Ethylene carbonate generated efficiently via ethylene oxide and CO2 on the Li-MgO(1 0 0) surface based on the synergistic activation of bimetals without halogen

Abstract

The cycloaddition of ethylene oxide (EO) and CO2 to generate ethylene carbonate (EC) is an atom-efficient process in which halogen-containing catalysts perform admirably. However, the trace halogen frequently remains in EC, making it unsuitable for further use. Exploring a halogen-free catalyst for EC formation is thus an interesting and meaningful work. A gas–solid reaction with magnesium oxide catalyst has been designed and its performance has also been investigated by the density functional theory calculation (DFT). Pure MgO exhibits low activity for the cycloaddition of EO and CO2 due to high activation energy with 278.1 kJ⋅mol−1 to yield EC. A stable Li-MgO catalyst was obtained via ab initio molecular dynamics simulations (AIMD), and various reaction mechanisms were observed. Both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms for the EC formation exist. However, the most conductive energy path to generate EC is a one-step route via the E-R mechanism with an activation energy of only 39.8 kJ⋅mol−1. And the selectivity of EC can be increased significantly when the temperature exceeds 673 K. Based on the Bader charge and crystal orbital Hamilton populations (COHP) analysis, the bimetals of Li and Mg serve as the active site in Li-MgO catalyst, which replaces the role of halogen in traditional catalysts to activate EO synergistically for generating EC. Furthermore, the prediction of Fourier transform infrared spectroscopy (FTIR) of catalysts can be a valuable reference for the design of green and sustainable catalysts.