*3.2. Commercial-Scale Fixed-Bed Reactor Prototype Setup*

Figure 1 provides a schematic of the commercial-scale fixed-bed reactor, which was designed and assembled by OxEon Energy (formally known as Ceramatec) located in Salt Lake City, Utah, US. Approximately 6090 g of catalyst was loaded into a 4" (100 mm) nominal tube size, single tube reactor. The reactor has a 4.5" outer diameter (OD), 0.12" wall, and an inner diameter (ID) of 4.26". The catalyst occupies a length of approximately 49.5" of the reactor tube assembly. The center of the tube contains an internal cooling fin to disseminate the heat throughout the catalyst bed that is generated during exothermic reactions (Figure 2). The reactor and the skid that supports the reactor used in this test series are pictured in Figures 3 and 4 and provide the process flow diagram of the commercial-scale OxEon Energy test facility. Following the process flow diagram shown in Figure 4, a 3:1 ratio of H2/CO2

was flowed over the Fe:M2-3 catalyst at GHSV ranging between 8.0 <sup>×</sup> 10−<sup>4</sup> L/s-g and 1.4 <sup>×</sup> 10−<sup>3</sup> L/s-g. Nitrogen was used as the internal standard and all experiments were carried out at 300 ◦C and 20 bar.

The effluent fixed gases (H2, CO2, CO, N2) and CH4 from the reactor were analyzed in real time using an inline GC (Inficon) equipped with a TCD detector. Figure 4 shows that the system was designed such that when the products exit the reactor, they go to a hot trap and heavy hydrocarbons such as wax (typically seen if FT reactions using cobalt-based catalyst) are drained; the remainder of the hydrocarbons and non-converted synthesis gas goes to the fin tube to cool to room temperature. The gases then proceed through a chiller to a cold trap (cold trap is maintained at −4◦C) where the light oil and water are condensed, captured, and separated periodically. The non-condensate gases pass through a tee and are split such that part of the stream goes to flare and the other part goes to the recycle compressor. The composition of both gas streams are identical and the recycled feed is then blended back into the reactor at a ratio of 2:1 recycle feed to fresh feed (CO2 and H2). The flaring/removal of 1/3 of the gas stream is important to keep methane, an unwanted byproduct of this reaction, to reasonable levels. Labview is used for the inline GC analysis to ensure that the GHSV and CO2:H2 ratio remained constant during the recycling process. Analysis provided in Table 1 occurred approximately every 24 h for a given GHSV.

The long chain effluent from the reaction (i.e., hydrocarbons greater than C-2) was analyzed separately using a GC (Bruker 456, (Billerica, MA, USA) equipped with a flame ionization detector. It is important to note that all selectivities and yields are reported on a per carbon atom consumed basis and not per mole of product (i.e., propane selectivity is weighted by three due to the fact that it accounts for three carbon atoms per molecule). Five thermocouples (type and company) were positioned along the reactor bed and monitored by Labview to monitor the exothermic behavior of the reaction as it proceeds down the reactor bed.
