Síntese pelo método da coprecipitação e caracterização estrutural do tungstato de cálcio com estrutura tipo scheelita

Vieira, Ewerton Gomes; Sousa, P.; Matos, José Milton Elias de; Santos, M. R. M. C.

doi:10.1590/s0366-69132013000300011

Cited by 14 publications

(7 citation statements)

References 45 publications

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“…UV-Vis spectroscopy measurements were performed in the diffuse reflectance mode and the optical band gap energy (Eg) was calculated by the method proposed by Kubelka-Munk for any wavelength 11,36 . The Figure 4 shows the Eg obtained and Table 2 shows the Eg values obtained in this work and values found in the literature 11,[37][38][39][40] . Differences of Eg value may be related to particle morphology, type of synthesis, time and temperature of the process.…”

Section: Uv-visible Absorption Measurementsmentioning

confidence: 68%

Effect of Different Synthesis Methods on the Textural Properties of Calcium Tungstate (CaWO4) and Its Catalytic Properties in the Toluene Oxidation

et al. 2018

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Calcium tungstate (CaWO 4) crystals were prepared by microwave-assisted hydrothermal (MAH) and polymeric precursor methods (PPM). These crystals were structurally characterized by X-ray diffraction (XRD), N 2 adsorption, X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. The morphology and size of these crystals were observed by field emission scanning electron microscopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-Vis) absorption and photoluminescence (PL) measurements. Moreover, these materials were employed as catalysts towards gas phase toluene oxidation reaction. XRD indicates the purity of materials for both preparation methods and MAH process produced crystalline powders synthesized at lower temperatures and shorter processing time compared to the ones prepared by PPM. FE-SEM images showed particles with rounded morphology and particles in clusters dumbbellslike shaped. PL spectra exhibit a broad band covering the visible electromagnetic spectrum in the range of 360 to 750 nm. XANES and EXAFS results show that preparation method does not introduce high disorders into the structure, however the H 2-TPR results indicated that the catalyst reducibility is affected by the preparation method of the samples.

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Section: Uv-visible Absorption Measurementsmentioning

confidence: 68%

Effect of Different Synthesis Methods on the Textural Properties of Calcium Tungstate (CaWO4) and Its Catalytic Properties in the Toluene Oxidation

et al. 2018

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“…O catalisador CoWO4 apresenta uma estrutura do tipo wolframita e sistema cristalino monoclínico, em que o átomo de tungstênio apresenta geometria octaédrica. Sua fase foi confirmada pela presença dos picos em 18, 9°, 23,8°, 24°,6°, 30,6°, 36,3°, 38,5°, 53,9°, 54,0° (código 15-0867) (VIEIRA et al, 2013). O catalisador Ca0,5Co0,5WO4 apresentou picos com menor intensidade referentes aos tungstatos: CaWO4 e CoWO4.…”

Section: Resultsunclassified

Estudo da decomposição de óxido nitroso sobre tungstatos de cálcio e/ou cobalto

Santos

Gonçalves

Batista

2019

BJD

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“…O catalisador CoWO 4 apresenta uma estrutura do tipo wolframita e sistema cristalino monoclínico, em que o átomo de tungstênio apresenta geometria octaédrica. Sua fase foi confirmada pela presença dos picos em 18, 9°, 23,8°, 24°,6°, 30,6°, 36,3°, 38,5°, 53,9°, 54,0° (código 15-0867) (VIEIRA et al, 2013) (GALLUCCI et al, 2002).…”

Section: Resultsunclassified

Estudo Da Decomposição De Óxido Nitroso Sobre Tungstatos De Cálcio E/Ou Cobalto

Santos

Gonçalves

Batista

2018

Blucher Chemical Engineering Proceedings

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RESUMO -A decomposição de N 2 O é uma rota alternativa para reduzir a emissão desse gás em processos industriais. Essa rota catalítica se destaca pela simplicidade e baixo custo. Catalisadores CaWO 4 , CoWO 4 e Ca 0,5 Co 0,5 WO 4 foram preparados pelo método de co-precipitação, caracterizados por DRX e MEV e avaliados na decomposição de N 2 O. Os resultados mostraram a formação de estruturas com morfologia irregular do tipo wolframita para o CoWO 4 e scheelita para o CaWO 4 . O catalisador Ca 0,5 Co 0,5 WO 4 apresentou os picos de menor intensidade referentes aos tungstatos precursores. Os tungstatos foram ativos para a decomposição de N 2 O, seguindo a ordem de atividade CoWO 4 > CaWO 4 > Ca 0,5 Co 0,5 WO 4 , mostrando potencial aplicação na catálise heterogênea.

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Síntese pelo método da coprecipitação e caracterização estrutural do tungstato de cálcio com estrutura tipo scheelita

Abstract: CaWO 4 nanocrystals were synthesized by the coprecipitation method of with different solvent ratio (water/ethylene glycol)

Cited by 14 publications

References 45 publications

Effect of Different Synthesis Methods on the Textural Properties of Calcium Tungstate (CaWO4) and Its Catalytic Properties in the Toluene Oxidation

Effect of Different Synthesis Methods on the Textural Properties of Calcium Tungstate (CaWO4) and Its Catalytic Properties in the Toluene Oxidation

Estudo da decomposição de óxido nitroso sobre tungstatos de cálcio e/ou cobalto

Estudo Da Decomposição De Óxido Nitroso Sobre Tungstatos De Cálcio E/Ou Cobalto

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