Mixed Oxide Redox Catalysts for Chemical Looping Oxidative Dehydrogenation of Light Alkanes

The supplies of light alkanes, e.g. ethane and propane, have increased considerably over the recent years resulting from the shale gas revolution. Although there are well-established commercial processes for alkane conversions, they tend to be capital and energy intensive due to the endothermicity of cracking or dehydrogenation reactions, complexity in product separations, and/or energy consumptions for cryogenic air separation. The complexity of these conventional processes also limit their applications to convert distributed shale gas resources. Therefore, novel approaches that can intensify light alkane conversion processes while reducing the energy consumptions and carbon emissions are highly desirable.

This presentation discusses a chemical looping – oxidative dehydrogenation (CL-ODH) scheme which can simplify the conversion of light alkanes to olefins. The chemical looping process utilizes an oxygen carrier, also known as redox catalysts, to convert shale gas components via an indirect reduction-oxidation (redox) scheme: the redox catalyst first releases its lattice oxygen to convert, e.g. ethane into ethylene; the oxygen depleted redox catalyst is then regenerated with air while releasing heat. The CL-ODH allows intensified, auto-thermal operation without the needs for air separation. As such, over 80% reduction in CO₂ emission can be realized. In this presentation, the design principles for the redox catalysts and the underlying mechanisms for ethane CL-ODH are discussed. Results from second law analysis will also be presented to illustrate the benefits of CL-ODH relative to conventional approaches. Examples of CL-ODH for the conversions of C3+ alkanes will also be provided.