(290b) Modular Ethane-to-Liquids Via Low-Temperature Chemical Looping Oxidative Dehydrogenation of Ethane

Authors: 
Neal, L., North Carolina State University
Haribal, V. P., North Carolina State University
Li, F., North Carolina State University
North American shale gas contains large amounts of natural gas liquids (NGLs). One NGL, ethane, poses particular transport challenges for producers. Unlike propane and butane, ethane is difficult to liquefy for transport, and ethane pipeline capacity is limited. This leads to frequent ethane “rejection” by reinjection into natural gas streams. Even rejection of ethane as fuel presents challenges due to interstate natural gas pipeline specifications. A modular scale process that can convert ethane into valuable and easily transportable products at geographically isolated gas processing facilities would capture significant value from this underutilized domestic resource. Ethylene production via steam cracking of ethane, which is the major industrial use of ethane, is not well suited to modular applications. The necessary high temperatures (>1000 °C), extensive heat exchange and recovery, and cryogenic separations demand large-scale operation to be economical.

Here we present a modular Ethane-To-Liquid fuel (m-ETL) system that is enabled by low-temperature (≤750 °C) redox catalysts for chemical looping-oxidative dehydrogenation (CL-ODH). In this approach, ethane is partially oxidized to ethylene and water by utilizing the lattice oxygen of a redox catalyst in a packed bed reactor. After the redox catalyst is depleted, the reactor is purged followed by the introduction of air to both regenerate the lattice oxygen and provide heat for the net reaction. By bundling multiple packed beds together in parallel, heat can be integrated between reaction steps. The ethylene-rich product stream is then compressed and oligomerized to light liquid olefins suitable for use as gasoline. Gaseous hydrocarbon byproducts, which are recycled to the reactor with a slip stream that is burned in an engine to provide power for the system. The ability to use number-up manufacturing for the CL-ODH bundles coupled with the modular scale of these bundles make them well-suited for low-cost distributed implementation. Process simulations based upon experimental redox catalysts highlight the potential productivity of a modular system. The economic potential of and challenges to successful implementation of the technology are also explored.

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