Hydrolysis of methylphenyldiethoxysilane with rare earth superacid catalysts SO _4 ~2/TiO _2/Ln ~(3+)

摘要

An environmentally benign hydrolysis of methylphenyldiethoxysilane (MePhSi(OEt) 2) catalyzed by a rare earth superacid catalyst SO 2- 4/TiO 2/Ln 3+ has been investigated. The hydrolysis rates decrease in the order SO 2- 4/TiO 2/Nd 3+ > SO 2- 4/TiO 2/Y 3+ > SO 2-4/TiO 2/Sm 3+ > SO 2-4TiO 2. The hydrolysis of MePhSi(OEt) 2 is a first-order reaction with respect to the concentration of MePhSi(OEt) 2, and the hydrolysis rate constant increases with increasing temperature. The activation energy E a and the pre-exponential factor for this hydrolysis catalyzed by SO 2- 4/TiO 2/Nd 3+ have been determined as 322.50 kJ mol -1 and 7.12 × 10 41 s -1, respectively. The products of the hydrolysis are oligomers of polymethylphenylsiloxane. The mechanism of MePhSi(OEt) 2 hydrolysis is also discussed.