The role of Nb in the formation of sulphonic species in SBA-15 and MCF functionalised with MPTMS

Mesoporous silica and niobiosilicate materials of SBA-15 and MCF types were prepared in the presence of MPTMS, i.e. (3-mercaptopropyl)trimethoxysilane and hydrogen peroxide. The samples obtained were characterised by different techniques (N2 adsorption/desorption, XRD, elemental and thermal analyses) and applied as catalysts in glycerol esterification with acetic acid. The role of niobium species on the formation of sulphonic species and stability of organosilane modifier was explored. The most important finding is that the addition of niobium to the synthesis gel improves the efficiency of –SH oxidation by hydrogen peroxide towards sulphonic species. This behaviour is not dependent on the type of structure of mesoporous materials (SBA-15 or MCF). However, the kind of mesoporous solid influences the efficiency of Nb incorporation and on the esterification process. MCF matrix improves the catalytic performance of the MPTMS modified catalyst.

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► For both modified SBA-15 and MCF samples niobium enhanced the oxidation of thiol species (MPTMS).
► Niobium had an impact on the drop of methoxy species oxidation (MPTMS).
► NbMCF modified samples were more active than NbSBA-15 in the esterification process.