X-ray photoelectron spectroscopic study of the surface state during ethane oxidative dehydrogenation at millisecond contact times

The chemical nature of Pt/alpha-Al2O3 catalysts has been studied using X-ray photoelectron spectroscopy (XPS) during, catalyst preparation and after being exposed to different feed compositions during autothermal oxidative dehydrogenation of ethane. In addition, the axial variation in surface chemistry has been probed by studying the front and back sides of the catalyst. Significant surface changes were observed following the addition and removal of chlorine to the feed. Chlorine addition led to large carbon deposits throughout the catalyst, and a significant surface concentration of chlorine on the catalyst surface. Chlorine addition also changed the oxidation state of platinum, leading to more oxidized platinum at the front of the monolith and more reduced platinum at the back of the monolith. Subsequent removal of chlorine led to the disappearance of chlorine from the XPS spectrum and to the removal of a significant amount of carbon from the front and back of the catalytic monolith.