Fischer–Tropsch synthesis: Kinetics and water effect study over 25%Co/Al2O3 catalysts

Ma, Wanhong; Jacobs, Gary; Sparks, Dennis E.; Spicer, Robert L.; Davis, Burtron H.; Klettlinger, Jennifer L.S.; Yen, Chia H.

doi:10.1016/j.cattod.2013.10.014

Cited by 50 publications

(79 citation statements)

References 41 publications

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“…The influence of Ni metal on the deactivation rates of Co/Al 2 O 3 catalyst is carried out during 75 h in FTS at 230°C, 1 bar, and an H 2 :CO molar ratio of 2:1 with GHSV = 1500 h −1 . It is known that the deactivation of Co‐based catalysts during the FT reaction is unavoidable . The activity versus time‐on‐stream plot is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Modification of Co/Al₂ O₃ Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Nikparsa

Mirzaei

Rauch

2016

Int. J. Chem. Kinet.

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In this article, the effects of Ni (Co:Ni ratio = 4:1) on the performances and kinetic parameters of Co/Al2O3 nanocatalysts are explored in Fischer–Tropsch synthesis. As a result, the probability of chain growth increases and the deactivation rate decreases with addition of Ni. The properties of catalysts are characterized at different stages using Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and the vibrating sample magnetometer technique. The Co/Ni/Al2O3 catalyst with higher surface area and pore size exhibits higher activity and C5+ selectivity. The different results obtained for room‐temperature ferromagnetism have been attributed to the different metal oxides in the catalysts. The Fischer Tropsch kinetic study is done on the basis of the Langmuir–Hinshelwood–Hougen–Watson adsorption theory. Seven kinetic expressions based on the carbide and enolic mechanisms are selected. All experimental data are theoretically examined with these kinetic expressions to derive the best kinetic according to the linear and nonlinear approaches. The kinetic parameters of the fitted model, including the rate constant (k) and activation energy (Ea), are calculated with the Levenberg–Marquardt and genetic algorithm. The results show that by adding Ni the activation energy (Ea) decreases, the reaction rate (–RCO) increases, and the CO adsorption on the Co/Ni/Al2O3 catalyst is faster as well.

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Section: Resultsmentioning

confidence: 99%

Modification of Co/Al₂ O₃ Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Nikparsa

Mirzaei

Rauch

2016

Int. J. Chem. Kinet.

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“…7 and the chain growth probabilities of hydrocarbons and oxygenates after data fittings were listed in Table 6. Note that the C 1 compounds (methanol and methane) are plotted in the figure but are not included in the chain growth probability calculations since Rh based catalysts are not typical Fischer-Tropsch catalysts as Fe (Schulz, 2014) based catalysts or Co (Ma et al, 2014) based catalysts. The oxygenate distribution shows less C 1 (methanol) than would be expected by extrapolation of the ASF distribution for C 2 þ oxygenates, suggesting that methanol is not formed by the same route as ethanol and other higher oxygenates.…”

Section: Asf Analysismentioning

confidence: 99%

Kinetics study of C 2+ oxygenates synthesis from syngas over Rh–MnO x /SiO 2 catalysts

Mao

Zhang

et al. 2015

Chemical Engineering Science

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“…On the other hand, Co/silica catalysts having larger cobalt clusters exhibited a positive effect [53], and positive effects on cobalt catalysts have been suggested to be due to water increasing the concentration of surface active carbon species (e.g., unsupported Co and Co/titania [38]) or removing heavy wax from catalyst pores leading to a higher available site density (e.g., Co/silica with varying pore size [54]). Returning to cobalt/alumina catalysts, interestingly, by aging the catalyst sufficiently (i.e., the catalyst is significantly deactivated from its initial condition) [55] or utilizing catalysts with 10+ nm size [56], the deactivation rate becomes low, and the positive kinetic effect occurring on metallic cobalt particles can be observed. The main point is that the water effect can be modeled using a simple power law expression with a water effect parameter, m, and the magnitude and sign (i.e., positive [57] or negative [55,57]) of m provides valuable information about the structure of the catalyst.…”

Section: Modeling Of Site Suppression and Deactivationmentioning

confidence: 99%

“…Returning to cobalt/alumina catalysts, interestingly, by aging the catalyst sufficiently (i.e., the catalyst is significantly deactivated from its initial condition) [55] or utilizing catalysts with 10+ nm size [56], the deactivation rate becomes low, and the positive kinetic effect occurring on metallic cobalt particles can be observed. The main point is that the water effect can be modeled using a simple power law expression with a water effect parameter, m, and the magnitude and sign (i.e., positive [57] or negative [55,57]) of m provides valuable information about the structure of the catalyst.…”

Section: Modeling Of Site Suppression and Deactivationmentioning

confidence: 99%

Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

Jacobs¹,

Ma²,

Davis³

2014

Catalysts

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This focused review article underscores how metal reduction promoters can impact deactivation phenomena associated with cobalt Fischer-Tropsch synthesis catalysts. Promoters can exacerbate sintering if the additional cobalt metal clusters, formed as a result of the promoting effect, are in close proximity at the nanoscale to other cobalt particles on the surface. Recent efforts have shown that when promoters are used to facilitate the reduction of small crystallites with the aim of increasing surface Co 0 site densities (e.g., in research catalysts), ultra-small crystallites (e.g., <2-4.4 nm) formed are more susceptible to oxidation at high conversion relative to larger ones. The choice of promoter is important, as certain metals (e.g., Au) that promote cobalt oxide reduction can separate from cobalt during oxidation-reduction (regeneration) cycles. Finally, some elements have been identified to promote reduction but either poison the surface of Co 0 (e.g., Cu), or produce excessive light gas selectivity (e.g., Cu and Pd, or Au at high loading). Computational studies indicate that certain promoters may inhibit polymeric C formation by hindering C-C coupling.

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Fischer–Tropsch synthesis: Kinetics and water effect study over 25%Co/Al2O3 catalysts

Cited by 50 publications

References 41 publications

Modification of Co/Al₂ O₃ Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Modification of Co/Al₂ O₃ Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Kinetics study of C 2+ oxygenates synthesis from syngas over Rh–MnO x /SiO 2 catalysts

Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

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Fischer–Tropsch synthesis: Kinetics and water effect study over 25%Co/Al2O3 catalysts

Cited by 50 publications

References 41 publications

Modification of Co/Al2 O3 Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Modification of Co/Al2 O3 Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Kinetics study of C 2+ oxygenates synthesis from syngas over Rh–MnO x /SiO 2 catalysts

Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

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Modification of Co/Al₂ O₃ Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

Modification of Co/Al₂ O₃ Fischer-Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach