas axonopodis pv. passiflorae, showing antimicrobial activity results. Cytotoxicity and cell viability assays of the isolated substances S-1, S-2, and S-3 were also performed. All tested substances demonstrated potential cytotoxic activity on gastric cancer cell lines. Additionally, the allelopathic potential of the crude extract was evaluated, showing activity with lettuce seeds. It is important to note that compounds S-6, S-3, and S-7 are being tested for the first time in antimicrobial assays. Furthermore, it is relevant to emphasize that this study represents the first report of antimicrobial assays conducted with the substances isolated in this work against the bacteria Xanthomonas axonopodis pv. passiflorae.Item Acesso aberto (Open Access) Síntese de biodiesel utilizando catalisador bifuncional baseado em ferrita com óxido metálico suportado(Universidade Federal do Pará, 2021-07-23) GONÇALVES, Matheus Arrais; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220In this study, a solid magnetic acid catalyst MoO3/SrFe2O4, composed of molybdenum oxide (MoO3) supported on strontium ferrite (SrFe2O4), was synthesized and applied in the transesterification of waste cooking oil (WCO). The catalyst was characterized by acid-base titration method in order to determine Surface acidity, Thermogravimetric analysis (TG/DTG), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersion X-ray spectroscopy (EDS) and Vibrating sample magnetometry (VSM) techniques. A central composite design of centered face 24 (FCCD) and a mathematical model was developed in order to describe the behavior of the ester content as a function of the independent variables temperature, alcohol:oil molar ratio, catalyst dosage and time reaction. The mathematical model (R2=0.9900) was validated and showed a relative error below 5% between the experimental and predicted values. Using linear regression methods and response surface methodology (RSM) the conditions of biodiesel synthesis reaction were optimized and 95.4% conversion into esters was obtained from the use of the reaction temperature of 164 °C, alcohol:oil molar ratio of 40:1, catalyst dosage of 10% and reaction time of 4 h . The catalyst showed high reusability, since it was possible to use it in 8 reaction cycles which it is an indication of its good prospectus for development and application as bifunctional catalyst.Item Acesso aberto (Open Access) Influência do ph do banho e da densidade de corrente no comportamento capacitivo de eletrodos de mno2 obtidos por eletrodeposição anódica(Universidade Federal do Pará, 2025-01-30) RENTE, Arthur de Farias Silva; NOCE, Rodrigo Della; http://lattes.cnpq.br/3734170057844016MnO₂ electrodes are obtained by anodic electrodeposition on stainless steel substrate at room temperature from a 0.1 M manganese sulfate bath, under different current densities, ranging from 200 µA·cm⁻² to 5 mA·cm⁻² (galvanostatic mode), and pH values from 2 to 6. The material morphology is analyzed by scanning electron microscopy, revealing compact, homogeneous, and two-dimensional film deposition, with the presence of microcracks that provide active sites for the incorporation of sodium sulfate (Na₂SO₄) electrolyte ions, enhancing the material's specific capacitance. At low current densities, such as 200 and 500 µA·cm⁻², the formed film is homogeneous, while increasing the current density to 2 mA·cm⁻² results in cracks on the material's surface. Morphological changes are also identified as a function of pH: near neutrality (pH 6), cracks become evident, whereas in more acidic pH levels, such as 2 and 3, the structure remains uniform. At pH 4, an irregular structure is observed. The structure of the formed films, analyzed by by X-ray diffraction, reveals the presence of the alpha (α) phase under all studied conditions, regardless of the applied current density and bath pH. Electrochemical characterization of the films, carried out using cyclic voltammetry and charge-discharge curves (chronopotentiometry), indicates a working potential window of 1.1 V and specific capacitance values ranging from 13 to 371.8 F·g⁻¹, depending on the applied current density and bath pH. The highest specific capacitance value is obtained at a current density of 2 mA·cm⁻² and pH 4.Item Acesso aberto (Open Access) Atividade e estabilidade de catalisador à base de carbono sulfonado na reação de esterificação: influência da temperatura de pirólise no processo de funcionalização(Universidade Federal do Pará, 2021-08-25) CORRÊA, Ana Paula da Luz; CONCEIÇÃO, Leyvison Rafael Vieira da; http://lattes.cnpq.br/7467898936995220In the present study, the pyrolysis temperature on the activity and catalytic stability of sulfonated biochars, from the agroindustrial waste of murumuru kernel shell, was evaluated in the esterification reaction of oleic acid with methanol. In view of the investigation of factors related to catalytic functionalization and its impact on reuse processes, carbonaceous materials were synthesized by direct pyrolysis under different carbonization temperatures, at 450, 600 and 750 °C. The process of biochars functionalization was carried out by sulfonation with concentrated sulfuric acid at 200 °C and 4 h. The materials were characterized in terms of determining the density of sulfonic groups, Scanning Electron Microscopy (SEM), Energy Dispersion X-Ray Spectroscopy (EDS), Elemental Analysis (CNHS), Fourier Transform Infrared Spectroscopy (FT- IR), Raman Spectroscopy, Thermogravimetric Analysis (TG) and X-Ray Excited Photoelectron Spectroscopy (XPS). The influence of the variables temperature and reaction time on the catalytic performance and reuse capacity of the catalysts was also evaluated. The data obtained showed that the functionalization with sulfonic groups occurred directly in the carbon chain of the biochars, higher temperatures carbonization resulted in more stable polycondensed carbonaceous catalysts and a higher degree of structural order. The carbonized catalyst at 