Synthesis and characterization of mesoporous materials with acid properties

VERGARA LOURDES; SÁNCHEZ, BÁRBARA; MENDOW, GUSTAVO; QUERINI, CARLOS

Santa Fe

Workshop; French Argentinean Workshop on Heterogeneous Catalysis; 2023

INCAPE-IC2MP

The synthesized mesoporous materials were KIT-6, FDU-12, Silica Nanotubes (NTS), SBA-15, SBA-15 large pore, SBA-16, mesoporous SnO2 and MCM-48 silicas. In all cases, Tetraethylorthosilicate (TEOS) was used as silicon source, and mecaptopropyl-trimethoxysilane (MPTMS) as a precursor of the sulfonic groups. In some materials the Pluronic P-123 copolymer was used as template, and in others Pluronic F-127 and CTAB. The synthesis conditions (temperature, hydrothermal treatment) were different for each support, following procedures published in the literature.For the incorporation of propylsulfonic groups with the objective of generating acidity, three alternatives were explored:(i) Co-condensation 1 (C1): Functionalization with mercapto groups (-SH) during the synthesis and subsequent oxidation to sulfonic groups (-SO3H) [1].(ii) Co-condensation 2 (C2): Functionalization with -SH groups and oxidation to -SO3H in the same step [2].(iii) Grafting (G): Functionalization with -SH groups post-synthesis followed by oxidation [3].With the three methods, catalysts with different contents of functional groups were prepared: 10 and 15%, expressed as %mol/mol S/Si.Textural properties were determined by N2 adsorption-desorption isotherms. The specific surface area was estimated by BET method and the pore size distribution was calculated using the Broekhoff-de Boer (BdB) method for adsorption branches. The S/Si ratios on the silicas were measured by energy dispersive X-ray fluorescence (XRF) (EDX). Acidity measurements were made by potentiometric titration with butylamine using acetonitrile as solvent. The efficiency of the mercapto groups oxidation treatment was evaluated with thermogravimetric analysis (TGA) and qualitatively, by N2 stripping at programmed temperature.