Authors:J. Santos, M. Conceiçăo, M. Trindade, A. Araújo, V. Fernandes, and A. Souza
The lanthanidic complexes of general formula Ln(C11H19O2)3 were synthesized and characterized by elementary analysis, infrared absorption espectroscopy, thermogravimetry (TG) and differential
scanning calorimetry (DSC). The reaction of thermal decomposition of complexes has been studied by non-isothermal and isothermal
TG. The thermal decomposition reaction of complexes began in the solid phase for Tb(thd)3, Tm(thd)3 and Yb(thd)3 and in the liquid phase for Er(thd)3 and Lu(thd)3, as it was observed by TG/DTG/DSC superimposed curves. The kinetic model that best adjusted the experimental isothermal thermogravimetric
data was the R1 model. Through the Ozawa method it was possible to find coherent results in the kinetic parameters and according
to the activation energy the following stability order was obtained: Tb(thd)3>Lu(thd)3>Yb(thd)3>Tm(thd)3>Er(thd)3
Authors:M. Souza, Marta Conceição, M. Silva, L. Soledade, and A. Souza
Statins are a group of lipoproteins that
are used in medicine to treat the high cholesterol level. The effectiveness
of statins in reducing the cholesterol level is significant and in long time
scale the reduction of the cholesterol level helps to avoid the incidence
of degenerative diseases. Simvastatin and lovastatin are belonging to the
‘statins’ family, one of the pharmacologic groups used in the
control of dislipidemy. The objective of this work is the thermal stability
and kinetic study of the active forms of simvastatin and lovastatin.
Thermal data indicated that lovastatin and simvastatin are stable up
to 190 and 170°C in air and up to 205 and 203°C in nitrogen, respectively.
For melting temperatures DSC curves showed good correlation with the literature
data. Comparing the activation energies of the statins at heating rate of
10°C min–1, lovastatin is more stable
than simvastatin under the applied experimental conditions.
Authors:F. López, A. Mercê, F. Alguacil, and A. López-Delgado
The thermal behaviour of chitosan was studied by means of thermogravimetry, mass spectrometry and infrared spectrometry. Kinetic
parameters were obtained by advanced kinetic evaluation (differential isoconversional analysis) from DSC curves, in non-isothermal
conditions, at several heating rates, between 5 and 30°C min−1. The results showed that the decomposition of chitosan does not follow a single mechanism because both the activation energy
and the pre-exponential factor are not constant during the course of the reaction. A comparison with the results obtained
by applying different conventional calculating methods is also shown.
Authors:Marta Conceição, V. Fernandes Jr, A. Bezerra, M. Silva, Iêda Santos, F. Silva, and A. Souza
Diesel oil has an important role in the field
of urban traffic as well as in the transportation of products. However, the
amount of the non-renewable sources is continuously decreasing. This fact
and the environmental requirements brought the necessity to search for other,
renewable sources. This paper aimed the dynamic kinetic calculation of thermal
decomposition of castor oil, methanol biodiesel and ethanol biodiesel using
Coats–Redfern, Madhusudanan and Ozawa methods. On the base of the thermogravimetric
curves the following thermal stability order could be established: castor
oil>ethanol biodiesel>methanol biodiesel. Kinetic data presented coherent
results. Methanol biodiesel presented lower activation energy than ethanol
biodiesel, suggesting that methanol biodiesel has a better quality for combustion.
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:J. Santos, Amanda Oliveira, C. Silva, J. Silva, A. Souza, and L. Lima
The kinetic and thermodynamic study of synthetic lubricant oils was
accomplished in this work, using isothermal and non-isothermal thermogravimetry
based on mass loss as a function of time and temperature. The thermodynamic
and kinetic behavior of the synthetic lubricant oils depends on atmosphere
and heating rates used in TG analysis. The kinetic and thermodynamic results
were satisfactory, presenting good correlation.
