title: Silicon-29 NMR Studies of Tetraalkylammonium Silicate Solutions. 2. Polymerization Kinetics.
abstract: The kinetics of formation of the silicate cubic octamer, Q(3)(8), in aqueous tetramethylammonium (TMA) silicate solutions was investigated by (29)Si NMR. The rate equation for solutions at pH 13.2-13.6 is d[Q(3)(8)]/dt = k(f) [H(+)](1.6)(+/-)(0.1)[TMA(+)](0.36)(+/-)(0.08)[Si](0.8)(+/-)(0.3) where k(f) = (2.2 +/- 0.8) x 10(16) mol(-)(1.8) kg(1.8) s(-)(1) at 296 K. The findings prove unequivocally that alkylammonium cations participate directly in the formation and subsequent stabilization of cagelike polysilicate anions. This implies a radically different mechanistic role than "templating" for alkylammonium cations in the synthesis of molecular sieves.
authors.affiliation: Department of Chemistry, Lakehead University, Thunder Bay, Ontario, P7B 5E1, Canada, and School of Chemical Sciences, University of Illinois at Urbana-Champaign, 505 South Mathews Avenue, Urbana, Illinois 61801.
authors.forename: Stephen D.
authors.initials: SD
authors.lastname: Kinrade
authors.forename: Christopher T. G.
authors.initials: CT
authors.lastname: Knight
authors.forename: David L.
authors.initials: DL
authors.lastname: Pole
authors.forename: Raymond T.
authors.initials: RT
authors.lastname: Syvitski