(736e) Chemical Looping CO2 splitting and Methane Reforming for Low-Carbon-Footprint Chemical Synthesis

Conversion of CO₂ to CO for chemical production is one of the most promising routs for widescale carbon utilization. However, traditional CO₂ to CO technologies pose challenges. Dry reforming of methane (DRM) which co-produces hydrogen is one of the most widely studied but has several drawbacks, including high energy demand, high temperatures (>800 °C), and coke formation. The 1:1 H₂:CO syngas product of dry reforming is useful for several chemicals, but few commercial processes can directly convert a 1:1 syngas without costly syngas separation, and/or water-gas shift (WGS). Due to the challenges of DRM, industrial syngas producers typically use methane partial-oxidation/autothermal reforming, followed by energy intensive separation to obtain high concentration CO feedstocks for synthesis (which offers no CO₂ utilization benefit). We present chemical looping catalyst for a hybrid redox process (HRP) that produces separate CO and syngas streams. The syngas is produced by partial oxidation of methane by the lattice oxygen of the HRP catalyst. In a subsequent step the lattice oxygen is regenerated by CO₂ splitting. Through choosing mixed metal oxides with catalytically active surfaces and/or modifying the particle surfaces with catalytically active metals, HRP offers high conversions in both reaction steps. Compared to dry reforming, HRP permits the efficient utilization of heat directly produces concentrated CO and 2:1 H­₂:CO streams without parasitic separations/WGS reactions.

We present experimental results that show over 95 % CO yield in the CO₂-splitting step and >95% selectivity towards syngas with a near 2:1 H2:CO in the partial oxidation step. The activity and selectivity of the redox catalysts during both the reduction and oxidation steps were tested. The performance of both platinum group metal (PGM)-containing and PGM-free redox catalyst are presented. PGM-free catalyst are shown to maintain excellent activity and stability in HRP operation, greatly enhancing the economic feasibility of the approach. Stable performance is observed over 500 cycles/125 hours with the phases intact. Simulations based on experimental HRP results are briefly presented indicating large cost and net CO₂ savingsfor production. HRP is an ideal choice for sustainable CO₂ fixation due to the wide industrial use for CO in chemical production.