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Journal of Thermal Analysis and Calorimetry
Authors: A. Souza, H. Danta, M. Silva, I. Santos, V. Fernandes, F. Sinfrônio, L. Teixeira, and Cs. Novák

Abstract  

The biodiesel obtained by transesterification by reaction between ester and an alcohol in the presence of catalyst. The purpose of this work is to evaluate the thermal and kinetic behavior of the methanol biodiesel derived from cotton oil. The quality analysis was done by gas chromatography and proton nuclear magnetic resonance spectrometry (1H NMR) in order to examine if the product meets with the requirements of the European Standard EN 1403. The thermogravimetric profile of the cotton biodiesel indicated that the decomposition steps are associated to the volatilization and/or decomposition of the methyl esters. Kinetic data was also obtained by thermal analysis.

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Journal of Thermal Analysis and Calorimetry
Authors: H. Dantas, R. Mendes, R. Pinho, L. Soledade, C. Paskocimas, B. Lira, M. Schwartz, A. Souza, and Iêda Santos

Abstract  

Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4⋅2H2O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase transformation is observed associated to the loss of water, leading to the formation of gypsum or anhydrite, which may present different phases. The identification of the phases is not so easy since their infrared spectra and their X-ray diffraction patterns are quite similar. Thus, in this work, temperature modulated differential scanning calorimetry (TMDSC) was used to identify the different gypsum phases, which can be recognized by their different profiles.

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Journal of Thermal Analysis and Calorimetry
Authors: N. A. Santos, R. Rosenhaim, M. B. Dantas, T. C. Bicudo, E. H. S. Cavalcanti, A. K. Barro, I. M. G. Santos, and A. G. Souza

Abstract

Biodiesel is an increasingly attractive alternative to diesel fuel. The main component of Babassu biodiesel is lauric acid (C12:0), which is a saturated fatty acid with a high melting point. Controlling flow properties, such as viscosity and the cold filter plugging point, is critical because viscosity affects atomization, and crystal formation resulting from decreases in temperature can negatively affect engine starting and performance. To evaluate its flow characteristics more fully, the rheological properties of babassu biodiesel were analyzed, taking into account variations in temperature. The crystallization temperature was determined by modulated temperature differential scanning calorimetry (MT-DSC). The curve of biodiesel viscosity as a function of the biodiesel refrigeration temperature contained an inflection point (corresponding to a steep increase in viscosity) that was coincident with both the transition from a Newtonian-type flow to a pseudoplastic-type flow and the crystallization temperature obtained by MT-DSC, indicating that the appearance of crystals in the biodiesel increased its viscosity. The rheological properties of fatty acid methyl and ethyl mixtures (FAME and FAEE) with metropolitan diesel were also evaluated; a higher FAME percentage reduced viscosity in blends up to B100.

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Biodiesel from soybean oil, castor oil and their blends

Oxidative stability by PDSC and rancimat

Journal of Thermal Analysis and Calorimetry
Authors: M. B. Dantas, A. R. Albuquerque, L. E. B. Soledade, N. Queiroz, A. S. Maia, I. M. G. Santos, A. L. Souza, E. H. S. Cavalcanti, A. K. Barro, and A. G. Souza

Abstract

Even not being described in the EN 14112 standard, PDSC has been used for the determination of the biodiesel oxidative stability, by OIT and OT measurements. In this study, biodiesel blends were obtained by mixing soybean (BES) and castor (BEM) ethyl esters and its induction periods were measured by Rancimat and PDSC. The blends (BSMX) showed intermediate values of OSI, OT, and OIT, compared with BES and BEM. Although, the molar fraction of the components varied linearly in BSMX, OSI, OT, and OIT values increased exponentially in relation to the castor biodiesel amount in the blends. Introduction of castor oil biodiesel increased the blend stability, so the BSM30 blend reached the OSI limit of 6 h. OSI, OIT, and OT showed a high-linear correlation, pointing out that PDSC can be used in the analysis of this kind of biodiesel, with a smaller sample and analysis time, as compared to Rancimat. The use of biodiesel blends was a good alternative in the correction of the oxidative stability of the final product without the need of antioxidant addition.

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