Crystallization kinetics of Na7.4(AlSiO4)6(CO3)0.7·4H2O, an intermediate phase between cancrinite and sodalite, grown under low temperature hydrothermal conditions |
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Authors: | Karsten Hackbarth Michael Fechtelkord and Josef-Christian Buhl |
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Institution: | (1) Henkel KGaA, Düsseldorf;(2) Institut für Mineralogie der Universit?t Hannover, Welfengarten 1, 30167 Hannover |
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Abstract: | During low temperature hydrothermal alkaline conversion of kaolinite in the presence of sodium carbonate a disordered phase
crystallizes showing structural features between the sodalite and cancrinite minerals. A detailed study of its formation field
and the kinetics of crystallization is the first step for further investigations of this zeolite-like material. The crystallization
kinetics was investigated in the early stage of the reaction for times up to 192 h at a temperature of 353 K. Besides X-ray
powder diffraction27Al MAS NMR has been found to be the preferred method to follow the reaction kinetics because a signal assigned to six-coordinated
aluminium 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. |
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Keywords: | Cancrinites Sodalites disordered aluminosilicates crystallization kinetics MAS NMR |
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