Journal
CROATICA CHEMICA ACTA
Volume 85, Issue 3, Pages 297-301Publisher
CROATIAN CHEMICAL SOC
DOI: 10.5562/cca2055
Keywords
zeolite A; autocatalytic nucleation; crystal size distribution; hydrogel ageing
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Funding
- Ministry of Science, Education and Sport of Republic of Croatia [098-0982904-2953]
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Zeolites are crystalline, microporous, alumo-silicate materials (around 400 types) which are used in many applications. Each field of usage (catalysis, ion exchange, sorption, molecular sieving, etc.) has demands regarding crystals' structural and particulate properties. Detailed understanding of the mechanisms of crystals' formation and growth enables the control of these properties. Hydrogels of the starting composition 3.2 Na2O x 2 SiO2 x 1.05 Al2O3 x 250 H2O were heated in stainless steel reactor at 80 degrees C under dynamic conditions, after ageing for t(A) = 0-209 h at 25 degrees C. Solid phase samples were characterized using microscopy (OM, SEM), PXRD and laser light scattering (LLS). Specific number of zeolite A crystals was calculated from particle size distributions. It was shown that the some particulate properties: specific number of crystals and crystal size distribution, are changing towards higher number of crystals and wider size distribution while the morphology of the crystals remains the same. Also, the crystal growth rate is higher in the systems which are treated under dynamic conditions. Obtained results were compared with data of systems crystallized under static conditions and commented on the grounds of the autocatalytic nucleation theory. (doi: 10.5562/cca2055)
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