Aluminosilicate Solutions Research Articles

27Al NMR studies of aluminosilicate solutions. Influences of the second coordination sphere on the shielding of aluminium

Aluminosilicate solutions have been studied by 27Al NMR to investigate effects of the second coordination sphere on AI shielding. The spectra show four distinct peaks. 27A1 chemical shifts are compared with 29Si data. An analogous classification of the 27Al chemical shifts in terms of A1O 4 units of different environments and different degrees of condensation is proposed Observed resonances are correlated to aliminiumoxygen tetrahedra with different numbers of Si-O-Al bonds.

Hydrothermal chemistry of silicates. Part 21. Zeolites from reaction of lithium and caesium ions with tetramethylammonium aluminosilicate solutions

Gels formed by adding solutions of lithium and caesium chlorides to tetramethylammonium ‘aluminosilicate’ solutions have yielded a variety of crystalline products on heating. Among these, zeolites of rather narrow pore structure include variants of cancrinite, edingtonite, gismondine, sodalite, and the synthetic species Li-A(BW). More open zeolites obtained are variants of offretite, zeolites A(silica-rich), ZK5, and ZSM2. The non-zeolites pollucite, Cs-F, and lithium metasilicate have also been obtained. The composition, preheating, and ageing times of the synthesis mixtures have been adjusted in order to establish conditions for the crystallisation of pure species, e.g. ZK5 and ZSM2. The cation combination used is new in zeolite synthesis, and in this context the growth of offretite, N-A, and ZK5 is of particular interest. Zeolite ZSM2 has a remarkably open pore structure, and its sorption capacity equals that of faujasite. Its synthesis by the present method is also much faster than by that orignally used.