Authors:S. Silva, M. Conceiçăo, A. Souza, S. Prasad, M. Silva, V. Fernandes, A. Araújo, and F. Sinfrônio
The powder and the bran of algaroba pods, submitted to drying temperatures of 55, 65, 75, 85, 95 and 105C, were studied by
conventional and thermogravimetric methods. The dynamic thermogravimetric curves of the samples indicated the following thermal
stability order: 105>55>65>95>85>75C. The powder and the bran of algaroba pods, dried at 55C, presented protein content
higher and isothermal thermogravimetric profiles comparable. The calorimetric curves of samples, dried at 55C, indicated
the gelatinization of starch.
Authors:Anne Garrido Pedrosa, M. Souza, A. Silva, Dulce Melo, and A. Araujo
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.
Authors:A. Silva, M. Souza, J. Aquino, V. Fernandes Jr, and A. Araujo
In this work was studied the acid properties of a series of HZSM-12 zeolites with different Si/Al molar ratio. The samples
of ZSM-12 were synthesized by the hydrothermal method starting from a gel with the following molar composition: 20MTEA:10Na2O:xAl2O3:100SiO2:200H2O, where: x=2, 1, 0.67 and 0.50, respectively. After the synthesis, the samples of ZSM-12 were ion-exchanged NH4Cl solution to obtain zeolite in the acid form (HZSM-12). The acid properties were evaluated by n-butylamine thermodesorption in a TG equipment at three different heating rates. The model-free kinetic model was applied
in the TG integral curves to estimate the apparent activation energy (Ea) of the n-butylamine desorption process. The results obtained showed that the HZSM-12 zeolite presents two kinds main of
acid sites: one with Ea in the range of 115-125 kJ mol-1 classified as weak and other kind with Ea varying of 230-250 kJ mol-1 classified as strong.
Authors:J. Regis Botelho, A. Duarte Gondim, I. Garcia dos Santos, P. Dunstan, A. Souza, V. Fernandes, and A. Araújo
The standard molar enthalpy of formation of crystalline dialkyldithiocarbamate chelates, [Pd(S2CNR2)2], with R=CH3 and i-C3H7, was determined through reaction-solution calorimetry in 1,2-dichloroethane, at 298 K. Using the standard molar enthalpies
of formation of the gaseous chelates, the homolytic (52618 and 66610) and heterolytic (269318 and 295710 kJ mol-1) mean enthalpies of palladium-sulphur bond dissociation were calculated.
Authors:Frederico A. D. Araújo, Sonia V. Pereira, Deivson C. S. Sales, A. R. Schuler, and Cesar A. M. Abreu
The free fatty acids of cotton seed oil were processed with methanol and ethanol into the corresponding alkyl fatty esters in the presence of diluted sulfuric acid. The products characterized as biodiesels presented higher mass fraction levels (43.0 wt%) of the alkyl linoleates, and 17.0 and 13.0 wt% of the alkyl esters C16:0 and C18:1, respectively. A model based on the mechanism of the acid esterification, and representing the evolutions of the fatty ester concentrations, was fitted to the experimental evolution results where the orders of magnitude of the kinetic parameters were quantified. The selectivities of the methyl and ethyl fatty esters in the biodiesel mixtures were compared, where the C18:2 ethyl linoleate selectivity (92.3 %) in the ethyl biodiesel was almost twice the methyl linoleate selectivity (57.3 %) in the methyl biodiesel.
Authors:M. Brito, Gabriela Barin, A. Araújo, D. de Sousa, S. Cavalcanti, Ana Lira, and Rogéria Nunes
The aim of this work was to study the effect of Lippia sidoides essential oil (LSEO) on stratum corneum lipids and the permeation of salicylic acid. DSC and FTIR spectroscopy were applied.
LSEO 1% (v/v) significantly enhanced salicylic acid flux through snake skin. According to the DSC curves changes in the transition
temperature of the lipids were observed indicating that LSEO can interact with stratum corneum. The IR spectrum of skin treated
with LSEO showed a decrease in the peak intensity for CH2 stretchings (2920–2850 cm–1) however the peak positions did not alter suggesting the extraction of the lipids.
Authors:E. Araújo, Renata Barbosa, Amanda Oliveira, Crislene Morais, T. deMélo, and A. Souza
Polyethylene/montmorillonite clay nanocomposites were obtained via direct
melt intercalation. The clay was organically modified with four different
types of quaternary ammonium salts. The objective of this work is to study
the use of montmorillonite clay in the production of nanocomposites by means
on rheological, mechanical and crystallization properties of nanocomposites
and to compare to the properties of the matrix and PE/unmodified clay nanocomposites.
In general, the tensile test showed that the yield strength and modulus of
the nanocomposites are close to the pure PE. Apparently, the mixture with
Dodigen salt seems to be more stable than the pure PE and PE/unmodified clay.
Authors:H. Polli, L. Pontes, M. Souza, V. Fernandes Jr, and A. Araujo
The degradation kinetics
of polycarbonate with flame retardant additive was investigated by means of
thermogravimetric analysis. The samples were heated from 30 to 900C in
nitrogen atmosphere, with three different heating rates: 5, 10 and 20C
min–1. The Vyazovkin model-free kinetics
method was applied to calculate the activation energy (Ea)
of the degradation process as a function of conversion and temperature. The
results indicated that the polycarbonate without flame retardant additive
starts to loose mass slightly over 380C and the polycarbonate with flame
retardant additive, slightly over 390C (with heating rate of 5C
min–1). The activation energy for flame retardant
polycarbonate and normal polycarbonate were 190 and 165 kJ mol–1,
Authors:E. Araújo, Renata Barbosa, Crislene Morais, L. Soledade, A. Souza, and Moema Vieira
Nanocomposites containing both polyethylene and montmorillonite clay organically modified with four different types of quaternary
ammonium salts were obtained via direct melt intercalation. Thus, the main purpose of this work was to evaluate the effect
of the organoclay on the thermal stability of polyethylene. The organoclays were characterized by XRD, FTIR, DSC and TG. The
polyethylene/organoclay nanocomposites were studied by XRD, TEM, TG, besides an evaluation of their mechanical properties.
The results showed that the salts were incorporated by intercalation between the layers of the organoclay and, apparently
that the nanocomposites were more thermally stable than pure polyethylene.