Activity of H-Beta Zeolites Re-Exchanged with Alkaline and Earth-Alkaline Cations in the Fries Rearrangement of Phenyl Acetate

The heterogeneously catalysed liquid phase Fries rearrangement reaction of phenyl acetate was carried out on Beta zeolites re-exchanged with different amounts of metal cations. The aim of this work was to determine the influence of the amount of Brönsted acid sites as the catalytic active centres on the conversion and to study differences in their acidic strength. Sodium and potassium ions as well as bivalent calcium and zinc ions were used in the reexchange procedure. The conversion shows a linear dependency on the degree of ion re- exchange following the theoretically expected values. So the results proof that the bridged hydroxyl groups are indeed the dominating active centres and that their strength seems to be independent on the degree of reexchange. A special emphasis was placed on the re-exchange with bivalent metal ions. It was shown that one bivalent ion is not able to replace two protons as supposed to be necessary for the charge balance - so a 1:1 stoichiometry is needed to assume to explain the catalytic results.