Simultaneous removal of copolymer template from SBA-15 in the crystallization process

Abstract

The triblock copolymer templates were successfully removed from as-synthesized mesoporous molecular sieve SBA-15 by a new treatment process with H 2O 2 as oxidizing agent, and the process couples the crystallization process into one step to make the synthesis process compact. The effect of operation conditions on removal efficiency was investigated, including treating time and temperature, H 2O 2 concentration, and the quantity ratio of H 2O 2 to organic templates. The prepared mesoporous SBA-15 materials by the new process, characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and hydrothermal stability experiments, exhibited higher surface areas, larger micropore volumes, more uniform particle sizes and higher density of silanol groups on the pore wall than those obtained by conventional methods. Moreover, the removal of templates in the crystallization process facilitates a further condensation and mild shrinkage of the silica framework, and rearrangement of the materials, which prevents the hydrothermally treated SBA-15 materials from shrinking significantly during subsequent calcination and makes them show higher hydrothermal stabilities.