A theoretical study on the mechanism of conversion of C3H8 and CO2 to C3H6 and HCOOH by M4–B24N28 catalysis

Abstract

The mechanism of the conversion of propane and carbon dioxide to propylene and formic acid on the M₄–B₂₄N₂₈ (M = V, Cr, Ni, Cu) surface was studied based on density functional theory (DFT). Through the preliminary calculation of propane oxidation, it was found that Cu₄–B₂₄N₂₈ has relatively good catalytic activity. After that, all possible paths for the oxidation reaction of propane and carbon dioxide on the surface of Cu₄–B₂₄N₂₈ were calculated in detail. The calculation results showed that the optimal path is the dehydrogenation of the secondary carbon of propane combined with the carbon atoms of carbon dioxide to form a HCO₂ intermediate, and then the secondary carbon continues to dehydrogenate to combine with the HCO₂ intermediate to form a C₃H₆ intermediate and formic acid. After that the hydrogen atom of the primary carbon of the C₃H₆ intermediate is rearranged to the secondary carbon to produce propylene (CH₃CH₂CH₃ + CO₂ → CH₃CHCH₃ + OCHO → CH₃CCH₃ + HCOOH → CH₂CHCH₃ + HCOOH), the rate control step of the reaction process is the rearrangement of the hydrogen atom of the C₃H₆ intermediate, and then formic acid and propylene are desorbed with desorption energies of −0.23 eV and −0.50 eV respectively, and can be further recycled. In summary, Cu₄–B₂₄N₂₈ can be used as an effective catalyst for the oxidation of propane by carbon dioxide, which can maintain the catalytic activity and take into account the catalytic stability without generating carbon deposits.