Enhancing catalytic activity of Cr 2 O 3 in CO 2 -assisted propane dehydrogenation with effective dopant engineering: a DFT-based microkinetic simulation.

Using CO 2 as a mild oxidizing agent in propane dehydrogenation (PDH) presents an attractive pathway for the generation of propene while maintaining high selectivity. Cr 2 O 3 is one of the most important catalysts used for the CO 2 -assisted PDH process. In this study, the doping of Cr 2 O 3 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 Cr 2 O 3 , leading to substantial alterations in its catalytic capabilities. The dehydrogenation reactions were explored both in the absence and presence of CO 2 . The addition of CO 2 introduces two distinct pathways for PDH. On physisorbed CO 2 surfaces, Ge and Ni-Cr 2 O 3 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 Cr 2 O 3 on dissociated CO 2 surfaces. The Ni-Cr 2 O 3 surface emerges as the most active surface for dehydrogenation of propane in all scenarios. Additionally, the catalytic surface is re-oxidized through H 2 release, and doped surfaces facilitate coke removal via the reverse Boudouard reaction more efficiently than undoped Cr 2 O 3 . Microkinetics simulations identify the removal of the first H-atom as the rate-determining step. CO 2 reduces the apparent activation energy, directly impacting C 3 H 8 conversion and C 3 H 6 formation. This study offers a decisive description of Cr 2 O 3 modification for the CO 2 -assisted PDH process.