ZSM-5/SBA-15 microporous/mesoporous composites prepared by a microwave-assisted zeolitisation of Al-SBA-15 mesoporous solids

ZSM-5/SBA-15 composites with high textural properties were synthesised by a microwave-assisted zeolitisation of Al-SBA-15 in the presence of tetrapropylammonium bromide. The effect of the hydrothermal treatment temperature and of ammonium fluoride, often used as a catalyst, was studied. Resulting materials were characterised by XRD, SEM, N2 sorption, HR-TEM, hyperpolarised Xe NMR, pyridine sorption as well as by their stability toward boiling water. It was shown that the hydrothermal synthesis has to be carried out at 140 °C in order to better preserve the structure of the mesoporous precursor. Composite materials could be obtained only from a fluoride-free synthesis at short crystallisation times, t < 5 h. Appearance of 2–5 nm nanoparticles in some of the corresponding samples, has been related to the increase in the total acidity. Inclusion of zeolitic material in the remaining Al-SBA-15 structure was demonstrated by hyperpolarised xenon NMR studies.

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► ZSM-5/SBA-15 solids were prepared by microwave-assisted zeolitisation.
► 2–4 nm spherical crystalline nanoparticles could be detected by HR-TEM measurements.
► Inclusion of zeolite embryos in the mesopore network was shown by HP Xe NMR.
► Total number of acid sites is approximately the average of pure ZSM-5 and Al-SBA-15.