Hydrothermal chemistry of silicates. Part XV. Synthesis and nature of some salt-bearing aluminosilicates

Abstract

It was earlier shown to be possible to synthesise novel salt-bearing aluminosilicates termed P, Q, N, and O, and to obtain molecular sieve sorbents from one of these. These aluminosilicates have now been characterised by extending the conditions of synthesis and by crystallographic and chemical investigations. Syntheses, especially of P and Q, can be effected not only from gels but also from a range of crystalline aluminosilicates. The species containing BaCl₂ and BaBr₂(respectively species P and Q) are based upon the same aluminosilicate framework as the synthetic zeolite ZK-5 while those containing KCl and KBr (respectively species N and O) are based upon the framework of the synthetic zeolite K–F reported in 1956. P and Q differ from ZK-5 notably in the salt content and exchange ions. In addition the variants P′ and Q′ were synthesised, which represent aluminous modifications of the ZK-5 framework, as well as an iodide-bearing form of zeolite K–F. Both K–F and ZK-5 frameworks were greatly heat-stabilised by the intracrystalline salts.

The removal of barium halides, by extraction with distilled water and various electrolyte solutions, has been investigated for P, Q, P′, and Q′. Solutions of NaNO₃ or LiNO₃ are much more effective than distilled water. The influence of electrolyte type and concentration, of temperature, of the proportion of crystals to electrolyte solution of fixed concentration, and of time, upon the removal of barium halides have been particularly studied, to optimise the preparation of molecular sieve zeolites.