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Kinetic analysis of non-isothermal transformation of zeolite 4A into low-carnegieite

Kosanović, Cleo; Subotić, Boris; Ristić, Alenka; Sekovanić, Lavoslav (2004) Kinetic analysis of non-isothermal transformation of zeolite 4A into low-carnegieite. Croatica Chemica Acta, 77 (4). pp. 553-560. ISSN 0011-1643

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Abstract

Kinetics of the non-isothermal transformation of zeolite 4A to low-carnegieite was investigated by the X-ray diffraction method. Changes in the fractions of zeolite 4A, amorphous aluminosilicate and low-carnegieite during zeolite 4A heating at three different heating rates (0.0833 degrees S-1, 0.1667 degrees s(-1) and 0.333 degrees s(-1)) showed that amorphization of zeolite 4A and crystallization of low-carnegieite take place simultaneously. Kinetic analyses of amorphization and crystallization showed that the non-isothermal transformation took place by the same mechanism as the isothermal transformation, i.e., amorphization of zeolite 4A proceeded by a random, diffusion-limited agglomeration of the short-range ordered aluminosilicate subunits formed by the thermally induced breaking of Si-O-Si and Si-O-Al bonds between different building units of zeolite framework. Crystallization of low-carnegieite occurred by homogeneous nucleation of low-carnegieite inside the matrix of amorphous aluminosilicate and was diffusion-control led, with one-dimensional growth of the nuclei. Kinetics of non-isothermal processes was determined by the changes of the rate constants during heating and the apparent activation energies of amorphization and crystallization.

Item Type: Article
Uncontrolled Keywords: non-isothermal transformation; zeolite 4A; amorphous aluminosilicate; low carnegieite; kinetics; mechanism; mullite reaction sequence; x-ray-diffraction; crystallization kinetics; phase-transformations; synthetic mordenite; thermal-treatment; na-a; nucleation; equations; ceramics
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Division of Materials Chemistry
Projects:
Project titleProject leaderProject codeProject type
Istraživanje procesa kristalizacije i primjene zeolitaBoris Subotić0098060MZOS
Depositing User: Boris Subotić
Date Deposited: 08 Nov 2013 11:26
Last Modified: 26 Feb 2014 11:42
URI: http://fulir.irb.hr/id/eprint/906

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