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- (In)formação sobre pictogramas de substâncias perigosas: (re)conhecer impactes no ambiente e na saúdePublication . Monteiro, Silvia; Heleno, Lizete; Sebastião, Fernando; Ispolnov, Kirill; Santos, OlgaConsiderando que o conhecimento dos pictogramas de substâncias perigosas é fundamental para promover atitudes que minimizem impactes no ambiente e na saúde, foi levado a cabo o trabalho que aqui se apresenta, alicerçado nos seguintes objetivos: i) avaliar o nível de perceção dos estudantes de Cursos Técnicos Superiores Profissionais de uma instituição do ensino superior sobre os pictogramas de substâncias perigosas, definidos pelo GHS, ii) compreender de que modo a estratégia formativa trabalhada com os estudantes contribuiu para a mudança conceptual sobre a interpretação dos pictogramas de substância perigosas e iii) realçar a importância do conhecimento dos pictogramas de substâncias perigosas de forma a minimizar o potencial de ocorrência de acidentes ambientais, acidentes de trabalho e de doenças profissionais. Foi analisada a compreensão destes pictogramas por parte de 669 estudantes, antes e após formação sobre o tema. A análise dos dados por pictograma em função da área de formação, idade e estatuto de trabalhador estudante ou não, foi efetuada com ferramentas de estatística descritiva e através de testes de hipóteses. Em média, o nível de compreensão correto dos pictogramas após a formação (61.19%) foi superior ao observado antes da formação (30.75%). A formação em risco químico é essencial para melhorar o nível de compreensão dos respetivos pictogramas, e deverá ser valorizada e incluída nos currículos escolares desde a escolaridade obrigatória até ao ensino superior.
- Biodiesel Density: Experimental Measurements and Prediction ModelsPublication . Pratas, Maria Jorge; Freitas, Samuel V. D.; Oliveira, Mariana B.; Monteiro, Silvia; Lima, Álvaro S.; Coutinho, João A. P.Density is an important biodiesel parameter, with impact on fuel quality. Predicting density is of high relevance for a correct formulation of an adequate blend of raw materials that optimize the cost of biodiesel fuel production while allowing the produced fuel to meet the required quality standards. The aim of this work is to present new density data for different biodiesels and use the reported data to evaluate the predictive capability of models previously proposed to predict biodiesel or fatty acid methyl ester densities. Densities were measured here for 10 biodiesel samples, for which detailed composition is reported, at atmospheric pressure and temperatures from 278.15 to 373.15 K. Density dependence with temperature correlations was proposed for the biodiesels, and isobaric expansivities are presented. The new experimental data presented here were used along with other literature data to evaluate predictive density models, such as those based on Kay’s mixing rules and the GCVOL group contribution method. It is shown that Kay’s mixing rules and a revised form of the GCVOL model are able to predict biodiesel densities with average deviations of only 0.3%. A comparison between biodiesel densities produced from similar vegetable oils, by different authors, highlights the importance of knowing the detailed composition of the samples. An extension of GCVOL for high pressures is also proposed here. It is shown that it can predict the densities of biodiesel fuels with average deviations less than 0.4%.
- Densities and Viscosities of Minority Fatty Acid Methyl and Ethyl Esters Present in BiodieselPublication . Pratas, Maria Jorge; Freitas, Samuel; Oliveira, Mariana B.; Monteiro, Silvia; Lima, Álvaro S.; Coutinho, João A.P.Biodiesels have several known components in their composition. The majority of components is well described in the literature, but a minority of components are poorly characterized. These are however required to develop reliable models to predict the biodiesel behavior. This work considers minor components of biodiesel: the polyunsaturated compounds (in C18), the monounsaturated (in C16, C20, and C22), and the long-chain saturated esters. In this work, densities and viscosities of pure fatty acid ester minor components of biodiesel fuel were measured (three ethyl esters and seven methyl esters), at atmospheric pressure and temperatures from (273.15 to 373.15) K. Correlations for the densities and viscosities with temperature are proposed. Three predictive models were evaluated in the prediction of densities and viscosities of the pure ethyl and methyl esters here reported. The GCVOL group contribution method is shown to be able to predict densities for these compounds within 1.5 %. The methods of Ceriani et al. (CM) and of Marrero et al. (MG) were applied to the viscosity data. The first show a better predictive capacity to provide a fair description of the viscosities of the minority esters here studied.
- Densities and Viscosities of Fatty Acid Methyl and Ethyl EstersPublication . Pratas, Maria Jorge; Freitas, Samuel; Oliveira, Mariana B.; Monteiro, Sílvia C.; Lima, Alvaro S.; Coutinho, João A. P.To develop reliable models for the densities and viscosities of biodiesel fuel, reliable data for the pure fatty acid esters are required. Densities and viscosities were measured for seven ethyl esters and eight methyl esters, at atmospheric pressure and temperatures from (273.15 to 363.15) K. A critical assessment of the measured data against the data previously available in the literature was carried out. It is shown that the data here reported presents deviations of less than 0.15 % for densities and less than 5 % for viscosities. Correlations for the densities and viscosities with temperature are proposed. The densities and viscosities of the pure ethyl and methyl esters here reported were used to evaluate three predictive models. The GCVOL group contribution method is shown to be able to predict densities for these compounds within 1 %. The methods of Ceriani and Meirelles (CM) and of Marreiro and Gani (MG) were applied to the viscosity data. It is shown that only the first of these methods is able to provide a fair description of the viscosities of fatty acid esters.