Enhancing catalytic activity of Cr2O3 in CO2-assisted propane dehydrogenation with effective dopant engineering: a DFT-based microkinetic simulation

Abstract

Using CO₂ as a mild oxidizing agent in propane dehydrogenation (PDH) presents an attractive pathway for the generation of propene while maintaining high selectivity. Cr₂O₃ is one of the most important catalysts used for the CO₂-assisted PDH process. In this study, the doping of Cr₂O₃ with single atoms such as Ge, Ir, Ni, Sn, Zn, and Zr was used for the PDH process. The introduction of dopants significantly modifies the electronic structure of pristine Cr₂O₃, leading to substantial alterations in its catalytic capabilities. The dehydrogenation reactions were explored both in the absence and presence of CO₂. The addition of CO₂ introduces two distinct pathways for PDH. On physisorbed CO₂ surfaces, Ge and Ni–Cr₂O₃ enhance dehydrogenation. On the dissociated surface, the CO* and O* species actively participate in the reaction. All doped surfaces exhibit low energy barriers for dehydrogenation, except undoped Cr₂O₃ on dissociated CO₂ surfaces. The Ni–Cr₂O₃ surface emerges as the most active surface for dehydrogenation of propane in all scenarios. Additionally, the catalytic surface is re-oxidized through H₂ release, and doped surfaces facilitate coke removal via the reverse Boudouard reaction more efficiently than undoped Cr₂O₃. Microkinetics simulations identify the removal of the first H-atom as the rate-determining step. CO₂ reduces the apparent activation energy, directly impacting C₃H₈ conversion and C₃H₆ formation. This study offers a decisive description of Cr₂O₃ modification for the CO₂-assisted PDH process.