Synthesis and Characterization of Co/C and Fe/C Nanocatalysts for Fischer–Tropsch Synthesis: A Comparative Study Using a Fixed-Bed Reactor

Abstract

Production of Fischer–Tropsch catalysts is challenging because it involves controlling and optimizing multiple parameters in numerous technical steps. Here, we present C-supported nanometric Fe and Co catalysts synthesized by plasma spraying, a method that contracts catalyst production into a single step, in contrast to traditional multistep catalyst production by precipitation or impregnation. The catalysts were reduced in situ and then tested for Fischer–Tropsch synthesis in a gas–solid fixed-bed reactor at 230 °C and 30-bar pressure for 24 h. The performance of plasma-synthesized catalysts was superior at a gas hourly space velocity of 6,000 mL·g cat –1·h–1, with Fe/C catalysts showing about 30% CO conversion per pass while Co/C catalysts yielded about 20% CO conversion. Identical C-supported Co and Fe catalysts prepared by impregnation or precipitation gave CO conversions of about 7% under similar reaction conditions.

Effect of CO Concentration on the α-Value of Plasma-Synthesized Co/C Catalyst in Fischer-Tropsch Synthesis

“…The Co species in the catalysts seemed to have become 'more metallic' in the sense of its electron-donating capability and hence the edge shift to the lower energies of the spectrum [41]. This was perhaps due to the simultaneous presence of metallic and carbidic species in the Co/C catalyst samples, as discussed in an earlier article [9]. The carbidic species in the samples were only evidenced by the XRD data analysis through RQA modeling using the High Score Plus software [7].…”

“…This study intended to investigate the possible outcomes of exposing our recently formulated plasma-synthesized Co/C catalyst [9], to a CO-rich FTS feedstock because the composition of syngas feedstock was observed to impact on the FTS product distribution [46]. In this work, application of CO-rich gas feed simulating bio-syngas has established the practicality of producing higher molecular-weight hydrocarbons in FTS, although with lower CO conversions when compared to the H 2 -rich feeds.…”

“…The Co/C catalyst under review has already been fully characterized: initially by XANES (Canadian Light Source (CLS) Synchrotron, Saskatoon, SK, Canada), and for porosity and BET specific surface area using the Accelerated Surface Area Porosimeter (ASAP) 2020 instrument (Micromeritics, Norcross, GA, USA) [9], and later the quantitative elemental analysis for the Co metal in the C support was performed by the carbon ignition method using a TG-DTA Setsys 2400 instrument (Setarum, Hillsborough, NJ, USA), while phase analysis was conducted on a Philips X'pert PRO X-ray Diffractometer (PANalytical, EA Almelo, The Netherlands), which is fitted with Ni-filters for the Cu Kα radiation of wavelength alpha1 = 1.5406 Å, produced at 40 kV and 50 mA (PANalytical, EA Almelo, The Netherlands). Curve-fitting modeling to determine the various amounts of each species in the catalyst was done using the PANalytical's High Score Plus software by Rietveld Quantitative Analysis (RQA).…”

“…In LT-FTS, a comparative study of identical single-metal Co/C catalysts produced by various methods showed that induction suspension plasma-spray (SPS) technology produces superior FTS catalysts [9].…”

Low‐temperature Fischer‐Tropsch synthesis using plasma‐synthesized nanometric Co/C and Fe/C catalysts

“…For example, although numerous process variables are necessary to provide the versatility needed to fabricate complex catalysts, plasma is a single-step method that decreases the number of stages in catalyst preparation, an approach that significantly lowers excessive process variables and parameters. [2] Other proposed advantages include superior catalyst performance, [3] achieved from the highly distributed active species, enhanced catalyst lifetime, shortened preparation time, and overall lower energy requirements, especially in cold plasma applications. [4] The nature and operation of the active species in the FTS catalysts are of substantial interest, having been studied using many characterization methods such as X-ray techniques (EXAFS, XRD, XPS), microscopy (SEM, TEM), [5] temperature-programmed reduction or oxidation (TPR/TPO), and adsorption techniques, namely physisorption and chemisorption, [6] among others.…”