REACTION BETWEEN ALUMINUM NITRATE NONAHYDRATE AND TETRAETHOXYSILANE IN ETHANOL

The reaction between aluminum nitrate nonahydrate and tetraethoxysilan e in ethanol was followed by NMR of the Si-29 nucleus. The results sho wed the initial hydrolysis and condensation to be fast to an extent th at no monomeric species of the silicon compounds were found after mixi ng for three minutes. In addition, the results showed the condensation reaction to be fast compared to the hydrolysis. This fact was demonst rated by the extremely high ratio of ethoxy groups to OH groups in the different specia (SiO)y Si(OH)x (OC2H5)4-x-yThe reaction proceeded wi thout added acid and gave gels of silica with colloidally dispersed al uminum nitrate. The protons to catalyze the reaction emanated from the hydrated aluminum salt; titration by sodium hydroxide revealed the hy drate to be a strong acid in ethanol with a titration point showing th ree moles of base per mole of aluminium salt.