Authors:S. Galvagno, S. Casu, M. Martino, E. Di Palma, and Sabrina Portofino
The world production of tyre waste amounts to 5106
ton year–1, 2106
tons of which are produced in Europe, but the final destination of nearly
65–70% of them is the landfill, despite the high added value materials
lost and the consequent environmental impact.
to landfilling take into account reconstruction and reuse of the tyres or
the matter and/or energy recovery by means of thermal treatment processes
(incineration, gasification and pyrolysis). Among these, pyrolysis seems to
be a promising and realistic alternative to attain the conversion of tyre
waste into valuable and reusable products.
Present work relates
to experimental tests and results obtained for the study of tyre waste pyrolysis,
conducted by means of thermo-gravimetric analysis (TG) of the material and
the simultaneous determination, through Fourier transform infrared (FTIR)
and mass spectrometry (MS), of the decomposition products. The analysis of
the volatile fraction allows to isolate, within the thermograms, the evolution
of products referable to specific tyre components and therefore it suggests
the application of a multi-component decomposition model. The kinetic model
consequently developed agrees fairly well with the experimental data.
Authors:Chaoyu Zhang, Jisong Zhang, and Guangsheng Luo
Nitration of acetyl guaiacol, one typical aromatic nitration, is highly exothermic and extremely fast. Better control and high efficiency can be achieved in the microreactor due to its enhanced mixing and heat transfer rates. In this study, nitration of acetyl guaiacol was carried out in a microreactor using nitric acid—acetic acid as nitrating agent. The nitration kinetics was first investigated, and a kinetic model was established and revealed good prediction of experimental results at higher temperatures. Effects of molar ratio of nitric acid—acetyl guaiacol, residence time, temperature, and nitric acid concentration on the reaction were studied in detail. Under optimized condition, 90.7% yield of desired product, 5-nitroguaiacol, was achieved with 40% of nitric acid concentration, nitric acid—acetyl guaiacol molar ratio of 2.6, reaction temperature of 120 °C, and residence time of 2 min. Compared to traditional batch reactor, microreactor showed the advantages of higher yield and selectivity, much shorter reaction time, and less use of nitric acid.
The effect of the concentration of benzyl dimethyl amine as a catalyst on the cure reaction of bisphenol-F based epoxy resin(BPF)/nadic
methyl ahydride(NMA) system was studied by differential scanning calorimetery using an isothermal approach over the temperature
range 115-145C. Kinetic parameters of the curing reaction including the reaction order, activation energy and kinetic rate
constants were investigated. The results were dependent on the cure temperature and catalyst concentration and proceeded through
an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained by the Arrhenius
kinetic model. The suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetic
of BPF resin compositions as a function of the catalyst content and temperature.
Authors:X. Wang, X. Li, H. Yan, Y. Qu, G. Sun, X. Xie, and Y. Zhang
The kinetic characteristic of thermal decomposition of the Emulsion Explosive Base Containing Fe and Mn elements (EEBCFM)
which was used to prepare nano-MnFe2O4 particles via detonation method was investigated by means of non-isothermal DSC and TG methods at various heating rates of
2.5, 5 and 7.5°C min−1respectively under the atmosphere of dynamic air from room temperature to 400°C.
The results indicated that the EEBCFM was sensitive to temperature, especially to heating rate and could decompose at the
temperature up to 60°C. The maximum speed of decomposition (dα/dT)m at the heating rate of 5 and 7.5°C min−1 was more than 10 times of that at 2.5°C min−1 and nearly 10 times of that of the second-category coal mine permitted commercial emulsion explosive (SCPCEE). The plenty
of metal ions could seriously reduce the thermal stability of emulsion explosive, and the decomposition reaction in the conversion
degree range of 0.0∼0.6 was most probably controlled by nucleation and growth mechanism and the mechanism function could be
described with Avrami-Erofeev equation with n=2. When the fractional extent of reaction α>0.6, the combustion of oil phase primarily controlled the decomposition reaction.