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

Author(s)

Lorena Dariane da Silva Alencar ^[1] ; Naiara Arantes Lima ^[1] ; Alexandre Mesquita ^[2] ; Luiz Fernando Dias Probst ^[3] ; Daniel Carreira Batalha ^[4] ; Marcelo Gonçalves Rosmaninho ^[6] ; Humberto Vieira Fajardo ^[4] ; Rosana Balzer ^[6] ; Maria Inês Basso Bernardi ^[9]

Affiliation

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13563120 Sao Carlos, SP - Brazil

^[2] Univ Estadual Paulista, UNESP, Dept Fis, Inst Geociencias & Ciencias Exatas, BR-13506900 Rio Claro, SP - Brazil

^[3] Univ Fed Santa Catarina, Dept Quim, BR-88040900 Florianopolis, SC - Brazil

^[4] Univ Fed Ouro Preto, Inst Ciencias Exatas & Biol, Dept Quim, BR-35400000 Ouro Preto, MG - Brazil

^[5] Universidade Federal de Ouro Preto. Instituto de Ciências Exatas e Biológicas. Departamento de Química - Brasil

^[6] Univ Fed Parana UFPR, Dept Engn & Exatas, BR-85950000 Palotina, PR - Brazil

^[7] Universidade de São Paulo. Instituto de Física de São Carlos - Brasil

• Document type: Journal article
• Source: MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS; v. 21, n. 3 2018-04-16.

Abstract

Calcium tungstate (CaWO4) crystals were prepared by microwave-assisted hydrothermal (MAH) and polymeric precursor methods (PPM). These crystals were structurally characterized by X-ray diffraction (XRD), N2 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 dumbbells-like 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 H2-TPR results indicated that the catalyst reducibility is affected by the preparation method of the samples. (AU)

• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 13/07909-4 - Preparation and characterization of magnetic oxides films nanostructured
• Grantee: Maria Inês Basso Bernardi
• Support Opportunities: Regular Research Grants