Dual modification of gallium‐doped Silicalite‐1 via alkaline treatment for exceptional methane to formic acid oxidation
Tiantian Liu, Baozhen Li, Xiaohua Li, Yanxi Liu, Manyu Ye, Xinli Ding, Xianfeng Yi, Yu Tang, Li Tan, Lizhi WuAbstract
The selective oxidation of methane to value‐added oxygenates under mild conditions is hindered by its inert C‐H bond and the over‐oxidation. Herein, we report a dual‐modification strategy combining gallium incorporation with alkaline hydrothermal treatment to enhance Fe dispersion and tailor acidity in a Silicalite‐1 zeolite. The resulting 0.5Fe/Ga‐S‐1‐Hydrothermal Treatment (HTS) catalyst delivers a formic acid (FA) yield of 58,851 μmol g cat −1 h −1 with 90.3% liquid‐product selectivity at 70°C using H 2 O 2 as the oxidant, cycling stability. Characterizations reveal that Ga doping promotes moderate acid sites, while alkaline treatment drives the redispersion of aggregated iron oxide clusters into dispersed, isolated extra‐framework Fe 3+ species, the key active centers. Electron paramagnetic resonance and in situ Fourier Transform Infrared Spectroscopy (FTIR) support a radical‐mediated pathway involving ·OH, ·OOH, and ·CH 3 intermediates drive the oxidation of methane to FA. This work demonstrates that integration of heteroatom doping and post‐synthetic treatment offers a platform for designing high‐performance zeolite catalysts for methane valorization.