Carbon dioxide and C₂–C₃ alkanes are well-known greenhouse gases generated by human activities. Therefore, it is highly desirable to develop chemical processes that can jointly use CO₂ and C₂–C₃ alkanes in chemical synthesis.

Vadim V. Guliants and colleagues, University of Cincinnati, OH, USA, have synthesized Na-promoted vanadia catalysts supported on silica and investigated their behavior in propane oxidative dehydrogenation (ODH) reactions using O₂ and CO₂.

Propane ODH by O₂ and CO₂ was performed over Na-free and Na-promoted supported VO_x/SiO₂ catalysts. Typically, O₂ is used in ODH. CO₂ has a lower catalytic activity, which means that more reactive olefins are less likely to undergo undesirable combustion in its presence. The researchers found, that promotion with Na⁺ significantly improved the dispersion of surface VO_x species on silica. However, it resulted in the formation of surface Na metavanadate species or another reduced V³⁺/V⁴⁺ phase, which lacks catalytic activity in propane ODH in the presence of CO₂.

Raman spectroscopic studies revealed a trend that with increasing vanadium content on silica, 2D vanadia structures are formed at first. Then, the formation of 3D vanadia crystalline structure is favorable. Thus, the maximum amount of 2D vanadia structure that shows high activity for CO₂ ODH of propane was obtained in a monolayer-coverage range. Considerable carbon deposition was observed in used catalysts after propane ODH by CO₂, the extent of which correlated with their catalytic activity.

• Carbon Dioxide as Feedstock in Selective Oxidation of Propane,
  Jungshik Kang, Andrew D. Czaja, Vadim V. Guliants,
  Eur. J. Inorg. Chem. 2017.
  https://doi.org/10.1002/ejic.201701049