Da. Donatti et Dr. Vollet, A CALORIMETRIC STUDY OF THE ULTRASOUND-STIMULATED HYDROLYSIS OF SOLVENTLESS TEOS-WATER MIXTURES, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 4(2), 1995, pp. 99-105
The kinetics of ultrasound-stimulated and HCl-catalyzed hydrolysis of
solventless TEOS-water mixtures was studied as a function of temperatu
re ranging from 10 degrees C up to 65 degrees C by means of flux calor
imetry measurements. A specially designed device was utilized for this
purpose. The exothermic peak arising few minutes after sonication beg
an has been attributed mainly to the hydrolysis reaction. The overall
hydrolysis process, which was measured through the irradiation time up
to the hydrolysis peak, was found to be thermally activated, with an
apparent activation energy Delta E = 36.4 kJ/mol. The alcohol produced
at the early hydrolysis due to sonication seems to further enhance th
e reaction, via a parallel autocatalytic path, which is controlled by
a faster pseudo second order rate constant (k'). Our modeling yielded
k' = 6.3 x 10(-2) M(-1) min(-1) at 20 degrees C, which is in a reasona
ble agreement with the literature, and an activation energy Delta E =
40.4 kJ/mol for the specific process of hydrolysis in presence of alco
hol.