Thermogravimetric data were used to calculate the kinetics of isothermal degradation of layered tetratitanate intercalated
with n-alkyldiamines H2N(CH2)nNH2 (n=2, 3, 4, 6 or 8). The hydrous matrix showed two mass loss steps from the thermogravimetric curve, corresponding to the release
of physisorbed and lattice water molecules. For the intercalated matrices a third mass loss was observed due to the release
of organic moiety. From these values, the amine intercalated matrices can be ordered in the following sequence of thermal
stability; C4>C2>C3≅C6>C8. Kinetic studies were carried out to the release of lattice water molecules. The kinetic model that
best adjusted the experimental isothermal TG data was the diffusion mechanism controlling process.
Thermogravimetric data and the kinetic interpretation of the curves of mass loss for ferrocene, ferrocenecarboxylic and ferrocenedicarboxylic
acids and a series of ferrocene-containing polyamides are presented. The results indicate that the degradation process occurred
with more than one stage of thermal degradation. The apparent activation energy values and the FTIR spectra of the degradation
products suggest that the degradation mechanism occurred by either scission of weak links or by random scission of the chain.
Apparently, the N-vicinal methylene group was the primary site of attack of oxygen on the polymer chain.
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.
bifunctional catalysts were synthesized using impregnation and polymeric precursor
methods. After the synthesis process the samples were calcined at 600, 700
and 800C and characterized by X-ray diffraction, nitrogen adsorption
and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles
showed between three and five reduction events at different temperatures attributed
to platinum reduction and to different stages of tungsten species reduction.
A comparative study of the synthesis method influence on the DTG-TPR curves
The thermal degradation process of mineral base lubricating oils was
studied in this work by means of thermal, spectroscopic and rheologic analysis.
The lubricating oils were degraded at temperatures varying from 150 to 210C,
and for degradation times from 1 to 48 h. After the degradation, the lubricating
oils were characterized by X-ray fluorescence, IR and NMR spectroscopies,
rheological properties and thermal analyses (TG/DSC). The spectroscopic analyses
determined the oxidation reaction products. TG curves indicate that the thermal
stability of lubricating oils is below 161C. TG curves in air present
three mass loss stages, whereas in nitrogen there are only two mass loss steps.
DSC analyses in air indicate two highly exothermic peaks related to hydrocarbon
oxidation and combustion processes, while in nitrogen only two endothermic
peaks were observed. The decrease in the degradation temperature led to a
decrease of the lubricant viscosity.
Seismic coda Qattenuation (Qc) in the frequency range from 6 to 20 Hz of two distinct Scoda windows (early and later portions) are compared to analyse the effects of both coda windows on crustal seismic attenuation estimates around Samambaia fault (João CâmaraNortheastern Brazil). Qcvalues associated with the later portion are systematically higher than those related to the early portion. These values follow a frequency (f) function given by Qc(f) = Q0f, where Q0= 11739 and= 1.000.06. In general, Q0estimate is less sensitive to site effects and stabler than that obtained from the early portion of S coda waves, while its corresponding frequency dependence is similar to that obtained from the early portion of S coda waves. It suggests thatparameter does not depend on coda window's location along the seismic signal. A comparative analysis of both Q0andvalues with those found recently shows that there is no difference in using early or later portion of S coda waves in the stations located on Pre-Cambrian basement in the João Câmara area. This comparison also shows that the major variations in Q0values were observed at seismic stations installed on sedimentary terrain. Differences in the seismic attenuation, in both sides of the Samambaia fault, were also observed in this study, and it is in agreement with the hypothesis that Samambaia fault is a kind of boundary between two seismic attenuation zones.
The study of the incorporation
of rare earth elements as additives in Y zeolites is a very interesting field
of research, mainly by its potential application as additives in catalytic
cracking process. In this work was studied the thermal and structural properties
of cerium, holmium and samarium supported on HZSM-12 zeolite. The obtained
materials were characterized by X-ray diffraction (XRD), infrared spectroscopy
(FTIR), nitrogen adsorption, thermogravimetry (TG/DTG), differential scanning
calorimetry (DSC) and differential thermal analysis (DTA). TG/DSC/DTA analyses
showed that the dehydration temperatures of RE/HZSM-12 zeolites (RE=Ce, Ho, Sm) increase in relation to pure HZSM-12.
The acid properties were investigated by pyridine thermo desorption via TG.
The results showed two events of mass loss attributed to elimination of pyridine
adsorbed on the weak+medium acid sites and on the strong acid sites.
This work present comparative results on powder milk storage quality, obtained from analytical methods. Protein content was
determined conventional (Kjeldahl) and colorimetric with biuret reagent at 540 nm and integral quality by thermogravimetric
and biological methods. A method was developed for the protein separation of powder milk. Powder milk was submitted to degradation
processes at 45, 60 and 80°C for 20 days. The results indicated that protein content values were inconsistent if determinations
by Kjeldahl and colorimetric methods and biological tests were compared. There is evidence of thermal decomposition of powder
milk as detected by biological and thermogravimetric methods.
The thermogravimetric procedures applied to quality control of foods attain the global analysis of quality of the product,
through the determination of quality parameters and the thermal stability of products. The kinetic parameters such as order
of reaction, apparent activation energy, pre-exponential factors and the thermal decomposition rate constant were determined
for the samples of corn and its derivatives by applying isothermal thermogravimetry, utilizing the Arrhenius law. This method
presented excellent results as verified with the coherence and data adjustment. The rate constant values showed the expected
performance from the chemical point of view.