Catalytic Activity of Fe(III)-substituted aluminophosphate molecular sieves in oxidation of aromatic compounds

Many metal-containing microporous zeolites have been used in heterogeneous catalytic reactions since TS-1 zeolite used as a catalyst in oxidation reactions. To obtain new catalysts with relatively simple procedures of preparation, iron-substituted aluminophosphate molecular sieves (FeAlPO₄-5, FeAlPO₄-11 and FeVPI-5, denoted as Fe(III)APO) were hydrothermally synthesized. These samples were catalytically active in oxidation of aromatic compounds, e.g., hydroxylation of phenol and benzene, epoxidation of styrene, and oxidation of naphthol. The catalytic activity of FeAlPO₄-5 and FeAlPO₄-11 was comparable with that of TS-1 in some reactions. In hydroxylation of phenol and benzene, FeAlPO₄-11 could give conversion of 22.1 and 13.1%, respectively. In styrene epoxidation, FeAlPO₄-11 achieved conversion of 24.7% and selectivity of 55.2%, while TS-1 gave selectivity of 6.2% only, suggesting that the reaction routes in styrene epoxidation are different over these two catalysts. FeVPI-5 is a good candidate for the catalytic oxidation of large organic compounds.