Banca de DEFESA: RAFAEL HERNANDEZ DAMASCENA DOS PASSOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : RAFAEL HERNANDEZ DAMASCENA DOS PASSOS
DATA : 06/12/2018
HORA: 10:00
LOCAL: auditorio da CeT
TÍTULO:

Catalytic and electrical properties of strontium and cerium tungstate:
Conversion of methane

PALAVRAS-CHAVES:

Nanostructured ceramics; scheelite; EDTA-Citrate; TGA-DTA; XRD; TEM;
Rietveld.

PÁGINAS: 104
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Química
RESUMO:

Nanoparticles of cerium and strontium tungstate have been prepared from the
method of synthesis of the ceramic powders involved the complexation combining EDTA-citrate
in order to determine the catalytic activity and the electrical properties of the obtained materials.
The syntheses produced strontium (SrWO4), cerium (Ce2W3O12) tungstates and a ternary
tungstate composed of Sr and Ce identified with structure Sr0.5Ce0.35□0.15WO4. In the interest of
characterize them, TG-DTG, XRD and MET analyzes were performed. TG-DTG analyzes determined
that material with crystalline structure could be obtained from 600°C. The diffractograms
indicated tetragonal crystalline structure with spatial group I41/a (N° 88) for SrWO4 and
monoclinic structure belonging to space group C2/c (Nº 15) for Ce2(WO4)3. The TEM images
allowed us to determine the mean crystallite size that were shown to be compatible with the
results calculated from the Williamson-Hall equation. Refined XRD analysis using the Rietveld
method, high-resolution transmission electron microscopy (HRTEM) images and electronic
diffraction were applied to study the ternary tungstate and to define its composition and crystalline
structure as tetragonal belonging to the space group I4̅ (N° 82). Analyzes were conducted
to determine the catalytic activity in partial oxidation of CH4 considering a 3³ experimental
design where the parameters analyzed were reaction temperature, CH4 concentration and catalyst
type at three different levels. It was observed that the most relevant parameters for the CH4
oxidation reaction were the type of catalyst and the reaction temperature, respectively. The
concentration was not relevant to the result and the most efficient catalyst to convert CH4 into
synthesis gas (H2 + CO) was, in descending order, SrWO4, Sr0.5Ce0.35□0.15WO4 and Ce2(WO4)3.
Moreover, the electrical properties analysis determined the activation energies of the samples,
the result was 1.42eV, 1.16eV and 0.99eV for SrWO4, Sr0.5Ce0.35□0.15WO4 and Ce2(WO4)3, respectively

MEMBROS DA BANCA:
Presidente - 349801 - CARLSON PEREIRA DE SOUZA
Externo à Instituição - CESAR AUGUSTO MORAES DE ABREU - UFPE
Externo à Instituição - CHRISTINE LEROUX - UTV
Externo à Instituição - ELSON LONGO DA SILVA - UNESP
Externo à Instituição - JEAN HENRY FERRASSE
Externo à Instituição - MADJID ARAB - UTV
Externo à Instituição - SIBELE BERENICE CASTELLA PERGHER
Externo à Instituição - VANESSA COULET