This thesis aims to investigate the formation of deposits from thermally degraded biodiesel on a hot metal surface under the influence of sodium or copper contaminations. Biodiesel or Fatty Acid Methyl Esters (FAMEs) is a widely utilized biofuel with the potential to replace fossil fuels, however, issues regarding the thermal and oxidative stability prevent the progress of biodiesel for utilization as vehicle fuel. The thermal degradation of biodiesel causes formation of deposits often occurring in the fuel injectors, which could result in reduced engine efficiency, increased emissions and engine wear. However, still have no standard method for evaluation of a fuels’ tendency to form deposits been developed. In this study biodiesel deposits have been formed on aluminum test tubes utilizing a Hot Liquid Process Simulator (HLPS), an instrument based on the principle of the Jet Fuel Thermal Oxidation Tester (JFTOT). Quantitative and qualitative analyses have been made utilizing an array of techniques including Scanning Electron Microscopy (SEM), Gas Chromatography Mass Spectrometry (GCMS) and Attenuated Total Reflectance Fourier Transform Infrared Spectrometry (ATR-FTIR). A multi-factorial trial investigating the effects of sodium hydroxide and copper contaminations at trace levels and the impact of a paraffin inhibitor copolymer additive on three different FAME products, two derived from rapeseed oil and one from waste cooking oil as well as a biodiesel blend with mineral diesel, was conducted.The results exhibited that FAMEs are the major precursor to deposit formation in diesel fuel. The SEM analyses exploited the nature of FAME deposits forming porous structures on hot metal surfaces. Sodium hydroxide proved to participate in the deposit formation by forming carboxylic salts. However, the copper contamination exhibited no enhancing effect on the deposits, possibly due to interference of the blank oil in which copper was received. The paraffin inhibitor functioning as a crystal modifier had significant reducing effect on the deposit formation for all biodiesel samples except for the FAME product derived from waste cooking oil. Further studies are needed in order to investigate the influence of glycerin and water residues to the biodiesel deposit formation. Mechanisms involving oxidative or thermal peroxide formation, polymerization and disintegration have been suggested as degradation pathways for biodiesel. The involvement of oxidation intermediates, peroxides, was confirmed by the experiments performed in this thesis. However, the mechanisms of biodiesel deposit formation are complex and hard to study as the deposits are seemingly insoluble. Nevertheless, ATR-FTIR in combination with JFTOT-processing has potential as standard method for evaluation of deposit forming tendencies of biodiesel.

Submitted by Biblioteca da Faculdade de Farmácia (bff@ndc.uff.br) on 2018-03-05T14:14:06Z No. of bitstreams: 1 JÚLIA GONÇALVES MAYER.pdf: 2883327 bytes, checksum: 6ae955490e1664e27d2c9669ad07a02c (MD5) / Made available in DSpace on 2018-03-05T14:14:06Z (GMT). No. of bitstreams: 1 JÚLIA GONÇALVES MAYER.pdf: 2883327 bytes, checksum: 6ae955490e1664e27d2c9669ad07a02c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os métodos analíticos utilizados para medir o percentual de ácido graxo trans (AGT) em alimentos envolvem cromatografia em fase gasosa com detecção de ionização de chama (CG-DIC), espectrometria de massas (CG-EM) e espectroscopia no infravermelho com transformada de Fourier e refletância total atenuada (FT-IR-ATR). O presente estudo teve como objetivo investigar a viabilidade e a aplicabilidade do uso das técnicas de FT-IR-ATR, sem extração, com extração prévia da gordura e após hidrólise e metilação dos ácidos graxos, para avaliar o conteúdo de AGT em biscoitos recheados e comparar os resultados obtidos com os encontrados para a determinação de ácido elaídico pela técnica de CG-EM. Foram escolhidas 9 marcas de biscoitos recheados sabor chocolate e 1 pacote de gordura vegetal hidrogenada, para