MULTINUCLEAR MAGNETIC-RESONANCE CHARACTERIZATION OF VARIOUS ALUMINOSILICATE GELS IN THE PRESENCE OF TETRAALKYLAMMONIUM IONS

Four gels of initial compositions 8 TAABr:Al2O3:90 SiO2:1,000 H2O (gel I), 8 TAAOH:Al2O3:90 SiO2: 1,000 H2O (gel II), 2 TAAOH:Al2O3:200 H2O (gel III), and 8 TAABr:4.5 Na2O:Al2O3:90 SiO2: 1,000 H2O (gel IV) were prepared and dried at 363 K (TAA = tetramethyl, tetraethyl, tetrapropyl, and tetrabutylammonium). The dried gels were characterized by C-13, Al-27, and Si-29 n.m.r. and the calcined gels by Xe-129 n.m.r. of adsorbed xenon. The Al atoms are very well dispersed in a tetrahedral form of the get structure in gel II, rather well dispersed in gel IV, and partially dispersed in gel I. In gels I and IV, large and medium size cavities contained aggregated (crystalline) TAABr and less aggregated species. Only gel II is able to disperse the TAA ions in monomeric forms where they ate countercations to gel negative charges. The monomeric TAA species could play a direct role in zeolite synthesis.