Synthesis of recyclable catalyst–sorbent Fe/CMK-3 for dry oxidation of phenol

The magnetic mesoporous material Fe/CMK-3 acting as a catalyst–sorbent was synthesized by using ordered mesoporous carbon CMK-3 as the supporter, Fe(NO3)3 as the iron source, and glycol as the reducing agent. The samples synthesized were characterized by powder X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results show that the prepared Fe/CMK-3 preserved the ordered mesoporous structure of CMK-3, and magnetic species was mainly Fe3O4, which was dispersed inside channels of CMK-3 as nanoparticles with the diameter of around 10 nm. The adsorption and catalytic dry oxidation efficiency of the prepared Fe/CMK-3 were determined. The results also show that Fe/CMK-3 had good adsorption performance of phenol in aqueous solution and could be easily separated from water and recycled due to its ferromagnetic nature. Iron oxides supported on CMK-3 were excellent catalysts for dry oxidation of phenol. After 15 adsorption–catalytic oxidation cycles, the phenol adsorption capacity of Fe/CMK-3 only decreased a little, suggesting the good practicality. Combined thermogravimetry and mass spectrum (TG–MS) instrument was used to investigate the catalytic oxidation of phenol on Fe/CMK-3 and the ignition characteristics of the catalyst–sorbent. The supported Fe3O4 was found to be not only the magnetic component but also the active catalyst for the oxidation of phenol. The adsorbed phenol could be oxidized into CO2 and H2O at 220 °C at which no obvious phenol desorption or CMK-3 ignition occurred.

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► Fe3O4 is the main magnetic species inside channels of CMK-3.
► Fe/CMK-3 exhibits excellent operational stability for dry oxidation of phenol.
► The adsorbed phenol can be oxidized into CO2 and H2O at 220 °C.
► Fe/CMK-3 can be easily separated from water and recycled due to its ferromagnetic nature.