544595 Methane Pyrolysis on Complex Liquids: Reactive Separation of Hydrogen and Solid Carbon

Tuesday, June 4, 2019: 2:18 PM
Texas Ballroom D (Grand Hyatt San Antonio)
Eric McFarland1, Horia Metiu2, Michael Gordon1, Michael F. Doherty3, Clarke Palmer4, Jiren Zeng4, Dohyung Kang1 and Nazanin Rahimi1, (1)Department of Chemical Engineering, University of California, Santa Barbara, CA, (2)Department of Chemistry and Biochemistry, University of California - Santa Barbara, Santa Barbara, CA, (3)Chemical Engineering, University of California, Santa Barbara, CA, (4)University of California, Santa Barbara, CA

Steam methane reforming is the most economical means of producing H2 and CO2 at large scale; however, if, in the future, large segments of society are willing to pay a significant price for CO2 emissions reduction while natural gas remains relatively inexpensive, H2 produced from natural gas pyrolysis would offer the most cost competitive alternative. Specific compositions of molten metal alloys and/or complex molten salt mixtures at high temperature (~1000 C) are shown to have high activity for methane decomposition and high selectivity for molecular hydrogen and solid carbon as the only products. When the physical properties of the carbon and the liquids are selected optimally, solid carbon produced from pyrolysis in the high temperature melts can be conveniently separated in bubble column reactors. In molten alloys of Ni and Bi or mixtures of MnCl2 and KCl hydrogen and graphitic carbon products are produced at high conversion and high selectivity and are separable from the melt. Solid catalysts (including Ni/Al2O3) suspended in specific melts are also shown to be continuously reactivated as the high temperature liquid serves as a solvent to remove carbonaceous surface deposits prior to the irreversible formation of coke. Single pass methane conversion of over 98% to molecular H2 at over 98% selectivity is demonstrated in several molten metal alloys and molten salt mixtures. Fundamentals of C-H bond activation on melt surfaces will be discussed for metals and salts and distinctions made as to how the subsequent reaction pathways can produce different pyrolysis pathways and different types of solid carbons. The practical problem of producing a commercially acceptable carbon product will be discussed along with the heat transfer and materials of construction challenges.

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