Synthesis and characterization of a new microporous cesium silicotitanate (SNL-B) molecular sieve

Ongoing hydrothermal Cs-Ti-Si-O-H2O phase investigations has produced sever al new ternary phases including a novel microporous Cs-silicotitanate molec ular sieve, SNL-B with the approximate formula of CS3TiSi3O9.5. 3H(2)O. SNL -B is only the second molecular sieve, Cs-silicotitanate phase reported to have been synthesized by hydrothermal methods. Crystallites are very small (0.1 x 2 mum(2)) with a blade-like morphology. SNL-B is confirmed to be a t hree-dimensional molecular sieve by a variety of characterization technique s (N-2 adsorption, ion exchange, water adsorption/desorption, solid state c ross polarization-magic angle spinning nuclear magnetic resonance). SNL-B i s able to desorb and adsorb water from its pores while retaining its crysta l structure and exchanges Cs cations readily. Additional techniques were us ed to describe fundamental properties (powder X-ray diffraction, FTIR,Si-29 and Cs-133 MAS NMR, DTA, SEM/EDS, ion selectivity, and radiation stability ). The phase relationships of metastable SNL-B to other hydrothermally synt hesized Cs-Ti-Si-O-H2O phases are discussed, particularly its relationship to a Cs-silicotitanate analogue of pharmacosiderite, and a novel condensed phase, a polymorph of Cs2TiSi6O15 (SNL-A). (C) 2000 Elsevier Science B.V. A ll rights reserved.