Authors:J. Santos, I. Santos, M. Conceiçăo, S. Porto, M. Trindade, A. Souza, S. Prasad, V. Fernandes, and A. Araújo
Thermoanalytical, kinetic and rheological parameters of commercial edible oils were evaluated. The thermal decomposition of
the oils occurred in three steps, due to polyunsaturated, monounsaturated and saturated fatty acids decomposition, respectively.
According to the temperature of the beginning of the decomposition, the following stability order was observed: corn (A)>corn>sunflower
(A)>rice>soybean>rapeseed (A)>olive>rapeseed>sunflower (A - artificial antioxidants). Kinetic parameters were obtained using
Coats-Redfern and Madhusudanan methods and presented good correlation. According to the activation energy of the first thermal
decomposition event, obtained of Coats-Redfern' method, the following stability order is proposed: sunflower>corn>rice>soybean>rapeseed>olive.
In relation to rheological properties, a Newtonian behavior was observed and no degradation occurred in the temperature range
Authors:M. C. D. Silva, L. M. da Silva, N. A. Santos, M. M. Conceição, A. G. Souza, and A. O. dos Santos
Nowadays the growing fuel deficit requires the development of alternative fuel sources. Biodiesel is a good substitute to the conventional diesel because it is quite similar to the fossil fuel in its main characteristics. However, there are some obstacles, as the properties of cold-flow, to the development of a more useful alternative fuel. In this work we use the X-ray diffraction and differential calorimetry scanning to study low temperature properties of ethylic Babassu biodiesel. Our results show that the nucleation of crystals starts below −8 °C and the crystallization temperature does not change significantly when the sample was submitted to a winterization process. The higher concentrations of ethyl esters from saturated fat acid are probably responsible for this characteristic. The X-ray diffraction, combined with DSC measurements, was efficiently employed in the characterization of cold-flow biodiesel properties, showing to be very helpful techniques.
Authors:J. Botelho, A. Souza, L. Nunes, A. Chagas, I. Garcia dos Santos, M. da Conceição, and P. Dunstan
The standard molar enthalpies of formation of crystalline dialkyldithiocarbamates chelates, [Pd(S2CNR2)2], with R=C2H5, n-C3H7, n-C4H9 and i-C4H9, were determined through reaction-solution calorimetry in acetone, at 298.15 K. From the standard molar enthalpies of formation
of the gaseous chelates, the homolytic (172.43.8, 182.53.2,150.93.1 and 162.63.1 kJ mol−1) and heterolytic (745.03.8, 803.73.3,834.33.1 and 735.23.0 kJ mol−1) mean palladium-sulphur bond-dissociation enthalpies were calculated.
Authors:M. Dantas, A. Almeida, Marta Conceição, V. Fernandes Jr, Iêda Santos, F. Silva, L. Soledade, and A. Souza
This work presents the characterization and the kinetic compensation
effect of corn biodiesel obtained by the methanol and ethanol routes. The
biodiesel was characterized by physico-chemical analyses, gas chromatography,
nuclear magnetic resonance and thermal analysis. The physico-chemical properties
indicated that the biodiesel samples meet the specifications of the Brazilian
National Agency of Petroleum, Natural Gas and Biofuels (ANP) standards. The
analyses by IR and 1H NMR spectroscopy indicated
the ester formation. Gas chromatography indicated that biodiesel was obtained
with an ester content above 97%. The kinetic parameters were determined with
three different heating rates, and it was observed that both the methanol
and ethanol biodiesel obeyed the kinetic compensation effect.
Authors:M. Dantas, Marta Conceição, V. Fernandes Jr, Nataly Santos, R. Rosenhaim, Aldalea Marques, Iêda Santos, and A. Souza
This work evaluates the thermal and kinetic
behaviour of corn biodiesel obtained by the methanol and ethanol routes. As
to the TG curves, in air three thermal decomposition steps are for the methanol
biodiesel and two steps are for the ethanol biodiesel. These steps are related
to the evaporization and/or combustion of the methyl and ethyl esters, respectively.
The corn oil presented four thermal decomposition steps in air, and only one
step in nitrogen. These steps were attributed to the evaporization and/or
decomposition of triglycerides. The TG and DTA profiles of the biodiesel approach
the mineral diesel oil ones.