The complete catalytic oxidation of ethylene at low temperatures is of great significance for the preservation of agricultural products during transportation. Au-based catalysts with various Pd ensembles have recently shown promise in catalytic oxidation. In this work, the catalytic mechanisms and energetics for ethylene oxidation on a PdAu bimetallic catalyst with a second neighboring Pd configuration were systematically investigated from a theoretical perspective. It is found that the PdAu bimetallic catalyst can produce seven adsorption sites for ethylene oxidation. The entire reaction network consists of four processes: C–O bond formation, C–C bond cleavage, CO2 formation, and H2O formation, which involve a total of 21 adsorbed species and 35 elementary reactions. Among the several possible oxygenates, CH2CO is an important intermediate and has the lowest energy barrier of the C–C bond cleavage. The second neighboring Pd configuration makes O active in C–O bond formation. Finally, the most energetically favorable pathway of complete ethylene oxidation was determined as CH2CH2 → CH2CH2O­(OME) → CH2CHO → CH2CO → CH2 → CH → CHO → CO → CO2. In all, the PdAu bimetallic catalyst shows high activity for the complete oxidation of ethylene. We hope that this comprehensive work can provide a deeper understanding of the hydrocarbon oxidation on bimetallic catalysts.

The soot emission during fuel pyrolysis is harmful to the human health, environment, and engine fuel efficiency. In this work, the effect of methanol addition on soot inhibition of n-decane pyrolysis was investigated both theoretically and experimentally. Thermal cracking and coking experiments of n-decane show that the coke mass decreases significantly with methanol addition. Molecular dynamics (MD) simulations indicate that the oxidative radicals (OH, HCO, and CH2OH) from the methanol additive will oxidize the key precursors (such as C2H2, C3H3, and C5H5) of polycyclic aromatic hydrocarbons (PAHs) to stable oxides. Six key reactions were determined and found to play a key role in inhibiting the soot formation. The corresponding kinetic parameters were calculated at the CCSD­(T)/CBS level for kinetic simulations by adding to the CRECK model. The simulation results show that the mole fractions of C2H2, C3H3, C5H5, and BINs decrease significantly with methanol addition. It indicates that the methanol addition can inhibit the soot formation, which is in good agreement with the experimental findings. We hope that this comprehensive work can provide significant information for soot inhibition.

No abstract