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

2021 
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.
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