Probing the structure sensitivity of dimethyl oxalate partial hydrogenation over Ag nanoparticles: A combined experimental and microkinetic study.

The finding that the MG selectivity increases and the DMO hydrogenation activity decreases with increasing the Ag nanoparticle size reveals the structure sensitivity of DMO partial hydrogenation. [Display omitted] • The structural sensitivity of DMO partial hydrogenation over Ag catalysts. • Ag stepped surfaces dominate the kinetics of the hydrogenation reaction. • The DMO consumption rate decreases with increasing the nanoparticle size. • The MG selectivity rises as the particle size changes from 5 nm to 10 nm. • A new strategy to ensure thermodynamic consistency of the reaction. Silver nanoparticles of different sizes have been synthesized to study their catalytic performance in dimethyl oxalate (DMO) partial hydrogenation to methyl glycolate (MG). Then, a detailed microkinetic analysis based on the results of DFT calculations has been performed to elucidate the origin of the observed size-dependent kinetics, where tabulated thermodynamic properties of gas-phase species are used to ensure the thermodynamic consistency of the reaction. Calculated results show that the turnover frequency for DMO consumption is much higher on Ag(2 1 1) than on Ag(1 1 1), suggesting the stepped surface dominates the kinetics. The hydrogenation of DMO on the two surfaces occurs along the same dominant reaction pathway, and the rate-determining step for the partial and deep hydrogenation of DMO is DMO and MG dissociation, respectively. The finding that the MG selectivity increases while the DMO hydrogenation activity decreases with the Ag nanoparticle size reveals the structure sensitivity of DMO partial hydrogenation. [ABSTRACT FROM AUTHOR]