Authors:A. M. Garrido Pedrosa, M. J. B. Souza, D. M. A. Melo, and A. S. Araujo
The thermo-programmed reduction study of Pt/WOx–ZrO2 materials prepared with different tungsten loading were performed by thermogravimetry. The samples were synthesized by impregnation method and calcined at 600, 700 and 800°C. The characterizations of both un-calcined and calcined materials were carried out using different techniques: thermal analysis (TG and DTA), X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA analysis of un-calcined were used to determination of calcination temperatures of the samples. XRD diffractograms were useful to help us in the determination of phase presents. TPR profiles showed between three and four events at different temperatures attributed to platinum reduction and the different stages of tungsten specie reduction.
Authors:A. Garrido Pedrosa, M. Souza, S. Lima, Dulce Melo, A. Souza, and A. Araújo
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
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:D. Melo, G. Vicentini, L. Zinner, K. Zinner, H. de Souza, M. Batista, A. Garrido Pedrosa, and R. Bezerra
Complexes of neodymium and europium with amides and aminoxides were synthesized and characterized by complexometric analyses
with EDTA, CHN microanalytical procedures, IR absorption spectra, absorption spectra of neodymium complexes, emission spectrum
of europium compounds at 77 K, thermogravimetric analyses in N2 and differential scanning calorimetry (DSC) in N2. Infrared
spectroscopy results revealed that the nitrate molecules are bound to the central ions as bidentate. Thermogravimetric plots
indicated that the decomposition of the complexes occurs in the range 363-1163 K and resulted in the formation of Ln2O3 residues.
Authors:A. Garrido Pedrosa, M. Câmara, F. Borges, H. de Souza, H. Scatena Jr, D. Melo, and L. Zinner
Complexes of rare earth trifluoroacetates (TFA) with 4-methylmorpholine-N-oxide (MMNO) of composition Ln(TFA)33MMNO (Ln=Eu, Dy, Ho, Er, Yb and Y) were synthesized and characterized by elemental analysis data, complexometric titration with EDTA,
IR absorption spectra, thermogravimetric analyses and differential scanning calorimetry (DSC) in N2 atmosphere. Infrared spectroscopy data revealed that the MMNO molecules are bound to the central ion through the oxygen of
NO groups. These data suggest that the trifluoracetate groups are also coordinated. Thermogravimetric curves indicate that
the decomposition of MMNO begins at approximately 350 K and results in Ln2O3 residue at around 1170 K. A theoretical kinetic study was carried out using a QBASIC program with the TG input data for the