Fischer-Tropsch synthesis: Foregoing calcination and utilizing reduction promoters leads to improved conversion and selectivity with Co/silica

Journal Article · Sat Apr 14 00:00:00 EDT 2018 · Applied Catalysis. A, General

DOI:https://doi.org/10.1016/j.apcata.2018.04.013· OSTI ID:1461518

Martinelli, Michela ^[1]; Mehrbod, Mohammad ^[2]; Dawson, Chase ^[3]; Davis, Burtron H. ^[1]; Lietti, Luca ^[4]; Cronauer, Donald C. ^[5]; Kropf, A. Jeremy ^[5]; Marshall, Christopher L. ^[5]; Jacobs, Gary ^[6]

---

1. Center for Applied Energy Research, Lexington, KY (United States)
2. Dept. of Mechanical Engineering, San Antonio, TX (United States)
3. Center for Applied Energy Research, Lexington, KY (United States); Henry Clay High School, Lexington, KY (United States)
4. Politecnico di Milano, Milan (Italy)
5. Argonne National Lab. (ANL), Argonne, IL (United States)
6. Dept. of Mechanical Engineering, San Antonio, TX (United States); Dept. of Biomedical Engineering, San Antonio, TX (United States)

Foregoing calcination and utilizing direct reduction of cobalt nitrate led to the formation of smaller cobalt oxide nanoclusters in stronger interaction with silica support as intermediates of the activation process to Co° nanoparticles; this was demonstrated by TPR, TPR-MS, TPR-XANES, and TPR-EXAFS experiments using hydrogen. These intermediate cobalt oxides included a spinel (e.g., Co₃O₄) formed from oxidation of Co²⁺ species by NO₂, which in turn converted to CoO prior to formation of the metal. To improve the reducibility, metal promoters such as Pt, Re, Ru, and Ag were added. Hydrogen chemisorption and EXAFS experiments revealed smaller nanoparticles; Co-Co metal coordination numbers were significantly lower for the H₂-activated Co metal nanoparticles when direct reduction of the nitrate was used relative to H₂-activated air calcined catalysts. Comparing at the same space velocity, the best catalysts were Re and Pt promoted 12%Co/SiO₂ catalysts utilizing direct reduction of the nitrate, where initial conversions in a CSTR were up to 3.8 times higher and 71% higher than unpromoted and Pt promoted air calcined catalysts, respectively. At these conditions, methane production was lower (6.8 and 8.0% for Re and Pt promoted catalysts, respectively, by direct reduction versus 12.5 and 10.1% for unpromoted and Pt promoted air calcined catalysts) and C⁵⁺ selectivity was higher (81.2% and 81.5% for Re and Pt promoted catalysts, respectively, by direct reduction versus 73.4 and 78.8% for unpromoted and Pt promoted air calcined catalysts). In conclusion, the uncalcined catalysts were slightly less stable than the calcined samples, with the only exception being the rhenium promoted sample, where no visible deactivation was observed; this catalyst also had the highest catalytic activity on a per gram catalyst basis.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1461518
• Journal Information: Applied Catalysis. A, General, Vol. 559, Issue C; ISSN 0926-860X
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Fischer-Tropsch synthesis
Cobalt
Silica
Platinum
Co/SiO2
Promoters
Direct cobalt nitrate reduction
TPR-XANES
TPR-EXAFS