ser usada como padrão secundário para análise de AGT por FT-IR-ATR. As amostras foram analisadas, inicialmente, quanto aos seus conteúdos de umidade e lipídeos totais. Para todas as amostras não foi observada concentração de umidade superior a 6,03 g/100 g. Os lipídeos totais variaram de 12,51±0,58 a 23,84±0,09 g/100 g. A presença de AGT foi identificada por FT-IR-ATR pela visualização da banda próxima a 966 cm−1 e confirmada com adição de padrão às amostras. Ao analisar as amostras de biscoito homogeneizadas e sem outro preparo, não foi viável a utilização do método de FT-IR-ATR, visto que a absorção de radiação infravermelha de substâncias da amostra se sobrepõe à absorção na região das ligações duplas trans, o que demonstra que a matriz do alimento pode influenciar na análise. Quanto a presença dos AGT, ácido elaídico (C18:1, n-9 trans) foi identificado e confirmado em todas as amostras através de CG-EM. Ao comparar a quantificação pelos métodos CG-EM e FT-IR-ATR em amostras de extratos e na forma de ácidos graxos metilados (FAME), foram observadas concentrações baixas de ácido elaídico/ácidos graxos trans (de 0,03±0,01 a 0,86±0,01 g/100 g de biscoito) obtidas pelos diferentes métodos. Não foram encontradas diferenças significativas entre as concentrações de AGT determinadas pelos três métodos testados para oito das nove amostras analisadas. O presente trabalho mostrou que a técnica de FT-IR-ATR, analisando o extrato lipídico e as amostras em forma de FAME foi adequado para estimar os teores de AGT em biscoito recheado de chocolate, visto que proporciona uma análise mais rápida, com um menor número de etapas e menor consumo de reagentes em relação às análises por CG-EM / The analytical methods used to measure the percentage of trans fatty acids in foods involve gas chromatography with flame ionization detection (GC-FID), mass spectrometry (GC-MS) and attenuated total reflectance fourier transform infrared spectroscopy (ATR-FT-IR). The aim of the present study was to investigate the feasibility and applicability of ATR-FT-IR techniques, without extraction, with previous extraction of fat and after hydrolysis and methylation of fatty acids to evaluate the content of TFA in filled biscuits, and compare the results obtained with those found for the determination of elaidic acid by the CG-MS technique. Were chosen 9 marks of chocolate filled biscuit and 1 packet of hydrogenated vegetable fat to be used as a secondary standard for AGT analysis by ATR-FT-IR. The samples were initially analyzed for their moisture contents and total lipids. For all samples, no moisture content higher than 6.03 g/100 g. Total lipids ranged from 12.51 ± 0.58 to 23.84 ± 0.09 g/100g. The presence of TFA was identified by ATR-FT-IR through the visualization of the band near 966 cm−1 and confirmed with addition of standard to the samples. When analyzing the homogenized cookie samples and without further preparation, the use of the ATR-FT-IR method was not feasible because the absorption of infrared radiation from sample substances overlaps the absorption in the region of the trans double bonds, which demonstrates that the food matrix may influence the analysis. Regarding the presence of TFA, elaidic acid (C18: 1, n-9 trans) was identified and confirmed in all samples by GC-MS. When comparing quantification by GC-MS and ATR-FT-IR in samples of extracts and in the form of fatty acids methly esters (FAME), low concentrations of elaidic acid / trans fatty acids were observed (0.03 ± 0.01 to 0.86 ± 0.01 g / 100 g of biscuit) obtained by the different methods. No significant differences were found between the concentrations of TFA determined by the three methods tested for eight of the nine samples analyzed. The present study showed that the ATR-FT-IR technique, analyzing the lipid extract and the samples in the form of FAME, was adequate to estimate the TFA contents in chocolate filled biscuit, because it provides a faster analysis with a smaller number of steps and lower toxic chemicals in relation to GC-MS analyzes