Highly Selective Oxidation of Methane into Methanol over Cu-Promoted Monomeric Fe/ZSM-5

Abstract

The selective oxidation of methane into methanol is of paramount importance but poses significant challenges in achieving high methanol productivity and selectivity, especially under mild reaction conditions. We show that a Cu-modified monomeric Fe/ZSM-5 catalyst is a highly efficient material for the direct conversion of methane into methanol in the liquid phase using H2O2 as an oxidant at low temperatures, which exhibits an excellent methanol productivity of 431 molMeOH·mol–1Fe·h–1 (with a methanol selectivity of ∼80% over the Cu-Fe(2/0.1)/ZSM-5 catalyst). Combining the control experiments and comprehensive characterization results by among others, Mössbauer spectroscopy, and electron paramagnetic resonance as well as density functional theory calculations, we found that Cu species in the Cu-Fe(2/0.1)/ZSM-5 catalyst play a pivotal role in facilitating the formation of •OH radicals, which quickly react with •CH3 radicals to form CH3OH. These findings provide valuable insights into the rational design of metal–zeolite combinations for the selective oxidation of methane into methanol.