Highly Selective Oxidative Dehydrogenation of Ethane to Ethylene via Chemical Looping with Oxygen Uncoupling through Structural Engineering of the Oxygen Carrier

摘要

The oxidative dehydrogenation of ethane (ODH) to produce ethylene offers advantages compared to the industry standard steam cracking, but its industrial application is hindered by costly air separation units needed to supply oxygen. A chemical-looping-based oxidative dehydrogenation (CL-ODH) scheme is presented, in which oxygen carriers supply gaseous oxygen in situ, which then reacts with ethane in the presence of a catalyst at a comparatively low temperature (500 degrees C). A common challenge of chemical looping processes beyond combustion is to suppress the overoxidation of hydrocarbons to COx to enable high product yields. It is demonstrated that the overoxidation of ethane can be eliminated completely through structural engineering of the perovskite oxygen carrier involving alkali-metal-based carbonate coatings, while maintaining the materials' ability to generate oxygen. Through CL-ODH, higher ethylene selectivity (approximate to 91) and yields (approximate to 39) are achieved compared to the conventional ODH scheme without oxygen carrier and cofeeding air/ethane. O-18-labeling experiments demonstrate that the carbonate layer functions like a diffusion barrier for ethane while being permeable for oxygen. Both the CL-ODH scheme and the material design strategy can be extended to other catalytic oxidation or dehydrogenation reactions requiring oxygen at different temperatures, offering enormous potential to intensify such processes.