Authors:C. Santos, B. Capistrano, F. Vieira, M. Santos, S. Lima, E. Longo, C. Paskocimas, A. Souza, L. Soledade and I. Santos
In this work, spinels with the general formula Zn2−xCoxTiO4 were synthesized by the polymeric precursor method and thermally treated at 1,000 °C. The powder precursors were characterized
by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations
were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of
the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn2TiO4 after thermal treatment at 500 °C, which disappeared after cobalt addition, indicating that organic material elimination
Authors:O. S. Monteiro, A. G. Souza, L. E. B. Soledade, N. Queiroz, A. L. Souza, V. E. Mouchrek Filho and A. F. F. Vasconcelos
The vegetal species Pimenta dioica Lindl, popularly known as Jamaican pepper, is a 6–15 m tall tree, which belongs to the Mirtaceae family. Its fruits have an essential oil of great economic value in the international market, due to its high level of eugenol (its major compound), which is largely used in chemical and pharmaceutical industries. In this work, the extraction of the essential oil from the fruits of Pimenta dioica Lindl was carried out by the hydrodistillation method, using a modified Clevenger system. It was observed that the volume of the extracted oil reaches a maximum at 4 h, with a yield of 2.7% (m/m). The essential oil was characterized by physico-chemical analyses, such as density, refraction index, ethanol solubility, color, and appearance, besides UV–vis and infrared spectroscopy and gas chromatography/mass spectrometry. Thus, eugenol was confirmed as the major component of the essential oil of Pimenta dioica Lindl (77%). The technique of differential scanning calorimetry (DSC) was used for the determination of boiling point of the sample of essential oil from the fruits of Pimenta dioica (L.).
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
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.
Authors:K. L. G. V. Araújo, P. S. Epaminondas, M. C. D. Silva, A. E. A. de Lima, R. Rosenhaim, A. S. Maia, L. E. B. Soledade, A. L. Souza, I. M. G. Santos, A. G. Souza and N. Queiroz
Physicochemical and thermal analyses were undertaken to evaluate the influence of the temperature on the oxidation of sea fish oil once its polyunsaturated fatty acids deteriorate rapidly. Fish oil displayed four decomposition steps in synthetic air atmosphere and only one step in nitrogen atmosphere. The first step started at 189 and 222 °C for oxidizing and inert atmospheres, respectively. An OIT value of 53 min was measured at 100 °C. After the degradation process the peroxide index and the iodine index reduced from 35.38 to 9.85 meq × 1000 g−1 and from 139.79 to 120.19 gI2 × 100 g−1, respectively. An increase of the free fatty acids amount from 0.07 to 0.17% was observed while viscosity increased from 57.2 to 58.0 cP. Absorption at 272 nm also increased. The thermogravimetric and spectroscopic techniques are reproducible and versatile being an option for characterization of edible oil oxidation.