Made available in DSpace on 2015-04-14T13:59:00Z (GMT). No. of bitstreams: 1 450942.pdf: 4010339 bytes, checksum: dc351c22fdec0c4f0d2110191ee28e2f (MD5) Previous issue date: 2013-08-29 / Technological advances that allow reducing the biodiesel production process costs practiced today, are needed to make it more competitive against fossil fuels costs. In this context, the present work studied two methods for the synthesis of biodiesel via enzymatic catalysis using rice bran and the crude oil extracted from it, through the biotransformation of oil in the rice bran and using the lipase found in raw material as biocatalyst. When it was used the molar ratios of methanol:oil 8:1 and hexane:methanol 12:1, 35?C, 180 rpm, 10.5% moisture, 25 g of rice bran for 24 h the reaction with the addition of methanol in two steps has been reached 5.7% conversion to methyl esters. This result demonstrated that the hydrophobic organic solvent with log P > 3 assisted enzymatic catalysis when compared polar solvent (acetronitrile/t-butanol/methanol). The pH adjustment of the medium with the addition of potassium methoxide (1% w/w KOH/oil) under the same reaction conditions increased in 2.2 times conversion to methyl esters (12.9%). The addition of higher concentrations of potassium methoxide (1.5 and 2% w/w) kept the pH ≈ 7, but had no effect on the conversion to methyl esters, unlike promoted a decrease to 10.7% and 7.1%, respectively. The enzymatic catalysis performed on the crude oil extracted from rice bran with molar ratios of methanol:oil 3:1 and hexane:methanol 3:1 using Porcine pancreatic lipase keeping constant the other reaction parameters, led to a 72.1% of conversion to methyl esters. This work showed that, under suitable conditions, the enzyme lipase is more protected from methanol toxicity, while it improves the solubility of the alcohol in the oil thereby promoting the synthesis of biodiesel from rice bran. / Avan?os tecnol?gicos que possibilitem reduzir os custos do processo de produ??o de biodiesel praticados hoje em dia s?o necess?rios, para torn?-lo mais competitivo frente aos combust?veis f?sseis. Neste contexto, o presente trabalho estudou a s?ntese de biodiesel via cat?lise enzim?tica utilizando o farelo de arroz e o ?leo bruto extra?do deste atrav?s da biotransforma??o do ?leo no farelo de arroz e utilizando a lipase presente nesta mat?ria-prima como biocatalisador. Ao se usar as raz?es molares de 8:1 de metanol:?leo e 12:1 de hexano:metanol, 35?C, 180 rpm, 10,5% de umidade, 25 g de farelo de arroz, durante 24 h de rea??o com adi??o de metanol em duas etapas foi alcan?ado 5,7% de convers?o em ?steres met?licos. Este resultado demonstrou que o solvente org?nico hidrof?bico com log P > 3 auxiliou a cat?lise enzim?tica quando comparado com um solvente polar (acetronitrila/t-butanol/metanol). O ajuste de pH do meio com a adi??o de met?xido de pot?ssio (1% m/m KOH/?leo), nas mesmas condi??es reacionais, aumentou em 2,2 vezes a convers?o em ?steres met?licos (12,9%). A adi??o de maiores concentra??es de met?xido de pot?ssio (1,5 e 2% m/m) manteve o pH ≈ 7, mas n?o teve efeito na convers?o em ?steres met?licos, ao contr?rio promoveu uma redu??o para 10,7% e 7,1%, respectivamente. A cat?lise enzim?tica realizada sobre o ?leo bruto extra?do do farelo de arroz nas raz?es molares de 3:1 de metanol:?leo e 3:1 de hexano:metanol utilizando a lipase Porcine pancreas, mantendo-se constante os outros par?metros reacionais, levou a uma convers?o de 72,1% em ?steres met?licos. Este trabalho mostrou que, em condi??es adequadas, a enzima lipase est? mais protegida da toxidade do metanol, ao mesmo tempo em que melhora a solubilidade deste ?lcool no ?leo promovendo assim a s?ntese de biodiesel a partir do farelo de arroz.

