http://repositorio.ufc.br/handle/riufc/461 2026-04-10T14:58:48Z http://repositorio.ufc.br/handle/riufc/85728 Título: Estudo integrado da macaúba (Acrocomia aculeata): caracterização físico-química, pirólise termogravimétrica lenta e de determinação da energia de ativação por métodos isoconversionais Autor(es): Coimbra, Kennedy Romualdo Guedes Abstract: The continuous use of fossil fuels, the growing concern with global warming, and environmental pollution have driven the search for renewable energy sources and alternative technologies. In this context, the use of lignocellulosic biomass, such as macaúba (Acrocomia aculeata), has stood out as a promising renewable raw material to produce bioenergy and biofuels through thermochemical conversion. This study investigated the fractions of macaúba (epicarp, mesocarp, endocarp, and almond cake) through physicochemical analyses and, by means of thermogravimetric pyrolysis, the reaction kinetics. Proximate and ultimate analyses indicated that the mesocarp has the highest volatile content (87%) and a higher heating value (HHV) of 22 MJ/kg, being the most promising fraction for slow pyrolysis. FTIR analyses confirmed the predominant presence of cellulose, hemicellulose, and lignin. Thermogravimetric analyses were carried out in an inert atmosphere with heating rates of 5, 10, 15, and 20 °C/min, showing that mesocarp and epicarp decompose rapidly between 250 and 400 °C, while endocarp and almond press cake present slower degradation, up to 600 °C. With the pyrolysis kinetics, the activation energy (Ea) was calculated using the isoconversional methods of Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO), presenting average values of 186 to 202 kJ/mol for the mesocarp and 232 to 235 kJ/mol for the endocarp. Under oxidative atmosphere, the almond press cake reached Ea values up to 342 kJ/mol. The results validated the potential of macaúba for energy applications with integrated residue utilization, with epicarp and mesocarp indicated to produce bio-oil and endocarp and almond press cake to produce biochar. Tipo: Dissertação 2025-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/84215 Título: Análise de desempenho e emissões de simulações de caminhões híbridos elétricos com autonomia extendida (REEV) Autor(es): Uchoa Filho, Francisco Elmo Lima Abstract: The worsening global climate crisis demands urgent strategies to mitigate environmental impacts in a wide range of human activities. The transport sector is responsible for around 23% of all global CO 2 emissions, and of this total, 29.4% comes from trucks. On the other hand, little research has been conducted on this transport mode. Given the global trend toward the adoption of electric trucks, the strategies adopted in many countries are evaluated. Brazil’s history with biofuels, especially ethanol, indicates that range extended electric vehicles (REEV) are the ideal solution for the country. This work proposes a study of the performance of different truck configurations with power trains (the set of components responsible for propelling the vehicle) in the REEV configuration. Four truck models are proposed, two with a maximum load of 23t and two with 57t, three power levels for the ethanol-powered combustion engine, combined with up to 17 different groups of battery banks in parallel. Thus, one-dimensional powertrain models are developed on the Realis Ignite platform based on commercial components and vehicles. Aided by routines developed in Python, the various powertrain configurations are simulated in successive standardized driving cycles. The combinations with the lowest specific energy consumption are selected, being the minimum 0.633MJ/t.km. The emissions of CO 2 , NO x , CO, and HC were evaluated according to national standards, equivalent to Euro VI, with all simulations being in compliance. Tipo: Dissertação 2025-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/83444 Título: Síntese e caracterização de óxido de grafeno reduzido preparado a partir de grafite natural via método hummers modificado Autor(es): Freitas, Nichollas Rodrigues Bezerra Tipo: Dissertação 2024-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/82707 Título: Análise da resistência e do desempenho de membranas de troca protônica (PEM) à base de quitosana sob variação de temperatura Autor(es): Braga, Marcelo Rocha Abstract: This work investigates the fabrication and performance of chitosan-based membranes for hydrogen PEM fuel cells. The search for renewable energy sources has been increasing steadily in recent times, with a growing interest in hydrogen-based energy generation mechanisms, among which the so-called PEM (Polymer Electrolyte Membrane) fuel cells stand out. These cells, through a polymeric membrane, allow the migration of hydrogen protons from the anode to the cathode, where they combine with oxygen, generating energy and water as products. Various materials can be used for the fabrication of this membrane; in this study, the focus was placed on developing an organic membrane based on chitosan, doped with different reagents. Performance and resistance tests were conducted under increasing temperatures to evaluate the viability of this low-cost organic compound for the market. The methodology involved dissolving chitosan and polyvinyl alcohol (PVA) mixtures in a solution of sulfosuccinic acid (SSA) and hydrochloric acid, followed by drying and treatment with sulfuric acid. The resulting membranes were then used in a fuel cell for testing. The test results showed that the doped membranes exhibited good structural stability and efficient energy generation at room temperature, with voltages comparable to commercial materials such as Nafion®. During the temperature tests, distinct behaviors were observed between the membranes with and without additional sulfuric acid doping, suggesting improved thermal stability in the presence of H₂SO₄. However, overall performance remained relatively low, with functionality maintained only up to approximately 150 °C, although with potential for improvement through better system humidification. The characteristics observed suggest that chitosan membranes can be viable and sustainable alternatives for hydrogen fuel cells and may achieve even better results with further additives and modifications to enhance their thermal resistance and proton conductivity. This could contribute significantly to the energy transition using organic and renewable materials. Tipo: Dissertação 2025-01-01T00:00:00Z