Crystallization kinetics of Na7.4(AlSiO4)6(CO3)0.7·4H2O, an intermediate phase between cancrinite and sodalite, grown under low temperature hydrothermal conditions

Abstract

During low temperature hydrothermal alkaline conversion of kaolinite in the presence of sodium carbonate a disordered phase crystallizes showing structural features between the socialite and cancrinite minerals. A detailed study of its formation field and the kinetics of crystallization is the first step for fu~er investigations of this zenlite-like material. The crystallization kinetics was investigated in the early stage of the reaction for timesTul~, to 192 h at a temperature of 353 K. Besides X-ray powder diffraction A1 MAS NMR has been found to be the preferred method to follow the reaction kinetics because a signal assigned to six-coordinated almninium of the starting kaolinite can be clearly distinguished from a second resonance, being typical for aluminium in four-coordinate position of an aluminosilicate framework structure. Important conclusions can also be drawn from the experiments for the synthesis of ideal ordered cancrinites.

Nuclear magnetic resonance studies of aluminosilicate gels prepared in high-alkaline and salt-concentrated solutions

“…Previous syntheses of cancrinite and sodalite were carried out in a wide temperature range of 353-770 K with Si/Al P 1 under hydrothermal conditions [15][16][17][18][19]. No studies have been reported for the synthesis of cancrinite and sodalite under the conditions used in this study.…”

A statistical industrial approach for the synthesis conditions of zeolites using fly ash and kaolinite

“…In the majority of the studies, zeolite A and X were synthesized (Figure ). Forty‐eight studies were considered and analyzed with emphasis on the eight principal synthesized zeolites and six experimental factors .…”

Disordered but primitive gallosilicate hydro-sodalite: Structure and thermal behaviour of a framework with novel cation distribution

“…Fischer and Baur [1] gave a comprehensive overview on observed sodalite structures and their chemical composition. An alternative structural description via different stacking patterns of sheets of not connected (M 1 M 2 O4)3 six-ring sheets leads either to cancrinite (…AB… stacking in <001> direction), sodalite (…ABC… stacking in <111> direction) [2] or the so called intermediate phase with a distinct stacking disorder [3,4]. Generally, the resulting structures could be described in the cancrinite case in hexagonal space-groups (often 6 3 ) with lattice parameter a around 1260 pm and c around 520 pm in the aluminosilicate system (e.g.…”