Kosanović, Cleo; Subotić, Boris; Ristić, Alenka; Sekovanić, Lavoslav
Kinetic analysis of non-isothermal transformation of zeolite 4A into low-carnegieite.
Croatica Chemica Acta, 77
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.
||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
||NATURAL SCIENCES > Chemistry
||Division of Materials Chemistry
|Project title||Project leader||Project code||Project type|
|Istraživanje procesa kristalizacije i primjene zeolita||Boris Subotić||0098060||MZOS|
||08 Nov 2013 11:26
||26 Feb 2014 11:42
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