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

Bukur, Dragomir B.; Mandić, Miloš; Todić, Branislav; Nikačević, Nikola M.

doi:10.1016/j.cattod.2018.10.069

Cited by 12 publications

(11 citation statements)

References 52 publications

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“…Therefore, the syngas must solubilize in the liquid film first and further diffuse into the pores and reach the internal active sites, accompanying with FTS reaction. 5,[7][8][9]14,38,[42][43][44] The external diffusion limitations in the gas and liquid films were assumed to be negligible because of the high gas linear velocity employed in industrial reactors. 45 Since the mesopores formed by ammonia solution etching were mainly dispersed on the internal surface of the macropores and diffusion length in mesopores was relatively short, the internal diffusion limitations in such mesopores were not considered in the pellet modeling.…”

Section: Modelingmentioning

confidence: 99%

“…13 The other approach is to alter the geometry of pellets for reducing the pressure drop of catalyst bed and enhancing the transport process. The simulation studies 4,5,8,14 indicated that in comparison to spherical pellets, more complex shapes, that is, trilobes or hollow cylindrical pellets, exhibit excellent hydrodynamic, transport characteristics under industrial conditions, whereas, the low mechanical strength for hollow cylinder pellet would limit its industrial application. 5 The approaches mentioned above, either the nonuniform distribution of active components or the adjustment on the geometry of pellets, mainly focus on how to shorten the diffusion distance.…”

Section: Introductionmentioning

confidence: 99%

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Mass transfer advantage of hierarchical structured cobalt‐based catalyst pellet for Fischer–Tropsch synthesis

Niu

Li²,

Xia

et al. 2021

AIChE Journal

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The low effectiveness factor of catalyst pellet caused by high internal diffusion limitation is a common issue in fixed-bed reactor. Nevertheless, hierarchical structured catalyst provides a promising solution for the contradiction between reaction activity and diffusion efficiency in large catalyst pellets. Herein, we studied the effect of pore structure parameters of the meso-macroporous catalyst on Fischer-Tropsch synthesis performances through experiment and pellet scale reaction-diffusion simulation.The pellet simulation firstly elucidated the reason for the significant improvement on activity and product selectivity for the meso-macroporous catalyst observed in our experiment. Further optimization via pellet simulation indicated the critical influences of wax filling degree and that the perfect matching between reaction and mass transfer rates by increasing macropore size and adjusting porosity within pellet enables the C 5+ space-time yield to the maximum. This work could provide a theoretical guideline for the engineering design of the hierarchical structured catalyst pellet.

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Section: Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mass transfer advantage of hierarchical structured cobalt‐based catalyst pellet for Fischer–Tropsch synthesis

Niu

Li²,

Xia

et al. 2021

AIChE Journal

View full text Add to dashboard Cite

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“…The rate of CO disappearance is calculated using the Yates and Satterfield (YS) kinetic model, which has been commonly used in previous modeling studies [21,25,[53][54][55][56][57]:…”

Section: Kineticsmentioning

confidence: 99%

“…In this work, a hybrid kinetic model adopted by Stamenic et al [55] and Bukur et al [56] was used. In their works, they coupled the YS model, the Ma model and a detailed kinetic model based on the CO insertion mechanism.…”

Section: Of 22mentioning

confidence: 99%

Thermal Assessment of a Micro Fibrous Fischer Tropsch Fixed Bed Reactor Using Computational Fluid Dynamics

et al. 2020

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A two-dimensional (2D) Computational Fluid Dynamics (CFD) scale-up model of the Fischer Tropsch reactor was developed to thermally compare the Microfibrous-Entrapped-Cobalt-Catalyst (MFECC) and the conventional Packed Bed Reactor (PBR). The model implements an advanced predictive detailed kinetic model to study the effect of a thermal runaway on C5+ hydrocarbon product selectivity. Results demonstrate the superior capability of the MFECC bed in mitigating hotspot formation due to its ultra-high thermal conductivity. Furthermore, a process intensification study for radial scale-up of the reactor bed from 15 mm internal diameter (ID) to 102 mm ID demonstrated that large tube diameters in PBR lead to temperature runaway >200 K corresponding to >90% CO conversion at 100% methane selectivity, which is highly undesirable. While the MFECC bed hotspot temperature corresponded to <10 K at >30% CO conversion, attributing to significantly high thermal conductivity of the MFECC bed. Moreover, a noticeable improvement in C5+ hydrocarbon selectivity >70% was observed in the MFECC bed in contrast to a significantly low number for the PBR (<5%).

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“…The optimal position of the active phase layer in the particle is related to the desired product yield maximization [13]. Several approaches can be used to minimize transport limitations: egg-shell catalyst with a specific thickness of the active layer [14,15], wash-coated monoliths [16], solid foams, and micro-and millireactors. Mazdidi et al have demonstrated that, by using a tubular fixed bed reactor, it is convenient to use different catalyst distributions along the bed length, as the diffusion limitations strongly depend on the reactant conversion [17].…”

Section: Introductionmentioning

confidence: 99%

Intraparticle Modeling of Non-Uniform Active Phase Distribution Catalyst

et al. 2020

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To maximize the performances of heterogeneous catalytic reactors, it is necessary to consider many parameters. Catalytic particle morphology (dimension, shape, active phase distribution) is generally previously established and seldom considered in the optimization of the catalyst to be specific for a given process. In this work, the influence of active phase distribution within spherical catalytic particles (egg-shell, egg-yolk and egg-white), on the yield and selectivity of a product is shown for a consecutive reaction network; here, the intermediate component is the main product of interest. Intraparticle mass and energy balances under non-steady conditions were implemented. Sensitivity studies lead to the identification of the optimal conditions, thus maximizing the yield of the intermediate for each active phase distribution. It was demonstrated that the egg-shell catalyst can maximize the intermediate yield, with a lower active-phase usage.

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

Cited by 12 publications

References 52 publications

Mass transfer advantage of hierarchical structured cobalt‐based catalyst pellet for Fischer–Tropsch synthesis

Mass transfer advantage of hierarchical structured cobalt‐based catalyst pellet for Fischer–Tropsch synthesis

Thermal Assessment of a Micro Fibrous Fischer Tropsch Fixed Bed Reactor Using Computational Fluid Dynamics

Intraparticle Modeling of Non-Uniform Active Phase Distribution Catalyst

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