Surface functionalization of mesoporous silica nanoparticles with brønsted acids as a catalyst for esterificatsion reaction

This work presents the preparation of mesoporous silica nanoparticles (MSNs) using Stöber process. Then, the MSNs surface was modified with propyl thiol, followed by conversion of thiol to sulfonic acid using H2O2, acetic acid/H2O2, HNO3/H2O2, and H2SO4/H2O2. Surface modified MSNs were characterized by a variety of techniques: the Brunauer, Emmett and Teller (BET) technique, thermogravimetric analysis (TGA), scanning and transmission electron microscopies (SEM and TEM), dynamic light scattering (DLS) and Fourier-transform infrared spectroscopy (FTIR). The size of unmodified and modified MSNs ranged between 200 and 320 nm, with pore size of ca. 5.0 nm and surface area ca. 900 m2/g. The surface zeta potential was of the fabricated nanomaterials was estimated to be between −35 and −43 mV. When the surface modified MSNs were subjected to esterification reaction between heptanol and acetic acid, the conversion to ester reached 75% in the presence of MSNs-Pr-SO3H (via H2SO4/H2O2), comparing to MSNs-Pr-SO3H (via H2O2) or MSNs-Pr-SO3H (via Ac/H2O2). The conversion increased 75% to 93% for MSNs-Pr-SO3H (via H2SO4/H2O2) when the temperature increased from 90 °C to 110 °C, respectively.