A thermogravimetric method is proposed for study of the kinetic parameters of coked HZSM-5 zeolite regeneration. The technique,
which makes use of integral thermogravimetric curves, was optimized by microprocessed integrated mathematical methods. The
kinetic parameters obtained from the TG curves are the activation energy, the rate constants, the half-life times, and in
particular the coke removal time as a function of temperature. The activation energy calculated by using the Flynn and Wall
kinetic method was 81.4 kJ mol−1. It was observed that, to remove 99% of the coke from the zeolite in a period of 1 h, it would be necessary to carry out
thermo-oxidation at 748 K, with a dry air purge flow of 120 cm3 min−1.
The spatial distribution of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) was analysed in ornamental crops (roses and spray-type carnations) and horticultural crops (pepper and strawberries), inside greenhouses, using sticky traps. In ornamental crops, at low population densities, during the winter, there was not a constant location of the isolated foci of infestation, from one week to the next, or a specific pattern of variation in that location. In spray-type carnations, pepper and strawberries, at higher population densities, in spring and summer, the basic units of distribution were the individuals, and they were aggregated. For roses, at those population levels, a random distribution was observed, with a tendency for aggregation. The number of traps needed to estimate population densities, in each crop, was evaluated for two fixed levels of precision (0.10 and 0.25) and results are indicated and discussed.
Authors:A. Silva, M. Souza, J. Aquino, V. Fernandes, and A. Araújo
The coke removal of HZSM-12 zeolite deactivated in the reaction of n-heptane cracking was studied by thermogravimetry using
two multiple heating rate integral kinetics models proposed by Ozawa-Flynn-Wall and Vyazovkin to obtain the activation energy
of process of thermoxidation of coke. The results obtained by both models presented excellent accordance with the related
Authors:A. Araujo, V. Fernandes, A. Silva, and J. Diniz
The evaluation of the crystallinity of several samples of ALPO-11 was performed by X-ray diffraction and thermogravimetry.
Through XRD, the degrees of crystallinity of the samples were determined by the measurement of the area of the peaks at 2γ
ranging from 20.7 to 24.1 degrees. The sample that presented the largest area was considered as 100% crystalline and the areas
of the other samples were normalized in relation to this. From TG, the degree of crystallinity was determined considering
the mass loss in the temperature range from 453 to 653 K that is related to remotion of di-isopropylamine molecules used during
the synthesis procedure. The quantity of diisopropylamine on the material is proportional to the degree of crystallinity.
Authors:C. Corredeira, M. Araújo, A. Gouveia, and J.-M. Jouanneau
A geochemical study was carried out in sediment cores along the Galician Continental Shelf and at the mouth of the Vigo and
Pontevedra Rias. Multielemental analysis was performed by Instrumental Neutron Activation Analysis and Energy Dispersive X-ray
Fluorescence Spectrometry. Sedimentological and geochemical characterisation (lithogenic, biogenic and anthropogenic elements)
indicates different supplies for the fine-grained, deposited sediments. No significant heavy metal enrichment could be detected
in coastal sediments despite the current sediment contamination in adjacent Rias. Variations in the accumulation rates suggest
different factors controlling the sedimentation processes including sediment sources and geomorphology.
Authors:A. Araújo, E. Fernandes, E. França, and M. Bacchi
Environmental quality assessment studies have been conducted with tree species largely distributed in the Atlantic Forest.
Leaf and soil samples were collected in the conservation unit Parque Estadual da Serra do Mar (PESM) nearby the industrial
complex of Cubatão, São Paulo State, Brazil, and analyzed for chemical elements by instrumental neutron activation analysis.
Results were compared to background values obtained in the Parque Estadual Carlos Botelho (PECB). The higher As, Fe, Hg and
Zn mass fractions in the tree leaves of PESM indicated anthropogenic influence on this conservation unit.
Authors:L. Cides, A. Araújo, M. Santos-Filho, and J. Matos
the present work, the thermal decomposition of glimepiride (sulfonylurea hypoglycemic
agent) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative
thermogravimetry (TG/DTG). Isothermal and non-isothermal methods were employed
to determine kinetic data of decomposition process. The physical chemical
properties and compatibilities of several commonly used pharmaceutical excipients
(glycolate starch, microcrystalline cellulose, stearate, lactose and Plasdone)
with glimepiride were evaluated using thermoanalytical methods. The 1:1 physical
mixtures of these excipients with glimepiride showed physical interaction
of the drug with Mg stearate, lactose and Plasdone. On the other hand,
IR results did not evidence any chemical modifications. From isothermal experiments,
activation energy (Ea)
can be obtained from slope of lntvs. 1/T at a constant
conversion level. The average value of this energy was 123 kJ mol–1.
For non-isothermal method Ea
can be obtained from plot of logarithms of heating rates, as a function of
inverse of temperature, resulting a value of 157 and 150 kJ mol–1,
respectively, in air and N2 atmosphere, from the first
stage of thermal decomposition.