Highly Efficient Conversion of Methane to Methanol on Fe-Cu/ZSM-5 Under Mild Conditions: Effective Utilization of Free Radicals by Favorable Valence Ratios

Abstract

The selective oxidation of methane to methanol under mild conditions remains a significant challenge due to its stable C-H bond and the propensity for overoxidation of products. Herein, we investigated the Fe- and Cu-modified ZSM-5 catalysts using H2O2 as an oxidant for the selective oxidation of methane. It was found that the Fe/Cu ratio had a great impact on methanol yield. The Fe3Cu1 displayed the highest methanol yield of 29.7 mmol gcat−1 h−1 with a selectivity of 80.9% at 70 °C. Further analysis revealed that Fe3Cu1 showed the highest Fe3+ and Cu+ contents. The optimal dual valence cycle not only facilitates the efficient utilization of H2O2, promoting the activation of methane to •CH3 at the Fe site, but also suppresses the deep oxidation caused by the Fenton-like effect of Fe/H2O2, thus maintaining the high yield and high selectivity of methanol.