High zirconium loads in Zr-SBA-15 mesoporous materials prepared by direct-synthesis and pH-adjusting approaches
SBA-15 is a material with interesting characteristics associated with the size, order, uniformity, and pores distribution. However, the absence of acidity in SBA-15 restricts its applications as a potential acid catalyst in the industry for the large-scale production of fuels and chemicals. Mesoporo...
| Autores: | , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/379250 |
| Acceso en línea: | https://hdl.handle.net/2117/379250 https://dx.doi.org/10.1016/j.jssc.2022.123296 |
| Access Level: | acceso abierto |
| Palabra clave: | Solid state chemistry Zr-SBA-15 Mesoporous Direct synthesis pH adjustment Heteroatomic incorporation High charge Química de l'estat sòlid Àrees temàtiques de la UPC::Enginyeria química |
| Sumario: | SBA-15 is a material with interesting characteristics associated with the size, order, uniformity, and pores distribution. However, the absence of acidity in SBA-15 restricts its applications as a potential acid catalyst in the industry for the large-scale production of fuels and chemicals. Mesoporous SBA-15 modified by the incorporation of heteroatomic species can be a good strategy to include acidity and prepare an efficient catalyst. In this work, we present a comparative study in the preparation of SBA-15 and Zr-SBA-15 mesoporous materials with high zirconium loads (Si/Zr ¿= ¿10, 5, and 2) using direct-synthesis and pH-adjusting approaches with a low crystallization temperature of 60 ¿°C. The materials were characterized using XRPD, HRTEM, ICP, SEM-EDS, XPS, DRS UV-VIS, FT-IR, NH3-TPD, in situ FT-IR with pyridine probe, and N2-physisorption. Characterization by ICP and SEM-EDS indicated that the Si/Zr molar ratio of Zr-materials prepared by the pH adjustment better matched the nominal values. N2-physisorption showed that the mesoporosity of the materials was preserved even at the high Zr load. XRPD and HRTEM pointed out that Zr-SBA-15 materials prepared by the pH adjustment showed a higher level of ordering in the porous network. Regardless of the synthesis approach, the presence of a higher Zr load caused a loss in the structural ordering. It must be highlighted that the high-resolution XPS spectra of Zr 3d suggested the formation of Si–O–Zr bonds giving some indication of Zr incorporation into the SBA-15 framework. The formation of Si–O–Zr linkage in the Zr-materials was also corroborated by DRS UV-VIS due to the presence of a blue shift in the absorption edge for both series of the Zr-SBA-15 materials. NH3-TPD and in-situ FT-IR spectroscopy with pyridine probe showed that the presence of Zr species introduces acidity in the SBA-15 and at higher Zr load the Brønsted acidity increased particularly for the Zr-materials prepared by pH adjustment. In conclusion, this study evidences that the pH-adjusting approach improves structural, textural, morphological, and acidic properties in SBA-15 and Zr-SBA-15 materials compared to the direct-synthesis approach. |
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