Abstract
The synthesis of zeolite Nu-10 was investigated in the presence of alkali chlorides and tetraethylenepentamine (TEPA) or 1,3-diaminopropane (DAP) as organic structure-directing agents. By means of 13 C CP MAS NMR spectroscopy it was possible to identify in each case the nature of the organic species occluded in the channel system of the as-synthesized zeolite. TEPA is incorporated intact in its di- or tri-protonated form, depending on the Al content of the initial hydrogel. DAP is occluded in its mono-protonated form together with n-propylamine, di- n-propylamine and pyridine, these latter stemming from a prompt decomposition of DAP during the synthesis. This decomposition can be strongly affected by the synthesis temperature; the organic intermediates so formed can readily favor the formation of other types of zeolite structures and hence completely re-orient the synthesis route. Structural SiO − defect groups, neutralizing the excess of positive charges, are created together with terminal SiOH groups. Their relative amounts were determined using chemical and thermal analysis combined with 29 Si NMR data.
Published Version
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