Micro-Raman monitoring of solvent-free TEOS hydrolysis

The ethanol-free hydrolysis of tetraethyl-orthosilicate (TEOS) at normalities N = 0.1 and N = 0.01 of HBr, HCl, HNO3 and H2SO4 has been studied, during the first stages of the process by in situ micro-Raman spectroscopy, following the intensities of TEOS and ethanol characteristic vibrational features. The time required for a complete vanishing of the 656 cm−1 Raman peak of TEOS increases with decreasing strength of the acid catalyst for N = 0.1, whereas, at lower acid concentrations, longer hydrolysis times are needed, irrespective of catalyst type.