A series of Fe-silicalites with MFI structure, employed as catalysts in the
title reaction, was investigated by FTIR analysis, using pyridine as the p
robe molecule for acidity determination. The oxidation reaction was also mo
nitored by FTIR spectroscopy on the best-performing catalyst. An optimal co
ntent and distribution of extra-framework iron assures high selectivity, wh
ile high acidity increases benzene conversion, but lowers the phenol yield.
Benzene conversion to phenol occurs on N2O-pretreated Fe-silicalite cataly
sts only and N2O does not adsorb as such on the catalyst, even at low tempe
rature, but undergoes decomposition: this confirms the activating role of N
2O in the reaction mechanism. Under the experimental conditions adopted in
reaction monitoring, the yield of adsorbed phenol is maximal around 550 K a
nd the reaction is paralleled by the complete oxidation of benzene to CO2.