750 °C achieved the conversion of oleic acid in the esterification reactions of 98.37% and maintained in the third reaction cycle conversion of 89.30%. Such a catalyst also has the highest content of sulfur groups, even after reuse processes. The increase in temperature and time in the reaction medium was able to improve the reuse capacity of relatively low stability catalysts. Thus, these results show the impact of the pyrolysis temperature in obtaining catalysts with greater activity and catalytic stability in the esterification reactions, and in this way provide great support for the development of new heterogeneous sulfonated carbon-based catalysts, applied in the biodiesel production process. Furthermore, they corroborate the high potential for using the residual biomass of murumuru kernel shell in the development of a new material.Item Acesso aberto (Open Access) Estudo fitoquímico e avaliação do potencial antimicrobiano e antioxidadnte das folhas de metrodorea flavida k. krause(Universidade Federal do Pará, 2023-09-29) CONCEIÇÃO, Carlos Maurício Nunes de Souza da; PINHEIRO, Wandson Braamcamp de Souza; http://lattes.cnpq.br/8867866033296703; SANTOS, Lourivaldo da Silva; http://lattes.cnpq.br/3232898465948962; SILVA, Milton Nascimento da; http://lattes.cnpq.br/6742390457977989; https://orcid.org/0000-0001-9755-4058The species Metrodorea flavida K. Krause, popularly known as three leaves, belongs to the Rutaceae family, and is an endemic species of the Amazon biome. Despite belonging to a taxon of economic and medicinal relevance, in addition to being located in one of the regions of the planet with the greatest biotechnological relevance, there is still a scarcity of studies focused on the phytochemistry of M. flavida for this species. Therefore, this work sought to contribute to the phytochemical study of this species, through the determination of the chemical, chromatographic and spectroscopic profiles of M. flavida extracts, the isolation and structural elucidation of the major compounds, as well as the evaluation of antioxidant potentials. and antimicrobial from M. flavida leaf extracts. Firstly, microextractions were carried out from the plant leaves with the solvents ethyl acetate, 96% ethanol and 70% ethanol. After analyzing the profiles obtained by High Efficiency Thin Layer Chromatography, High Efficiency Liquid Chromatography (HPLC), by Nuclear Magnetic Resonance and antioxidant and antimicrobial tests with the extracts, an extraction was carried out by maceration using 70% ethanol, of this extract. fractionation occurred with Solid Phase Extraction, resulting in 23 fractions, of which the constituents of fraction 60%V1 were purified by high-performance liquid chromatography, as well as the isolated substances were elucidated by 1D Nuclear Magnetic Resonance (NMR) spectroscopy and 2D. The chemical profiles of the M. flavida extracts indicated the presence of substances from the classes of terpenes, flavonoids and coumarins, the antioxidant tests of the extracts demonstrated that the microextract obtained with 70% ethanol presented greater efficiency in scavenging DPPH• radicals, in addition, for antimicrobial tests, the microextract obtained with ethyl acetate showed the best results for strains of Staphylococcus aureus, Bacillus subtilis and Escherichia coli. The 70% ethanol macerated extract was also tested for the same strains mentioned above and showed bactericidal action for S. aureus, B. subtilis and E. coli, in addition to bacteriostatic action for Salmonella typhimurium. From the 60%V1 fraction, five substances were isolated (S1, S2, S3, S4 and S5), which after analysis by NMR and thorough research on the Scinfinder and PubChem platforms, it was found that substances S2 and S4 are treated of two new dihydrochalcones, isolated for the first time from plants. In this way, the data obtained represent a contribution to the study of phytochemistry and the biological properties of the species M. flavida, as well as to the natural product chemistry, since two new natural compounds were discovered.Item Acesso aberto (Open Access) Materiais de interações biocarvões/latossolo: caracterização química e físico-química(Universidade Federal do Pará, 2019-04-17) MACHADO, Marcelly Christian Galvão Rodrigues; MORAES, Milena Carvalho de; http://lattes.cnpq.br/9699850614353792; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008The present study aims to obtain materials from thermochemical interactions biochars-latosoil and to evaluation its chemical and physicochemical properties inrelation to those indicated in high fertility soils. The key importance of this study involves: characteristics indicative of soil with high organic matter stability, as to those indicated for archeological black earth (ABE), due to the structural properties from crystalline and amorphous materials, associated to the organic aggregates, considered natural adsorbent in soils. The sources of biochar were leaves of cinnamon, cacau, cashew and ipê trees and to those for soil was latosoilsample fromthe Caxiuanã region/ Brazil-Pará. The characterization of the materials was performed based on analysis by spectral analytical methods [XRD, FTIR, EDS and MIRO-RAMAN].The results from XRD indicatedspecially characteristics of organic compounds, represented by hexagonal and rhombohedral graphites, turbostratic graphite and graphite oxide. Based elementaryanalysis were obtained atomic ratio O/C corresponding to carbonaceous materials with high aromaticity. Micro-Raman spectra shown bands D e G corresponding to HPA´s pyrene and naphthalene. The following conclusions were obtained: the materials from thermochemical interactions biochars-soil presents chemical and physicochemical properties corresponding to the organic aggregates common in soil with high stability; the presence of HPAs into materials shoud be considered negativefor to use biochars into soils, due to the possibility of contamination of the soil and groundwater.