Journal
JOURNAL OF SOLID STATE CHEMISTRY
Volume 312, Issue -, Pages -Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jssc.2022.123296
Keywords
Zr-SBA-15; Mesoporous; Direct synthesis; pH adjustment; Heteroatomic incorporation; High charge
Ask authors/readers for more resources
By incorporating heteroatomic species, acidity in SBA-15 can be enhanced, providing a new strategy for preparing efficient catalysts. The study showed that Zr-SBA-15 materials prepared by the pH-adjusting approach exhibit better structural, textural, and acidic properties compared to those prepared by direct synthesis.
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 degrees 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 Bronsted 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.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available