Authors:Bruno Souza, Ana Moreira, and Ana Teixeira
Thermogravimetry has been widely used for the characterization of several biomasses but the most useful information given
by this technique has been normally concerned to the relative amounts of humidity, hemi-cellulose, cellulose and lignin present
in the biomass. TG-FTIR has been used to yield qualitative data about the pyrolysis products, in an exploratory way, by some
authors. In the present paper, this technique was employed to reach comparative data about the products of pyrolysis of biomasses
that are potentially available at economic bases for the production of biofuels. Agricultural residues such as coconut shell,
sugarcane bagasse, corn stalks and peanut shell were chosen to be investigated. For all samples, the thermogravimetric curves
showed a mass loss between 35 and 400 °C changed up to 73%, while that the loss between 400 and 800 °C changed up to 26%.
TG-FTIR indicated tendencies in the rate of the formation of important species during the pyrolysis process of the four biomasses
studied. The interpretation of the spectra allowed the proposition of characteristic absorbance ratios and the comparison
of these values allowed inferences about the relative abundances of components formed in the pyrolysis of the biomasses. As
an example of the possible inferences reached, among the species formed in the pyrolysis condensate, called bio-oil, the formation
of carboxylic acids has to be specially considered due to their corrosivity. Thus, the data produced indicated that a bio-oil
derived from peanut shell should be a little less acidic while the one derived from sugarcane bagasse should be showed more
acidic among the biomasses studied.
Authors:Ana Moreira, Bruno Souza, and Ana Teixeira
Naphthenates are produced when naphthenic acids present in crude oil are mixed with brine. They deposit at oil/water interface
and are insoluble in either of the phases causing a large problem to the oil industry. Generally, naphthenates precipitate
jointly with others compounds such as sulfates and carbonates. This fact makes difficult their characterization. In this study,
calcium stearate formation from stearic acid was investigated, under different conditions, as a previous model to understanding
of calcium naphthenate precipitation. Medium reactions distinct were studied and the results indicated that the ethanol medium
was the most efficient for the formation of solids because in this only case, the stearic acid was completely converted into
stearate. Monitoring of the conversion was performed by thermogravimetry in spite of this technique not be typical in salts
characterization. Nevertheless, the thermogravimetric analysis showed that is possible to identify differences between an
organic acid, a salt of this acid and an inorganic salt, in the same sample. Infrared spectra was used in order to confirm
the results obtained by thermogravimetry. However, this technique showed less efficiency and sensibility.
Authors:Maria Gonçalves, Deusa da Mota Pinto, Ana Teixeira, and M. Teixeira
Dynamic kinetic analyses were performed on different Brazilian petroleum fractions by thermogravimetry. The data were treated
by a multiple heating rate methodology. The apparent activation energies for the light and middle fractions within the range
of 62–74 kJ mol−1 and for heavy distillation residues were within the range of 80–100 kJ mol−1 at lower conversions and 100–240 kJ mol−1 at higher conversions. The kinetic study can be a criterion for tells apart the main phenomena involved in the thermal behavior
of the refinery feedstock.
Authors:Maria Gonçalves, Méri Vieira, Wildson Cerqueira, and Ana Teixeira
The purpose of this work was to employ the differential thermal analysis technique (DTA) to compare variations in the collapse
energy of the Y zeolite crystalline structure in a fresh sample and in the sample after temperature treatment and impregnated
with 3,000 ppm of vanadium and nickel. A small exothermic signal in the DTA curve at 950–1,150 °C indicated the collapse of
the crystalline structure. The areas of the exothermic signals in the DTA curves of the samples indicated a 20% reduction
in the exothermic area peak of sample treated 600 °C for 3 h and 25% reduction in same peak in the metal impregnated Y zeolite.
These results were compared with X-ray data leading to the conclusion that metal impregnation affects the Y zeolite crystalline
structure and that the DTA technique is a potentially useful tool for measuring the integrity of Y zeolite in catalysts.
Authors:Maria Gonçalves, Joyce Barreto, Wildson Cerqueira, and Ana Teixeira
This work evaluates the effect of the FCC catalyst components—Y zeolite, kaolin and alumina—on the formation of coke during
the cracking of heavy residue (HR) of petroleum. The Y zeolite, kaolin and alumina were mixed with a HR at a ratio of approximately
1:4. The effect was studied using dynamic thermogravimetry at a heating rate of 50 K min−1, with N2 (between 35 and 700 °C) and air (in the 700–1,000 °C temperature range). The HR analyzed in these conditions formed 8.1%
of coke. All the mixtures presented larger coke formation than that observed in pure HR. The Y zeolite presented fourfold
larger coke formation, while kaolin and alumina showed twofold higher formation than pure HR. The major focus of this study
was to verify the sensitivity of the TG technique in providing information about coke formation in the fluid catalytic process
Authors:Maria Gonçalves, Meri Vieira, Deusa Mota, Wildson Cerqueira, and Ana Teixeira
The purpose of this work was to employ the differential thermal analysis (DTA) technique to compare variations in the collapse
energy of the zeolite Y crystalline structure in a fresh catalyst and in the same catalyst impregnated with nickel and vanadium.
A small exothermic signal in the DTA curve at 950–1150 °C indicated the collapse of the crystalline structure. The areas of
the exothermic signals in the DTA curves of the two samples indicated a reduction in the curve of the metal impregnated catalyst.
These results were compared with X-ray data, leading to the conclusion that metal impregnation affects the zeolite Y crystalline
structure and that the DTA technique is a potentially useful tool for measuring the integrity of zeolite Y in catalysts.
Authors:Maria Luisa A. Gonçalves, Deusa A. Pinto da Mota, Ana Maria R. F. Teixeira, and M. A. G. Teixeira
Summary Thermogravimetry (TG) is a potential tool to evaluate petroleum distillation residues, obtained in the crude oil distillation. Analyses were done at different heating rates, mass samples and gas flow rates. No differences were observed in the yields of the products formed during the pyrolysis at different analytical conditions. Linear correlation was found between the results of the TG and the standard methods for the prediction of the light fraction rates given by the pyrolysis.
Authors:Maria Luisa A. Gonçalves, D. A. Ribeiro, Deusa Angélica P. Da Mota, Ana Maria R. F. Teixeira, and M. A. G. Teixeira
Summary Thermogravimetry (TG) was applied to evaluate the thermal behavior of five refinery atmospheric distillation residues (ATR) obtained from different Brazilian crude oils. The asphaltenes were extracted of each sample and their influence on coke formation was studied. It was observed that they have a great contribution on carbonaceous residues formation during pyrolysis and that the heavier the ATR sample, the higher is the contribution of other heavy components present in ATR samples.