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Becker, Frank; Buchholz, Sigurd; Mleczko, Lesław

doi:10.1002/1522-2640(200106)73:6<686::aid-cite6862222>3.3.co;2-o

Cited by 2 publications

(3 citation statements)

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“…This expression is as used in our previous works. 28,34 It contains the modification of the effective diffusivity to include diffusion in transport pores. This modification is valid for sufficiently small transport pores to ensure a homogeneous concentration profile.…”

Section: Diffusion and Reaction In Catalystmentioning

confidence: 99%

“…Despite an abundance of simulation work on the FT process, to the authors' knowledge, there is no work satisfyingly describing and comparing the behaviour of catalysts under integral operation for different diffusion lengths or for employment of transport pores. Simulation work with differential reactors was either only focusing on pore optimisation in general 29,30 or elaborating specifically on the relation between diffusion, selectivity and pore filling degree 28,[31][32][33][34] or FT kinetics. 35,36 When complete reactors were considered often fluidized catalyst systems have been used, [37][38][39] which are useful for kinetic studies but not directly applicable to fixed bed reactors.…”

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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Section: Diffusion and Reaction In Catalystmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…Using the approach of Vervloet et al 18 for description of the chain growth probability as a function of reactant concentration and temperature, we have already shown that it is possible to find an ideal layer thickness, where the yield with respect to the desired products reaches a maximum. 49 In the present paper, the optimization potential is analyzed in detail with respect to the effective diffusivities in the catalyst and the transport pore phase by adjusting the transport pore fraction. Furthermore, the relevance of temperature gradients and the maximum allowable transport pore diameter are evaluated.…”

Section: Introductionmentioning

confidence: 99%

Enhancing internal mass transport in Fischer–Tropsch catalyst layers utilizing transport pores

Becker

Güttel

Turek

2016

Catal. Sci. Technol.

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Internal mass transport limitations inside Fischer-Tropsch catalysts due to the slow diffusion of reactants in the liquid-filled pores may significantly alter the selectivity and achievable productivity. In this work, diffusive restrictions for planar catalyst layers were investigated by mathematical modeling and simulation. A one-dimensional model utilizing empirical kinetics, incorporating transport pores as an additional pathway for mass transport and taking into account heat production, allows for calculation of catalyst efficiency and productivity towards C 5+ products. As diffusional mass transport leads to strong concentration gradients that impair selectivity, an optimum layer thickness with maximum C 5+ productivity can be found. Additional transport pores enhance the mass transport but reduce the amount of active phase, which requires a trade-off by optimizing the fraction of transport pores and layer thickness. For reference conditions, the catalyst layer with an ideal amount of transport pores and ideal thickness exhibits a productivity that is about 47% higher than that for the best layer without transport pores. This improvement requires transport pores with diameters not larger than about 60 μm. While the improvement potential significantly depends on the effective diffusivities, the effect of heat generation was found to be negligible.

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Cited by 2 publications

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

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

Enhancing internal mass transport in Fischer–Tropsch catalyst layers utilizing transport pores

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