Revealing the mechanism of VOx/Ti3AlC2 for the dehydrogenation of propane

MAX phases exhibit a layer structure and unique characteristics that combine the high-temperature stability of ceramics and the good electrical properties of metals, attracting wide interest in catalysis. In this study, we prepared Ti3AlC2 MAX-supported V-based catalysts and investigated their catalytic performance in propane oxidative dehydrogenation and direct dehydrogenation reactions. The C3H8 conversion is approximately 8%, and the highest C3H6 selectivity exceeds 85% in oxidative dehydrogenation. Additionally, the initial conversion can reach 18% and the propene selectivity remains above 90% in propane catalytic dehydrogenation. Isolated VOx species exhibit the highest intrinsic activity and the strongest resistance to inactivation. Oxygen vacancies with low-valence V sites in vanadium oxides are considered to be the active sites. Combining kinetic experiments, it is found that the oxidative dehydrogenation of propane follows a Langmuir–Hinshelwood (L–H) mechanism rather than the traditional Mars–van Krevelen (MvK) mechanism. A reaction pathway is reasonably proposed in which O2 and C3H8 adsorb competitively and the reaction between adsorbed O2 and C3H8 is the rate-determining step.