Highly efficient oxidation of methane into methanol over Ni-promoted Cu/ZSM-5†

Direct functionalization of methane in natural gas is of paramount importance but faces tremendous challenges. We reported a nickel-modified copper zeolite catalyst for the selective oxidation of methane into methanol. Using H₂O₂ as an oxidant in the liquid phase at 80 °C, Cu₁Ni_0.75/ZSM-5 catalyst presented a relatively high methanol yield of 82 162 μmol g_cat⁻¹ h⁻¹ (with a methanol selectivity of ∼74%). Combining series of designed experiments and thorough characterization analysis, including electron microscopy, X-ray photoelectric spectroscopy, Fourier transform infrared reflection as well as in situ diffuse reflectance infrared Fourier transform spectroscopy, abundant Cu^I active sites were found on Ni-Promoted Cu/ZSM-5, differing from the dominating Cu^II active sites over Cu/ZSM-5. Cu^I active sites had an excellent ability to promote CH₄ adsorption, CH₄ activation and CH₃OH generation compared to Cu^II active sites. This work elucidates a constellation of insightful and potent perspectives for further improvement of metal-zeolite catalysts for the direct oxidation of methane to methanol.