Croatica Chemica Acta, Vol. 76 No. 1, 2003.
Original scientific paper
Influence of Silica Sources on the Chemical Composition of Aluminosilicate Hydrogels and the Results of Their Hydrothermal Treatment
Ivan Krznarić
; Laboratory for the Synthesis of New Materials, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
Tatjana Antonić
; Laboratory for the Synthesis of New Materials, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
Josip Bronić
orcid.org/0000-0001-5846-0235
; Laboratory for the Synthesis of New Materials, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
Boris Subotić
orcid.org/0000-0002-3589-7845
; Laboratory for the Synthesis of New Materials, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
Robert W. Thompson
; Department of Chemical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
Abstract
Among the parameters that influence the outcome of a hydrothermal synthesis of molecular sieve zeolites, the effects of various silica sources are some of the least understood. Prior studies have noted that some silica sources were »active,« or »inactive,« and there have been some suggestions that aluminium impurities can contribute to a silica source’s »activity« to promote certain zeolite syntheses. However, a silica source’s activity toward promoting zeolite crystallization has not been definitively shown to be linked to any specific impurity in the silica. This study reports on the use of four different silica sources and the corresponding distribution of Na, Al, and Si between the supernatant and amorphous gel phases. It is shown that the distribution of these species was unaffected by the choice of the silica source, but did vary with batch composition. Furthermore, the degree of silicate polycondensation (DPS), measured by the molybdate method, did not vary with the choice of the silica source. The observed differences in particulate and structural properties of the products crystallized from four different silica sources were analyzed in terms of the critical processes of zeolite crystallization (gel dissolution, nucleation, crystal growth).
Keywords
aluminosilicate gels; precipitation; silica source; chemical composition; hydrothermal treatment; zeolite; crystal size
Hrčak ID:
103052
URI
Publication date:
30.4.2003.
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