Chemical modifications of vegetable oils may be applied for the purpose of improving their physicochemical properties in their usage for the bio‐based lubricants. The vegetable oils with a high percentage of oleic acid, such as soybeans and rapeseed oils, are important raw materials to obtain the biolubricants. In this particular study, the oleic acid was esterified with 1‐octanol, followed by epoxidation. The oxirane ring opening reaction was performed using different alcohol structures (linear, branched, and cyclic), in order to evaluate their influence on the final physicochemical properties with the synthesized samples. These aforesaid reaction steps were followed by 1H nuclear magnetic resonance and the main physicochemical properties in the intermediate and final samples were assessed. The highest oxidative stability was observed for the samples obtained, using a cyclic alcohol at the oxirane ring opening reaction (230 min), followed by the linear alcohols with the branched alcohol presenting the lowest oxidative stability (124 min). The pour point values for the samples synthesized with the branched alcohol were slightly better than those with the linear and cyclic alcohols. All the synthesized samples showed high viscosity indexes (>130) and kinematic viscosities at 40 °C, ranging from 30 to 33 cSt (application degree ISO VG‐32), which are adequate for their use in the formulation of bio‐based lubricants.
The SBA-15 materials were synthesized by the hydrothermal method using tetraethyl orthosilicate as silica source and P123 as template agent. The synthesis process was accomplished varying the time during the hydrothermal processing. For the synthesis monitoring, a small amount of sample was removed at different times, and analyzed by thermal analysis in order to determine the temperature ranges related to water desorption, template decomposition and silanol condensation for the SBA-15 nanostructured materials, as well as to estimate their quality. The samples were characterized by X-ray diffraction, infrared absorption spectroscopy, scanning electron microscopy, BET surface area and pore size distribution. The activation energy relative to decomposition of P123 template was determined from TG curves, using multiple heating rates and applying the model free kinetics. From the obtained data, it is possible to monitor the hydrothermal synthesis of SBA-15 in order to control the properties and conditions to prepare ordered materials.
As metodologias ativas têm sido um meio inovador de construção de conhecimento dos alunos dentro e fora da sala de aula. Entre elas estão a Aprendizagem Baseada em Problemas, Aprendizagem Cooperativa e Sala de Aula Invertida. Tais métodos foram usados de forma associada com métodos investigativos no ensino de Química na Universidade Federal do Ceará Campus Crateús, em uma turma de repetentes. A partir disso, foi analisada a eficácia deste método em comparação à metodologia tradicional de sala de aula. Em adição às avaliações continuadas e formativas realizadas com os alunos, questionários de opinião aplicados pela professora e monitor foram utilizados para obter os dados da pesquisa. Após a aplicação do método híbrido, os alunos foram consultados e os seguintes dados foram observados: 83,3% mostraram-se satisfeitos com seu aprendizado, 93,3% afirmaram ter suas dúvidas sanadas e 60,0% indicaram estar menos pressionados quanto à forma de avaliação. Há ainda que se considerar uma redução de alunos desistentes (4,9%) da disciplina quando comparados com turmas tradicionais. Assim, pode-se inferir que os estudantes apresentam ganhos significativos na compreensão conceitual e competências abordadas pela disciplina de Química.
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