KIT-5 Structural and Textural Changes in Response to Different Methods of Functionalization with Sulfonic Groups

In this project, KIT-5 materials were effectively functionalized with sulfonic groups introduced by grafting or the co-condensation method and tested as heterogeneous solid acid catalyst. A co-condensation procedure leading to the stable, -SO3H functionalized KIT-5 materials was successfully established. Moreover, the influence of both synthesis methods on the structural and textural parameters, as well as surface chemistry, morphology, and catalytic activity of -SO3H/KIT-5 materials was thoroughly investigated. The syntheses with 3-mepkaptopropyltrimethoxysilane (MPTMS) acting as a modifying agent resulted in samples in which functional groups were introduced into the structure and/or onto the mesoporous silica surface. The oxidation stage of -SH to -SO3H groups was carried out under mild conditions, using a green oxidant (H2O2). The application of different functionalization techniques and the introduction of different amounts of modifying agent allowed for an evaluation of the influence of these parameters on the ordering of the mesoporous structure of KIT-5 materials. The applied methods of assessment of the physicochemical parameters (XRD, low-temperature N-2 sorption, TEM) showed that, especially when the co-condensation method was applied, as the number of functional groups increased, the ordering of structure characteristic of KIT-5 decreased. On the other hand, the samples modified by grafting had a stable structure, regardless of the amount of introduced MPTMS. Test reactions carried out on the basis of Friedel-Crafts alkylation process showed that the synthesized materials can be considered promising acid catalysts in heterogeneous catalysis reactions.

Automated summary

In this study, KIT-5 materials were effectively functionalized with sulfonic groups using grafting or the co-condensation method and tested as solid acid catalysts. The co-condensation method successfully produced stable -SO3H functionalized KIT-5 materials. The influence of synthesis methods on various parameters and the catalytic activity of -SO3H/KIT-5 materials was thoroughly investigated. Different functionalization techniques and modifying agent amounts were evaluated for their impact on the ordering of the mesoporous structure of KIT-5 materials. The synthesized materials showed promise as acid catalysts in heterogeneous catalysis reactions, particularly in Friedel-Crafts alkylation processes.