Nanostructured KIT-6 materials functionalized with sulfonic groups for catalytic purposes

In the present study, a series of ordered nanostructured KIT-6 silica, functionalized with different numbers of sulfonic groups (–SO3H) introduced by grafting or co-condensation, were synthesized. The obtained samples were subjected to thorough physicochemical characterization using X-ray diffraction, transmission electron microscopy, low temperature nitrogen sorption, infrared spectroscopy and elemental analysis. It has been observed that the amount of the used functional group precursor clearly affects the structural and textural parameters of the studied materials synthesized by co-condensation. On the other hand, the samples modified by grafting, irrespective of the number of the introduced –SO3H groups, exhibit a stable mesoporous structure with Ia3d symmetry, characteristic of KIT-6 materials. The developed synthesis procedures yielded potential solid acid catalysts, which were used in the test catalytic reactions: Friedel-Crafts alkylation, fatty acid esterification and Pechmann condensation. Both the developed synthesis algorithm and the catalytic reaction procedures comprised elements of "green chemistry", as the transformation of the functional groups precursor (–SH to –SO3H) took place in the presence of H2O2, an oxidant considered to be environmentally friendly, while the catalytic reactions were carried out without solvents and under microwave-assisted conditions, which allowed a significant shortening of the reaction time.

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