Annette Trunschke and co-workers, Fritz Haber Institute of the Max Planck Society, Berlin, Germany, have investigated the adsorption of propane and propylene on multiwalled cabon nanotube (CNT) catalysts. By using calorimetry, the team was able to classify four types of adsorption site on the CNT surface:

A) Homogeneous high-energy sites that react reversibly with propane and irreversibly with propylene.
B) Heterogeneous, lower energy sites that react reversibly with propane and irreversibly with propylene.
C) Sites containing oxygenated species that interact weakly and reversibly with both propane and propylene.
D) Low-energy sites free of oxygen corresponding to the graphitic carbon base.

These interactions play a key role in the oxidative dehydrogenation of hydrocarbons — a process that has yet to be commercialized due to the higher reactivity of the products than the starting materials. Understanding the role of each type of site could aid the development of commercial catalysts.

• Calorimetric Study of Propane and Propylene Adsorption on the Active Surface of Multiwalled Carbon Nanotube Catalysts
  B. Frank, S. Wrabetz, O. V. Khavryuchenko, R. Blume, A. Trunschke, R. Schlögl,
  ChemPhysChem 2011.
  DOI: 10.1002/cphc.201100491