Carbon deposition on Co catalysts during Fischer–Tropsch synthesis: A computational and experimental study

Tan, Kong Fei; Xu, Jing; Chang, Jie; Borgna, Armando; Saeys, Mark

doi:10.1016/j.jcat.2010.06.008

Cited by 101 publications

(32 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…XPS quantification shows that about 88% of the carbon species after 4 h of CO exposure at 260 °C is sp 2 carbon. As hexagonal graphite, primarily consisting of sp 2 carbon, is commensurate with the hexagonal close-packed surface of cobalt terraces, 40,42 we conclude that the less reactive carbon is graphitic. The contribution of carbidic carbon (282.9 eV 40,43,44 ) after 4 h of CO exposure at 260 °C is below 1%.…”

Section: Resultsmentioning

confidence: 68%

“…42 It has also been reported that the hexagonal graphite structure is thermodynamically favorable on the close-packed surface. 40,42 Figure 1b clearly shows that the formation of graphitic carbon is facilitated by higher CO exposure temperature. 34,35 We therefore conclude that the graphitic carbon formed via CO exposure mainly covers the terrace sites that dominate the surface of the relatively large cobalt nanoparticles in Co/SiO 2 .…”

Section: Resultsmentioning

confidence: 94%

“…Accordingly, we can assign these carbon species to atomic carbon or amorphous carbon on the basis of the literature. 33,35,39,40 As the temperature at which these amorphous carbon species can be hydrogenated is in the FT reaction regime (200–240 °C), these carbon species are most likely involved in the FT reaction. Figure 1a shows that the amount of the less reactive carbon increases strongly during prolonged CO exposure.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Influence of Carbon Deposits on the Cobalt-Catalyzed Fischer–Tropsch Reaction: Evidence of a Two-Site Reaction Model

et al. 2018

View full text Add to dashboard Cite

One of the well-known observations in the Fischer–Tropsch (FT) reaction is that the CH4 selectivity for cobalt catalysts is always higher than the value expected on the basis of the Anderson–Schulz–Flory (ASF) distribution. Depositing graphitic carbon on a cobalt catalyst strongly suppresses this non-ASF CH4, while the formation of higher hydrocarbons is much less affected. Carbon was laid down on the cobalt catalyst via the Boudouard reaction. We provide evidence that the amorphous carbon does not influence the FT reaction, as it can be easily hydrogenated under reaction conditions. Graphitic carbon is rapidly formed and cannot be removed. This unreactive form of carbon is located on terrace sites and mainly decreases the CO conversion by limiting CH4 formation. Despite nearly unchanged higher hydrocarbon yield, the presence of graphitic carbon enhances the chain-growth probability and strongly suppresses olefin hydrogenation. We demonstrate that graphitic carbon will slowly deposit on the cobalt catalysts during CO hydrogenation, thereby influencing CO conversion and the FT product distribution in a way similar to that for predeposited graphitic carbon. We also demonstrate that the buildup of graphitic carbon by 13CO increases the rate of C–C coupling during the 12C3H6 hydrogenation reaction, whose products follow an ASF-type product distribution of the FT reaction. We explain these results by a two-site model on the basis of insights into structure sensitivity of the underlying reaction steps in the FT mechanism: carbon formed on step-edge sites is involved in chain growth or can migrate to terrace sites, where it is rapidly hydrogenated to CH4. The primary olefinic FT products are predominantly hydrogenated on terrace sites. Covering the terraces by graphitic carbon increases the residence time of CHx intermediates, in line with decreased CH4 selectivity and increased chain-growth rate.

show abstract

Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Influence of Carbon Deposits on the Cobalt-Catalyzed Fischer–Tropsch Reaction: Evidence of a Two-Site Reaction Model

et al. 2018

View full text Add to dashboard Cite

show abstract

“…There are several deactivation routes for cobalt FTS catalysts – sintering, 25–27 irreversible oxidation and formation of metal–support compounds, 28,29 carbon deposition 26,30,31 and poisoning. 32 The main bottlenecks in investigation of FTS catalysts are measurement of Co surface area via chemisorption (throughput of one sample per day per machine) and testing, which requires 60–100 h to provide a stable baseline and further tests of several months to estimate the long term stability of the catalyst.…”

Section: Introductionmentioning

confidence: 99%

Proxy-based accelerated discovery of Fischer–Tropsch catalysts

et al. 2015

View full text Add to dashboard Cite

show abstract

“…With respect to the important question of selectivity of the FT reaction, according to one school of thought, small particles are not reactive, as strongly adsorbed CO inhibits chain growth; [2,3] according to others, step-edge sites are required that are not stable on small particles. [4][5][6] This explains the observation that selectivity toward the produc-tion of methane strongly increases and the rate of CO consumption decreases for smaller transition-metal nanoparticles.…”

mentioning

confidence: 99%

The Optimally Performing Fischer–Tropsch Catalyst

2014

View full text Add to dashboard Cite

Microkinetics simulations are presented based on DFT‐determined elementary reaction steps of the Fischer–Tropsch (FT) reaction. The formation of long‐chain hydrocarbons occurs on stepped Ru surfaces with CH as the inserting monomer, whereas planar Ru only produces methane because of slow CO activation. By varying the metal–carbon and metal–oxygen interaction energy, three reactivity regimes are identified with rates being controlled by CO dissociation, chain‐growth termination, or water removal. Predicted surface coverages are dominated by CO, C, or O, respectively. Optimum FT performance occurs at the interphase of the regimes of limited CO dissociation and chain‐growth termination. Current FT catalysts are suboptimal, as they are limited by CO activation and/or O removal.

show abstract

Carbon deposition on Co catalysts during Fischer–Tropsch synthesis: A computational and experimental study

Cited by 101 publications

References 56 publications

Influence of Carbon Deposits on the Cobalt-Catalyzed Fischer–Tropsch Reaction: Evidence of a Two-Site Reaction Model

Influence of Carbon Deposits on the Cobalt-Catalyzed Fischer–Tropsch Reaction: Evidence of a Two-Site Reaction Model

Proxy-based accelerated discovery of Fischer–Tropsch catalysts

The Optimally Performing Fischer–Tropsch Catalyst

Contact Info

Product

Resources

About