Tuning the Lewis acidity of ZrO2 for efficient conversion of CH4 and CO2 into acetic acid

Abstract

The conversion of CH₄ and CO₂ into acetic acid is a dream reaction, but it remains a great challenge owing to the inertness of both CH₄ and CO₂. The formation of acetic acid requires efficient activation of CH₄ and CO₂. In this work, we demonstrated that enhanced acetic acid production from CH₄ and CO₂ is achieved via improving the Lewis acidity of ZrO₂-containing catalysts. Definitely, the best catalyst (SZ-3) exhibits about 14 times higher activity for acetic acid formation than that of pure ZrO₂, owing to its strongest Lewis acidity that facilitates the activation of both CH₄ and CO₂. The mechanism of acetic acid formation is revealed via DFT calculations. CH₄ is activated at Lewis acid sites to form Zr–CH₃ and O–H species, and subsequently, the O–H species could readily hydrogenate CO₃ species formed from CO₂ activation at Lewis acid sites to give HCO₃, followed by facile coupling with Zr–CH₃ yielding acetic acid with a lower energy barrier.