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.