The mechanism of CO coupling reaction to form dimethyl oxalate over Pd/α-Al2O3

The purpose of this study is to investigate the mechanism of CO coupling reaction to form dimethyl oxalate (DMO) over Pd/α-Al2O3 by using in situ infrared spectroscopy. The formation of DMO is initiated by methyl nitrite (MN) adsorption and CO adsorption over Pd/α-Al2O3. Two intermediates, ON–Pd–OCH3 and ON–Pd–COOCH3, were identified. The formation of DMO proceeds via coupling two ON–Pd–COOCH3 intermediates. CO adsorption generates linearly bonded CO and bridge bonded CO over Pd/α-Al2O3, but only bridge bonded CO participates in the reaction. Moreover, the ratio of ON–Pd–OCH3 to bridge bonded CO over Pd/α-Al2O3 surface has significant influence on the formations of by-products (methyl formate (MF) and dimethyl carbonate (DMC)).

The formation of dimethyl oxalate (DMO) is initiated by adsorptions of methyl nitrite (MN) and CO. Adsorbed species of reactants participated in the reaction are ON–Pd–OCH3 and bridge bonded CO. The formation of by-product dimethyl carbonate (DMC) is suppressed when the ratio of ON–Pd–OCH3 to bridge bonded CO over catalysts surface is low.Figure optionsDownload as PowerPoint slide