Direct Synthesis and Characterization of Zr-SBA-15 Mesoporous Molecular Sieves

Abstract

This work reports the synthesis and characterization of Zr-SBA-15 mesoporous molecular sieves via direct synthesis, with Zr(NO₃)₄·3H₂O as the zirconium source. The surface features, crystalline structure and textural properties are characterized by X-ray diffraction, nitrogen adsorption-desorption isotherms, transmission electron microscopy, thermogravimetry-differential thermal analysis and electron diffraction spectroscopy. The XRD patterns and TEM micrographs of the calcined samples show the characteristic diffraction peaks of the tetragonal ZrO₂ and the ordered mesostructure in frameworks. The largest Zr/Si molar ratio during Zr-SBA-15 synthesis is 2.1. Similarly, the Brunauer-Emmett-Teller (BET) area also shows a decreasing tendency, which agrees with the XRD patterns. When the Zr/Si ratio was over 1.5, the characteristic peaks of the tetragonal ZrO₂ phase can be observed. However, when the Zr/Si ratio is 1.5 or less, the samples have a high surface area (i.e., greater than 398 m²/g), with pore diameters of approximately 7.40 nm, which are within the limits for mesoporous materials.