A simple and efficient zeolite catalyst for toluene oxidation in aqueous media

In this work, it was found that alkali-treated zeolites could efficiently catalyze oxidation of toluene with H2O2 in aqueous media. No heavy metals or their oxides were employed in the synthesis of catalyst and no additives were used in this catalytic system. Through optimizing the experimental conditions, alkali-treated HZSM-5 exhibited good catalytic activity for toluene oxidation in only 5 h at a low temperature (below 100 °C): 32.0% conversion of toluene with selective formation of 25.0% benzaldehyde, 20.8% benzyl alcohol and 27.5% benzoic acid. Moreover, the results of reusability studies indicated that alkali-treated HZSM-5 was a durable and green catalyst for toluene oxidation in aqueous media. The changes in acidities and textural features of the zeolites induced by alkali-treatment were characterized by ammonia temperature programmed desorption (NH3-TPD) and X-ray powder diffraction (XRD), respectively. The results indicated the reactivity for toluene oxidation could be related to the amount of species Al and AlOH in this system. A probable redox mechanism for toluene oxidation catalyzed by alkali-treated zeolites in aqueous media was proposed in this work.

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► Alkali-treated zeolites showed good catalytic activity for toluene oxidation.
► Pure water was firstly used as the sole medium for toluene oxidation.
► No heavy metals or their oxides were employed in this catalytic system.
► A probable redox mechanism for toluene oxidation in water media was firstly proposed.
► This heterogeneous catalytic process is environment-friendly.