Experimental evaluation of catalyst layers with bimodal pore structure for Fischer–Tropsch synthesis

Becker, Henning; Güttel, Robert; Turek, Thomas

doi:10.1016/j.cattod.2015.11.009

Cited by 13 publications

(10 citation statements)

References 45 publications

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“…Diffusivities of species in wax were estimated from Akgerman's correlation. 50,51 This correlation has been used previously, 6,21 and its predictions are similar to those obtained using correlations of Wang et al 5 and Makrodimitri et al 52 The effective diffusivity of the component was calculated from…”

Section: Model Descriptionmentioning

confidence: 53%

Effects of Catalyst Activity, Particle Size and Shape, and Process Conditions on Catalyst Effectiveness and Methane Selectivity for Fischer–Tropsch Reaction: A Modeling Study

Mandić

Todić

Živanić

et al. 2017

Ind. Eng. Chem. Res.

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We investigate effects of catalyst activity, catalyst particle shape (sphere, slab, and hollow cylinder), size (i.e., diffusion length), catalyst distribution (uniform vs eggshell type distribution for a spherical particle), and process conditions (temperature, pressure, syngas composition, and conversion level) on catalyst effectiveness factor and methane selectivity inside the catalyst pellet. In numerical simulations we utilize kinetic parameters for CO consumption rate and CH4 formation rate determined from experiments with a highly active Co/Re/γ-Al2O3 catalyst. It is found that the use of small spherical particles (0.2–0.5 mm) or eggshell distribution for larger spherical particles with catalyst layer thickness less than approximately 0.13 mm is needed to avoid negative impact of diffusional limitations on CH4 selectivity under typical Fischer–Tropsch synthesis operating conditions. For monolith reactors with wash-coated catalyst, diffusional limitations can be avoided by using a catalyst layer thickness less than 0.11 mm at base case conditions (473 K, 25 bar, and H2/CO molar ratio of 2).

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Section: Model Descriptionmentioning

confidence: 53%

Effects of Catalyst Activity, Particle Size and Shape, and Process Conditions on Catalyst Effectiveness and Methane Selectivity for Fischer–Tropsch Reaction: A Modeling Study

Mandić

Todić

Živanić

et al. 2017

Ind. Eng. Chem. Res.

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“…With the ASF-distribution alone a common behaviour of FT catalyst to exhibit an overly high methane selectivity, also observed in our previous experimental work, 22 cannot be predicted and a modification is required. A simple, yet rigorous modification comes by Förtsch et al, 51 which introduces only one further constant that describes the enhanced termination probability for methane.…”

Section: Kineticsmentioning

confidence: 66%

“…[24][25][26] By using transport pores the internal diffusion is enhanced and can improve the observed selectivities, as shown in the group of Montes 18,27 and also by our previous work. 22 Our existing simulation work 28 predicts the improved selectivity but also predicts an improved total productivity, which does not agree well with the experimental evidence. This can be a result of the simplified model, not taking axial convection into account.…”

Section: Introductionmentioning

confidence: 70%

“…The standard length of the reactor channel in this work is 50 mm and based on the size of our lab scale reactors. 22 For reactors of industrial scale this is likely to be substantially too short 64 and scenarios with longer channel length have been computed as well. With greater channel length the total accumulation of liquid product in the liquid film is higher, so is the film thickness and eventually its negative effect on productivity.…”

Section: View Article Onlinementioning

confidence: 99%

“…19 Microchannels with a wall-coated catalyst do not suffer from these heat distribution problems and have been tested experimentally. 17,[20][21][22][23] For both types of microreactors, packed beds and wall coatings, the variation of catalyst thickness has shown lower selectivities of desired long chain products when the catalyst layer thickness is increased. Using a maximal layer thickness is of paramount interest to operate commercial reactors with as few channels as possible for a given reactor size.…”

Section: Introductionmentioning

confidence: 99%

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Performance of diffusion-optimised Fischer–Tropsch catalyst layers in microchannel reactors at integral operation

Becker

Güttel²,

Turek

2019

Catal. Sci. Technol.

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Microchannel reactors offer a solution to utilize highly active catalysts for the Fischer-Tropsch process. The use of a wall-coated catalyst improves temperature control and prevents the negative correlation between pressure drop and catalyst efficiency. Diffusion limitations are, however, still a concern as a high reactor productivity demands a large catalyst layer thickness, to increase catalyst holdup while using as few channels as possible. Utilizing transport pores is one way of optimising the catalyst and achieving greater layer thicknesses while maintaining a good product selectivity. In this publication, we describe an isothermal and isobaric microchannel-reactor with a novel product film formation model and an improved selectivity description for accurate calculation of the product distribution. The optimisation of catalyst layers by defining ideal thicknesses and transport pore fraction is tested within realistic integral operation of the catalyst layers. Because the catalysts selectivity is strongly affected by the local syngas ratio the interplay of diffusion effects and convection in the gas phase is of major importance for the accurate prediction of catalyst behaviour. Non-optimised layers with great layer thickness and strong impact of diffusion limitations improve their performance with increasing conversion. Optimised layers with ideal amounts of transport pores and very thin layers, for which diffusion restrictions are less significant, on the other hand, exhibit an opposite behaviour and do not benefit from high conversions. These findings can also improve the interpretation of experimental results, which are often conducted at different conversion levels.

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Pore diffusion effects on catalyst effectiveness and selectivity of cobalt based Fischer-Tropsch catalyst

et al. 2020

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Experimental evaluation of catalyst layers with bimodal pore structure for Fischer–Tropsch synthesis

Cited by 13 publications

References 45 publications

Effects of Catalyst Activity, Particle Size and Shape, and Process Conditions on Catalyst Effectiveness and Methane Selectivity for Fischer–Tropsch Reaction: A Modeling Study

Effects of Catalyst Activity, Particle Size and Shape, and Process Conditions on Catalyst Effectiveness and Methane Selectivity for Fischer–Tropsch Reaction: A Modeling Study

Performance of diffusion-optimised Fischer–Tropsch catalyst layers in microchannel reactors at integral operation

Pore diffusion effects on catalyst effectiveness and selectivity of cobalt based Fischer-Tropsch catalyst

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