One-pot synthesis of highly active Fe-containing MWW zeolite catalyst: Elucidation of Fe species and its impact on catalytic performance

Fe-containing MWW zeolite catalysts in the absence (Fe-MWW) or presence of Al atoms (Fe,Al-MWW) were directly prepared by the hydrothermal synthesis approach. The nature of Fe species was systematically analyzed by UV–vis, in-situ NO adsorption FTIR spectroscopy, and H₂-TPR technology. The presence of Al atoms in the synthesis gel seriously affected the chemical composition, textural properties, and the states of Fe species, hence made the catalytic activity in hydroxylation of benzene with H₂O₂ worse than the one without Al. Moreover, we found that the states of Fe species could be adjusted by changing the calcination temperature. The catalytic activity of Fe-MWW was improved by increasing the calcination temperature, while that of Fe,Al-MWW was weakened due to the degeneration of texture properties and the transformation of Fe species. Fe-MWW zeolite calcined at 750 °C exhibited the highest 8.3% yield and 94% selectivity to phenol in direct hydroxylation of benzene with H₂O₂.