Improved hydrothermal stability and acidic properties of ordered mesoporous SBA-15 analogs assembled from nanosized ZSM-5 precursors

Ordered hexagonal mesoporous materials have been successfully synthesized in a two-step process from assembly of pre-formed nanoscale ZSM-5 precursors at elevated temperature by pH adjusting during synthesis. The resulting materials were characterized by small-angle X-ray scattering (SAXS), N2 adsorption and desorption (BET), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (NH3-TPD), FTIR spectroscopy of pyridine adsorption–desorption (pyr-FTIR), atomic absorption spectroscopy (AAS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). It was found out that a highly ordered mesoporous material with both improved hydrothermal stability and acidic properties can be optimally prepared at pH 3.5 and 200 °C. The ordered mesostructure of such material is well preserved even after steaming at 800 °C for 4 h, with little loss in BET specific surface of 10.7% only, while its acidic properties are significantly enhanced in terms of both acid strength and total acidity. These improved properties can be attributed to the synergistic advantages of the use of zeolite nanoseeds, high temperature synthesis and pH adjustment.

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► High-temperature synthesis of ordered mesoporous materials from ZSM-5 nanoseeds.
► Increased acidity and hydrothermal stability of SBA-15 analogs.
► Control of nanoseed properties by SAXS measurement.
► Effect of hydrothermal treatment pH on the final material properties.