Publicação
Phosphoric acid adsorbed on silica-ceria matrix obtained by sol-gel method: studies of local structure, texture and acid property
| Resumo: | SiO2/CeO2 mixed oxide (designated as SC) with variable ceria contents, SC1 = 5.6, SC2 = 8.0 and SC3 = 13.0 wt%, prepared by the sol-gel processing method, were obtained as amorphous solids possessing specific surface areas of SC1 = 463, SC2 = 474 and SC3 = 460 m²g-1. Phosphate ions were immobilized onto the surface of these solids through Ce-O-P bonding by immersing SC into a phosphoric acid solution. Solids with the following P contents were obtained (in atom %): SCP1 = 0.60, SCP2 = 0.71 and SCP3 = 1.63. The binding energy peak P 2p3/2 at ca. 134.0 eV, observed by XPS, and the 31P MAS NMR single peak, observed at ca. -10 ppm, revealed that H2PO4- is the species present on the surface of the matrices. Using pyridine as a molecular probe, only Brønsted acid sites could be detected. The amount of these acid sites, determined by ammonia gas adsorption on the surface, reached the following values for each phosphate-treated solid: SCP1 = 0.37, SCP2 = 0.43 and SCP3 = 0.51 mmol g-1. |
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| Autores principais: | Pissetti,Fábio L. |
| Outros Autores: | Francisco,Maria Suzana P.; Landers,Richard; Gushikem,Yoshitaka |
| Assunto: | silica-ceria silica-ceria-phosphate sol-gel method acid sites |
| Ano: | 2007 |
| País: | Brasil |
| Tipo de documento: | artigo |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | IBICT |
| Idioma: | inglês |
| Origem: | Oasisbr |
| Resumo: | SiO2/CeO2 mixed oxide (designated as SC) with variable ceria contents, SC1 = 5.6, SC2 = 8.0 and SC3 = 13.0 wt%, prepared by the sol-gel processing method, were obtained as amorphous solids possessing specific surface areas of SC1 = 463, SC2 = 474 and SC3 = 460 m²g-1. Phosphate ions were immobilized onto the surface of these solids through Ce-O-P bonding by immersing SC into a phosphoric acid solution. Solids with the following P contents were obtained (in atom %): SCP1 = 0.60, SCP2 = 0.71 and SCP3 = 1.63. The binding energy peak P 2p3/2 at ca. 134.0 eV, observed by XPS, and the 31P MAS NMR single peak, observed at ca. -10 ppm, revealed that H2PO4- is the species present on the surface of the matrices. Using pyridine as a molecular probe, only Brønsted acid sites could be detected. The amount of these acid sites, determined by ammonia gas adsorption on the surface, reached the following values for each phosphate-treated solid: SCP1 = 0.37, SCP2 = 0.43 and SCP3 = 0.51 mmol g-1. |
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