1
10
W. Turek, A. Krowiak / Applied Catalysis A: General 417–418 (2012) 102–110
of propene according to E1cB mechanism and dehydrogenation to
acetone).
Therefore, the possibility of dehydration of isopropyl alcohol to
diisopropyl ether is determined by the distance between adjacent
cations, their accessibility for reactants and acidity.
catalyst contains Brønsted acid centres, the reaction products
are mainly propene and diisopropyl ether. If the catalyst con-
tains redox centres and it does not contain Brønsted acid centres,
the main reaction product is acetone. For catalysts with Lewis
acid and basic centres the amounts of propene and acetone are
similar.
4
. Conclusions
7) The conditions of diisopropyl ether formation over Lewis acid
centres were determined. The possibility of this reaction is
determined by:
The results presented above show that the test reaction of iso-
propyl alcohol conversion can be used not only to determine the
type of centres over which the reaction proceeds, but also to eval-
uate the strength of active centres.
- the distance between adjacent cations (Lewis acid centres). If the
distance is higher, the probability of dehydration to diisopropyl
ether decreases,
1
) It was demonstrated that Brønsted and Lewis acid centres in
oxide catalysts can be distinguished on the basis of catalytic
activity in the reaction of dehydration to propene. It is possi-
ble because the dehydration to propene proceeds over Brønsted
acid centres according to a different mechanism than over Lewis
acid centres. As a result the rate of reaction over Brønsted acid
centres is significant at lower temperatures than over Lewis acid
centres.
) It was also found that the rate of dehydration to propene is a
measure of the strength of acid and basic centres participating
in the reaction. In the case of catalysts with Lewis acid centres
the rate of dehydration increases when the strength of basic cen-
tres is higher. In the case of catalysts with Brønsted acid centres
the rate of dehydration increases with the strength of acid cen-
tres. It is important that the evaluation of the strength of Lewis
and Brønsted acid centres on the basis of the rate of dehydration
to propene does not depend on the amount of formed propene,
therefore it is independent of the number of active centres par-
ticipating in the reaction.
- accessibility of the centres for the substrate (isopropyl alcohol),
and
- strength of acid centres and adjacent basic centres, which can
interact with alcohol molecules chemisorbed at acid centres and
direct its transformation to propene or acetone.
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