Formation mechanism of CO₂ in the production of allyl acetate from propylene on PdCu(111) surface: A DFT study

Allyl acetate is an important organic chemical raw material and chemical intermediate. The gas-phase synthesis of allyl acetate from propylene is currently the most widely used process. So far, no researchers have reported the formation mechanism of CO2, the by-product that accounts for the most in the reaction process, which hinders the optimization of the catalyst and process. In this study, the combination of Density Functional Theory (DFT) and Kinetic Monte Carlo (kMC) was used to systematically study the formation mechanism of CO2 from propylene to allyl acetate over PdCu(111). The possible formation reaction network of CO2 in the reaction process was constructed. The calculation results showed that species are more easily adsorbed near the surface Pd atoms, and the adsorption sites of Pd-Cu bridge sites and fcc sites on PdCu(111) surface are more active. From the perspective of energy barrier, the acetic acid path tends to generate CO2 through chain scission and then dehydrogenation, while the propylene path produces CO2 through first dehydrogenation and then oxidative chain scission. Considering comprehensively, the two most likely paths to generate CO2 from propylene and acetic acid on PdCu(111) are: (1) CH3COOH -> CH3COO -> CH3(+CO2)-> CH2 -> CH -> C -> CO -> CO2, (2)CH3CHCH2 -> CH2CHCH2 -> CH2CHCH -> CH2CHC -> CHCHC -> CHCC -> CHCCO -> CHC(+CO)-> CHCO -> CO(+CH) -> CO2.