The use of catalysts in numerous important processes is widespread throughout the chemical and petroleum-processing industries.
Thermal analytical techniques can be used to evaluate important properties and processes associated with solid catalysts.
This paper presents examples carried out in our laboratory of the general application of TG and DSC to the acidity, activity
and regeneration of solid catalysts.
Authors:A. de Araujo, V. Fernandes, and G. Fernandes
The acid properties of the Ca/NaY zeolite were investigated by means ofn-butylamine desorption and thermal decomposition, using both thermogravimetry (TG) and differential scanning calorimetry (DSC).
The total acidity of the zeolite was calculated from the TG data, while DSC was used with the Borchardt-Daniels kinetic model
to determine the relative acid strength of the catalyst, given in J per acid site. The enthalpies of these processes are proportional
to the acid site strength in each specific temperature range.
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:P. Álvarez-Iglesias, M. Araújo, A. Gouveia, and T. Drago
Two sediment cores (~30 m long) were retrieved at the mouth of the Minho Estuary to assess its palaeoenvironmental evolution
for the last millennia. Samples were characterized by Energy-Dispersive X-Ray Fluorescence Spectrometry and Instrumental Neutron
Activation Analysis, complemented by sedimentological analyses. Provenance of major and trace element contents (lithogenic
or biogenic, continental or marine) is assessed. The influence of grain size effect on total element concentration is discussed.
Most of the samples present a negative Eu anomaly. Sedimentological and geochemical parameters allow differentiating four
geological units––fluvial, marine, estuarine and sand barrier––which reflects the temporal evolution of the Minho Estuary.
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: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.