Made available in DSpace on 2015-04-14T13:58:56Z (GMT). No. of bitstreams: 1 444965.pdf: 19735321 bytes, checksum: 848931c529752f1baa29108987cfc311 (MD5) Previous issue date: 2012-11-09 / Biodiesel is a synthetic fuel usually produced by the transesterification reaction. This study was undertaken to monitor the kinetics of the transesterification reaction between soybean oil and methanol catalyzed by potassium methoxide. A series of reactions was monitored with a laser spectrometer used to analyze the absorption and scattering of light in real-time. The objectives of this study aimed to determine when the reaction came in chemical equilibrium. This objective was achieved by observing an arbitrary time interval, experimentally obtained from the graph of electrical resistance versus time, allowing optimize reaction time, by using a monitoring system that combined the information received through multiple sensors. Determine if the optical phenomenon observed during the reaction could be described by Euclidean geometry and whether it was related with the internal conical diffraction. It was found that it is not related to the internal conical diffraction, however, depending on the scale applied to observe the optical phenomenon it can be described by the Euclidean geometry. The goal of developing analytical instrumentation was achieved by constructing a non-invasive laser spectrometer. / O biodiesel ? um combust?vel sint?tico, geralmente produzido a partir da rea??o de transesterifica??o. Este trabalho foi desenvolvido para monitorar a cin?tica da rea??o de transesterifica??o entre o ?leo de soja e o metanol, catalisada por met?xido de pot?ssio. Uma s?rie de rea??es foi monitorada com um espectr?metro laser, utilizado para analisar a absor??o e o espalhamento da luz em tempo-real. Os objetivos deste trabalho visaram determinar quando a rea??o entrou em equil?brio qu?mico. Atingiu-se este objetivo atrav?s da observa??o de um intervalo arbitr?rio de tempo, obtido experimentalmente a partir do gr?fico da resist?ncia el?trica em fun??o do tempo, permitindo otimizar o tempo de rea??o atrav?s da utiliza??o de um sistema de monitoramento que combinava as informa??es recebidas atrav?s de v?rios sensores. Determinar se o fen?meno ?ptico observado durante a rea??o poderia ser descrito pela geometria Euclidiana e se o mesmo tinha rela??o com a difra??o c?nica interna. Constatou-se que o mesmo n?o apresenta rela??o com a difra??o c?nica interna, por?m, dependendo da escala utilizada para observar o fen?meno ?ptico, ele pode ser descrito pela geometria Euclidiana. O objetivo de desenvolver instrumenta??o anal?tica foi alcan?ado atrav?s da constru??o de um espectr?metro laser n?o invasivo.

Submitted by Verena Pereira (verenagoncalves@uefs.br) on 2018-07-12T22:04:46Z No. of bitstreams: 1 CESAR ALVES_Disserta??o_Final revisado vera.pdf: 6440316 bytes, checksum: 9325061c1c7981117303732082343992 (MD5) / Made available in DSpace on 2018-07-12T22:04:46Z (GMT). No. of bitstreams: 1 CESAR ALVES_Disserta??o_Final revisado vera.pdf: 6440316 bytes, checksum: 9325061c1c7981117303732082343992 (MD5) Previous issue date: 2018-02-01 / The main objective of this work was to describe the concepts of Atomic Models, within the scenario of the teaching of chemical reactions, relating them empirically to the processes of chemical luminescence and contextualized to the phenomenon of the planetary Auroras. For this purpose, a proposal was presented to help chemistry teachers to provide students with a better understanding of more meaningful learning. The Teaching of Chemistry in Basic Education presents several challenges regarding the introduction of concepts related to the structure of matter. The approach of this project is centered in the interaction between the Astronomy and the Teaching of Chemistry, in an interdisciplinary perspective with focus in the course of didactic engineering. It is premised that this approach may attract the interest of high school students. The methodology was developed in the classrooms of the Luiz Eduardo Magalh?es College in Feira de Santana-BA. The use of a learning sequence, centered on experimental and observational phenomena where the student's performance is intensified by the possibility of self-regulation and confrontation with the proposed situations, enabled an evolution of strategies, enhancing students' cognition. In an enveloping and structured way in its four phases, the course of didactic engineering contributed to progress in improving teaching and learning, since the agreed proposal was executed and indicates that it is possible to favor the learning of concepts of Teaching Chemistry with emphasis to topics, motivating Students to learn / O principal objetivo deste trabalho foi descrever os conceitos de Modelos At?micos, dentro do cen?rio do ensino de rea??es qu?micas, relacionando-os empiricamente com os processos de luminesc?ncia qu?mica e contextualizados com o fen?meno das Auroras planet?rias. Para o efeito, foi apresentada uma proposta para ajudar os professores de qu?mica a oferecer aos alunos uma melhor compreens?o da aprendizagem mais significativa. O Ensino de Qu?mica na Educa??o B?sica apresenta v?rios desafios em rela??o ? introdu??o de conceitos relacionados ? estrutura da mat?ria. A abordagem deste projeto est? centrada na intera??o entre a Astronomia e o Ensino de Qu?mica, em uma perspectiva interdisciplinar com foco no curso da engenharia did?tica. Pretende-se que esta abordagem possa atrair o interesse dos alunos do ensino m?dio. A metodologia foi desenvolvida nas salas de aula do Col?gio Luiz Eduardo Magalh?es em Feira de Santana-BA. O uso de uma seq??ncia de aprendizagem, centrada em fen?menos experimentais e observacionais, onde o desempenho do aluno ? intensificado pela possibilidade de auto-regula??o e confronto com as situa??es propostas, permitiu uma evolu??o das estrat?gias, aprimorando a cogni??o dos estudantes. De forma envolvente e estruturada em suas quatro fases, o curso de engenharia did?tica contribuiu para o progresso na melhoria do ensino e da aprendizagem, uma vez que a proposta acordada foi executada e indica que ? poss?vel favorecer a aprendizagem de conceitos de Qu?mica de Ensino com ?nfase em t?picos, motivando esudantes para aprender