Abstract
The crystallization of Sn-Beta in
fl
uoride medium is greatly in
fl
uenced by the amount and type of tin source
present in the synthesis gel. By varying the amount of tin in the form of tin(
IV
) chloride pentahydrate, the time
required for crystallization was studied. It was found that tin not only drastically a
ff
ects the time required for
crystallization, but also that the presence of tin changes the morphology of the formed Sn-Beta crystals. For
low amounts of tin (Si/Sn
¼
400) crystallization occurs within four days and the Sn-Beta crystals are capped
bipyramidal in shape, whereas for high amounts of tin (Si/Sn
¼
100) it takes about sixty days to reach full
crystallinity and the resulting crystals are highly truncated, almost plate-like in shape. Using SEM-WDS to
investigate the tin distribution along transverse sections of the Sn-Beta crystals, a gradient distribution of
tin was found in all cases. It was observed that the tin density in the outer parts of the Sn-Beta crystals is
roughly twice as high as in the tin depleted core of the crystals. Sn-Beta was found to obtain its
maximum catalytic activity for the conversion of dihydroxyacetone to methyl lactate close to the
minimum time required for obtaining full crystallinity. At excessive crystallization times, the catalytic
activity decreased, presumably due to Ostwald ripening
Original language | English |
---|---|
Journal | Journal of Materials Chemistry A |
Volume | 2 |
Issue number | 47 |
Pages (from-to) | 20252-20262 |
ISSN | 2050-7488 |
DOIs | |
Publication status | Published - 2014 |