A KINETIC-MODEL FOR THE ULTRASOUND CATALYZED-HYDROLYSIS OF SOLVENTLESS TEOS-WATER MIXTURES AND THE ROLE OF THE INITIAL ADDITIONS OF ETHANOL

The acid and ultrasound catalyzed hydrolysis of solventless TEOS-water mixtures are studied, as a function of the initial additions of ethan ol to the mixtures, by means of flux calorimetry measurements. A devic e was specially designed for this purpose. Under acid conditions, our proposed method has been able to resolve hydrolysis from other condens ation reactions, by detecting the exothermal hydrolysis reaction heat. The process has been explained by a dissolution and reaction mechanis m. Ultrasound forces the dissolution process to start the reaction. Th e alcohol produced in the reaction helps the dissolution process to fu rther enhance the hydrolysis. Initial amounts of pure ethanol added to the mixtures shorten the start time of the reaction, due to an additi onal effect of dissolution, and diminish the reaction rate, as a resul t of the solvent dilution effect. Our dissolution and reaction mechani sm modeling describes the main points arising from the experimental da ta and yields k(H) = 0.24 M(-1) min(-1) for the second-order hydrolysi s rate constant at 39 degrees C.