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Modification of structural and acidic properties of sol–gel-prepared alumina powders by changing the hydrolysis ratio
Ist Teil von
Applied catalysis. A, General, 2003-02, Vol.241 (1), p.319-329
Ort / Verlag
Amsterdam: Elsevier B.V
Erscheinungsjahr
2003
Link zum Volltext
Quelle
Elsevier ScienceDirect Journals Complete
Beschreibungen/Notizen
The structural and acidic properties of sol–gel prepared alumina powders as catalyst supports were modified by adjusting the hydrolysis ratio,
R (i.e. molar ratio of water relative to the alumina precursor,
R=[H
2O]/[aluminium-tri-sec-butoxide (ASB)]). Structural properties (e.g. porosity) and acidic properties were measured for alumina powders prepared with various
R values, from 3 to 13. For
R<9 and
R>10, first-order particles were closely packed with ink-bottle-type pore structures, whereas for
R=9 or 10, first-order particles were loosely packed with a spatial fractal arrangement that yielded pseudo-cylindrical pore structures. In addition, the alumina powders prepared with
R=9 or 10 had larger water pore volume and stronger acidity than those with other
R values. These properties unique to the powders prepared with
R=9 or 10 were ascribed to relatively short Al–O–Al chain lengths that resulted in loose packing of first-order particles. The results here indicate that alumina powders with favorable properties as catalyst supports (e.g. mean pore diameter) can be tailored by selecting the appropriate
R in the sol–gel synthesis process.