Pt0.02Sn0.003Mg0.06 on γ-alumina: a stable catalyst for oxidative dehydrogenation of ethane

The advantages of two-step oxidative dehydrogenation as an alternative method for manufacturing small alkenes are outlined. In a nutshell, the process is based on separating the gaseous oxygen and hydrocarbon feeds in time. In the first step, alkanes are dehydrogenated in the presence of a solid oxygen carrier (without gaseous oxygen). Subsequently, the carrier is reoxidised using a gaseous feed. This process requires a dehydrogenation catalyst that is selective and stable under severe redox cycling. In search for such a catalyst, we prepare and study various platinum/tin catalysts supported on alumina. The catalysts are doped with either magnesia or potassium oxide. The activity, selectivity, and stability of these catalysts in the dehydrogenation of ethane to ethylene are then investigated under severe redox cycling conditions (600 °C and 10% (v/v) oxygen in the regeneration step). Pt0.02Sn0.003Mg0.06 is found to be the most stable combination. The catalysts' dispersion and the metal-support interactions are studied using transmission electron microscopy (TEM) and temperature-programmed hydrogen desorption (TPD). The effects of the (earth)alkali promoter and the interaction between the metal catalyst and support are discussed.