Catalytic properties of Fe-HMS materials in the phenol oxidation

Iron-incorporated mesoporous silica material Fe-HMS-50 (the Si/Fe molar ratio in the precursor gel is 50) was synthesized at ambient temperature by using hexadecylamine as a template and characterized by chemical analysis and N₂ adsorption measurements. The catalytic performance of Fe-HMS was studied in the phenol hydroxylation and wet phenol oxidation with H₂O₂ at 313 K. The effect of pH, H₂O₂: PhOH molar ratio and stability of the catalyst on the oxidation process was investigated. In the phenol oxidation, the activity of the catalyst increases by increasing the acidity of the reaction mixture to pH 3.4 and the amount of leached iron species was 1.95 ppm. A recycling test indicates that the catalyst recovered by drying in air at 423 K suffered, after the first run, a 12.4% drop in the catalytic activity. Fe-HMS has high catalytic activity and selectivity to dihydroxybenzene in the phenol hydroxylation. Hydroquinone was found as the predominant product under these experimental conditions with small amounts of benzoquinone appearing at the end of the reaction.