Kinetic Study of Alkoxysilane Hydrolysis under Acidic Conditions by Fourier Transform Near Infrared Spectroscopy Combined with Partial Least-Squares Model

Fourier transform near-infrared (FT-NIR) spectroscopy combined with a partial least-squares (PLS) model was successfully employed to study the hydrolysis kinetics of dimethyldiethoxysilane, methyltriethoxysilane, and tetraethoxysilane in an acid-catalyzed EtOH system. The high scanning speed and high sensitivity of FT-NIR spectroscopy enabled the new method to catch the rapid changes of the H₂O and EtOH concentrations without delay, allowing the kinetic behaviors of the hydrolysis reactions of the specified alkoxysilanes to be investigated. The hydrolysis processes were found to follow second-order reactions. The hydrolysis rate constants, activation energies, and Arrhenius frequency factors were obtained. The FT-NIR PLS results were in good agreement with those determined by Fourier transform midinfrared spectroscopy. However, the FT-NIR PLS method was found to be more accurate, because of the powerful data processing ability of PLS. All of the results suggest that the FT-NIR PLS model is a valuable tool for performing kinetic research.