Synthesis, characterization and catalytic performance for phenol hydroxylation of Fe-MCM41 with high iron content

A series of Fe-MCM41s with different iron content have been synthesized and characterized by XRD, BET, HRTEM, FT-IR, UV-vis and ICP techniques. Their catalytic performances for the direct hydroxylation of phenol were also studied. Results indicated that the mesoporous structure did not collapse until the Fe/Si molar ratio reached up to 0.20. The iron species were mainly in the framework with isolated tetrahedral coordination as Fe/Si molar ratio was smaller than 0.091 and micro-crystals of Fe₂O₃ were detected when iron content increased further. The prepared samples exhibited excellent catalytic activities for the direct hydroxylation of phenol by hydrogen peroxide at room temperature, which increased with iron content in the framework of MCM41 and did not decline after being recycled 6 times. As Fe/Si molar ratio increased to more than 0.091, the catalytic activity decreased gradually with iron content due to the covering of some active sites, i.e., the incorporated iron species with tetrahedral coordination, by the accumulated Fe₂O₃ on the surface of the catalyst.