Comparative study on transition metal promoted Pt/SiO2 for oxidative dehydrogenation of propane with carbon dioxide

Transition metal is quantitatively investigated as a promoter of Pt-supported catalysts for the oxidative dehydrogenation of propane with CO₂ (CO₂-ODP). However, the criteria for selecting the transition metal are largely from trial and error. In this work, Pt/SiO₂ catalysts promoted with 3d transition metals (TMs) of Mn, Fe, Co or Ni (PtTM/SiO₂) are comparatively studied for CO₂-ODP. We found that the C₃H₆ selectivity and conversions of propane and CO₂ are clearly improved when TMs are introduced into Pt/SiO₂. Moreover, the apparent activation energy for the C₃H₆ formation during CO₂-ODP is decreased in the order of PtNi/SiO₂ > PtCo/SiO₂ > PtFe/SiO₂ > PtMn/SiO₂. Among the investigated catalysts, PtMn/SiO₂ is the most active and selective catalyst for the activation of C-H bonds in propane to produce C₃H₆ while PtNi/SiO₂ is the most favorable catalyst for the formation of by-products via the dry reforming of propane with CO₂ and propane cracking. Essentially, the catalytic results are well explained as the increased electron density of Pt over the PtTM/SiO₂ catalysts via the enhanced electron transfer from TM having a smaller electronegativity. This understanding is important for the rational design of a high-performance Pt-based bimetallic catalyst for CO₂-ODP.