Abstract
Low-cost iron-based CO2 hydrogenation catalysts have shown promise as a viable route to the production of value-added hydrocarbon building blocks. It is envisioned that these hydrocarbons will be used to augment industrial chemical processes and produce drop-in replacement operational fuel. To this end, the U.S. Naval Research Laboratory (NRL) has been designing, testing, modeling, and evaluating CO2 hydrogenation catalysts in a laboratory-scale fixed-bed environment. To transition from the laboratory to a commercial process, the catalyst viability and performance must be evaluated at scale. The performance of a Macrolite®-supported iron-based catalyst in a commercial-scale fixed-bed modular reactor prototype was evaluated under different reactor feed rates and product recycling conditions. CO2 conversion increased from 26% to as high as 69% by recycling a portion of the product stream and CO selectivity was greatly reduced from 45% to 9% in favor of hydrocarbon production. In addition, the catalyst was successfully regenerated for optimum performance. Catalyst characterization by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), along with modeling and kinetic analysis, highlighted the potential challenges and benefits associated with scaling-up catalyst materials and processes for industrial implementation.
Highlights
Operating in a littoral and marine environment provides the U.S Navy with unique access to a vast environmental resource of carbon
OxEon Energy developed the reactor used in this study (Figure 1) along with the cooling fin (Figure 2) after having several years of experience working with the hydrogenation of syngas (CO and H2 ) to hydrocarbons using cobalt- and iron-based catalysts [18]
OxEon Energy is able to use a larger tube size because of the thermal management structure shown in Figures 1 and 2 that distributes the heat throughout the catalyst bed produced by the exothermic FT reaction
Summary
Operating in a littoral and marine environment provides the U.S Navy with unique access to a vast environmental resource of carbon. The world’s oceans are the largest carbon reservoirs containing approximately 38,000 gigatons [1]. Carbon and hydrogen are the principal building blocks needed to synthesize hydrocarbons. It is envisioned that these hydrocarbons may one day be used to produce operational fuel. Synthesizing “drop-in” replacement fuel at or near the point of use, translates into “Freedom of Action for the Warfighter” and potential long-term cost savings and strategic advantages for the Department of Defense (DOD) [2,3,4]. If the energy required for the process is nuclear or renewable, the entire low carbon fuel process could be considered CO2 neutral [5,6,7]
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