Revealing nature of active site and reaction mechanism of supported chromium oxide catalyst in propane direct dehydrogenation

Advanced metal oxide catalysts for propane dehydrogenation: from design strategy to dehydrogenation performance

Propane dehydrogenation (PDH) technology has been considered an important breakthrough to cope with the ever-increasing demand for propylene. Developing high-performance non-noble metal catalysts has emerged as an effective approach for replacing the currently used commercial Pt- and Cr-based catalysts with high cost and toxicity. Metal oxides have attracted much attention as PDH catalysts due to their high C-H activity, abundant active sites, and desirable dehydrogenation pathways. Regulating the supports and active sites through the rational design of structure and composition provides a new promising platform to improve the dehydrogenation activity and stability of metal oxide catalysts. This review systematically summarizes the catalytic mechanism of PDH. The rational design of metal oxide catalysts with suitable supports and precisely modulated active sites is described with their catalytic performances. In addition, the important roles played by reaction conditions to promote PDH processes are discussed. Furthermore, combined with well-developed advanced characterization methods, the in-depth exploration of the metal oxide-based PDH catalysts is highlighted. Finally, some perspectives for metal oxide-based PDH catalysts are concisely proposed to achieve their future innovations and industrialization.

A critical evaluation of the catalytic role of CO2 in propane dehydrogenation catalyzed by chromium oxide from a DFT-based microkinetic simulation

Propane dehydrogenation under CO₂ is an important catalytic route to obtain propene with a good balance between selectivity and stability. However, a precise description of the catalytic role of CO₂ in propane dehydrogenation is still absent. In this work, we focus on the elucidation of the role of CO₂ by using DFT-based microkinetic simulation. The influence of CO₂ is categorized as direct and indirect effects. It was found that the chemisorbed CO₂ can directly abstract hydrogen from propane and propyl with a comparable barrier to the counterpart at the surface oxygen site. On the other hand, the dissociation of CO₂ yields active surface species of CO* and O* which are actively involved in the removal of surface hydroxyls. It is found that the TOFs of both propane conversion and propene formation are significantly increased with the presence of CO₂, which is explained by the reduced apparent activation energy. The primary hydrogen abstraction is identified to be the most influential step from the DRC analysis. The main effects of CO₂ are concluded to be removing hydrogen and restoring oxygen vacancies from reaction pathway analysis.