Abstract: The reaction mechanism of CO coupling to dimethyl oxalate over Pd/α-Al2O3 was studied by in situ FT-IR spectroscopy. The adsorption of two reactants, CO and methyl nitrite, on the catalyst was observed. Methyl nitrite can easily catalytically dissociate into methanol, formaldehyde, and methyl formate. By changing the addition sequence of the two reactants into the in situ reactor, the process of the coupling reaction was clearly observed. The results show that bridged adsorbed CO reacts with free methyl nitrite gas, and the key step of the whole reaction is the CO adsorption.

Key words: carbon monoxide, bridged adsorption, methyl nitrite, coupling, dimethyl oxalate, palladium, reaction mechanism, Fourier transform infrared spectroscopy