Mixed-Oxide Redox Catalysts for Shale Gas Valorization Under Cyclic Redox Schemes

The significant increase in shale gas production has generated substantial economic incentive to convert light alkanes, e.g. methane and ethane, to value-added products. This is especially the case in distributed locations where methane and ethane are often subjected to flaring or rejection due to production fluctuations and limitations in transportation capacities. Although there are well-established commercial processes for methane and ethane conversion, they tend to be energy intensive with significant carbon dioxide emissions. The large energy consumptions for these processes are often resulted from the high endothermicity of methane/ethane conversion reactions, the complexity in product separations, and/or the energy consumptions for cryogenic air separation. The complexity of these conventional processes also limit their applications to convert distributed shale gas resources.

In this presentation, we discuss the chemical looping schemes as potentially attractive approaches for shale gas valorization, particularly in distributed, modular applications. 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 methane or ethane into value added products such as syngas (via methane partial oxidation) or ethylene (via ethane oxidative dehydrogenation); the oxygen depleted redox catalyst is then regenerated by reacting with a gaseous oxidant, e.g. air, steam, or CO₂. A few examples of utilizing the chemical looping concept for methane partial oxidation, CO₂ splitting, ethane oxidative dehydrogenation, and light alkane liquefaction are provided. Strategies to effectively design and optimize redox catalysts are also discussed.