Transient effectiveness factors in the dynamic analysis of heterogeneous reactors with porous catalyst particles

Bidabehere, Claudia María; García, Juan Rafael; Sedrán, Ulises

doi:10.1016/j.ces.2015.06.041

Cited by 14 publications

(26 citation statements)

References 30 publications

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“…The diffusional limitations inside the catalyst washcoat can be estimated as follows [70,71]: (14) In the above equation, the term . s i,e f f indicates the effective rate of formation of species i on the surface of the catalyst, Φ indicates the Thiele modulus, δ indicates the thickness of the porous washcoat, and the term C i,interface indicates the concentration of species i at the gas-catalyst interface.…”

Section: Of 27mentioning

confidence: 99%

RETRACTED: Catalytic Combustion Characteristics of Methane-Air Mixtures in Small-Scale Systems at Elevated Temperatures

Chen

Gao

2018

Catalysts

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The catalytic combustion characteristics of methane-air mixtures in small-scale systems were investigated at elevated temperatures, with particular emphasis on identifying the main factors that affect formation and removal of combustion-generated pollutants. Computational fluid dynamics simulations were performed using detailed chemical kinetic mechanisms, and more insights were offered into the phenomena occurring in the temperature range where homogeneous and heterogeneous reaction pathways are both important. Reaction engineering analysis was performed to provide an in-depth understanding of how to achieve low emissions of pollutants. Spatial distributions of the major species involved were presented to gain insight into the interplay between the two competing pathways involved. The results indicated that the distribution of oxidized products depends critically on the feed composition, dimension, temperature, and pressure. Small-scale catalytic systems enable low emissions of pollutants even in a high temperature environment, along with high combustion efficiency. The interplay between the two competing pathways via radicals is strong, and the heterogeneous pathway can significantly inhibit the homogeneous pathway. The inhibiting effect also accounts for the low emissions of nitrogen oxides. Almost all of the nitrogen oxides emitted by small-scale catalytic systems are nitric oxide. Catalytic combustion technology can be used to reduce the formation of undesired products, especially pollutant nitrogen oxide gases far below what can be achieved without catalysts. Recommendations for the design of small-scale catalytic systems are provided.

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Section: Of 27mentioning

confidence: 99%

RETRACTED: Catalytic Combustion Characteristics of Methane-Air Mixtures in Small-Scale Systems at Elevated Temperatures

Chen

Gao

2018

Catalysts

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“…Transport into, out of, and through zeolite domains are important rate-limiting steps for a complete description of the FCC process. 19 In the present work, we are interested in the overall transport through FCC particles. As transport through zeolite domains is very slow, 43 we neglect its contribution to the overall percolation ( section 3.4 ) and transport.…”

Section: Resultsmentioning

confidence: 99%

“…Without 3D visualization techniques, transport modeling is based on continuum models 18 , 19 or statistical models. 18 , 20 The main challenge, however, remains in accurately characterizing the complex pore structure with a limited number of parameters.…”

Section: Introductionmentioning

confidence: 99%

“…11 Another method includes focused ion beam-scanning electron microscopy (FIB-SEM), which can resolve in steamed zeolite crystal mesopores down to ∼5 nm in diameter, 16 while transmission electron microscopy (TEM) resolves even mesopores down to ∼2 nm in, for example, thin slices of zeolite powders. 17 Without 3D visualization techniques, transport modeling is based on continuum models 18,19 or statistical models. 18,20 The main challenge, however, remains in accurately characterizing the complex pore structure with a limited number of parameters.…”

Section: Introductionmentioning

confidence: 99%

“…Without 3D visualization techniques, transport modeling is based on continuum models , or statistical models. , The main challenge, however, remains in accurately characterizing the complex pore structure with a limited number of parameters . Direct visualization of the pore space of a catalyst particle offers the opportunity for quantitative determination of the geometrical parameters, such as local pore distributions, the pore size distribution, tortuosity and constrictivity, , and general principles of percolation theory, e.g.…”

Section: Introductionmentioning

confidence: 99%

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FIB-SEM Tomography Probes the Mesoscale Pore Space of an Individual Catalytic Cracking Particle

2016

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The overall performance of a catalyst particle strongly depends on the ability of mass transport through its pore space. Characterizing the three-dimensional structure of the macro- and mesopore space of a catalyst particle and establishing a correlation with transport efficiency is an essential step toward designing highly effective catalyst particles. In this work, a generally applicable workflow is presented to characterize the transport efficiency of individual catalyst particles. The developed workflow involves a multiscale characterization approach making use of a focused ion beam-scanning electron microscope (FIB-SEM). SEM imaging is performed on cross sections of 10.000 μm2, visualizing a set of catalyst particles, while FIB-SEM tomography visualized the pore space of a large number of 8 μm3 cubes (subvolumes) of individual catalyst particles. Geometrical parameters (porosity, pore connectivity, and heterogeneity) of the material were used to generate large numbers of virtual 3D volumes resembling the sample’s pore space characteristics, while being suitable for computationally demanding transport simulations. The transport ability, defined as the ratio of unhindered flow over hindered flow, is then determined via transport simulations through the virtual volumes. The simulation results are used as input for an upscaling routine based on an analogy with electrical networks, taking into account the spatial heterogeneity of the pore space over greater length scales. This novel approach is demonstrated for two distinct types of industrially manufactured fluid catalytic cracking (FCC) particles with zeolite Y as the active cracking component. Differences in physicochemical and catalytic properties were found to relate to differences in heterogeneities in the spatial porosity distribution. In addition to the characterization of existing FCC particles, our method of correlating pore space with transport efficiency does also allow for an up-front evaluation of the transport efficiency of new designs of FCC catalyst particles.

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Computational modeling of batch stirred tank reactor based on spherical catalyst particles

2018

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Transient effectiveness factors in the dynamic analysis of heterogeneous reactors with porous catalyst particles

Cited by 14 publications

References 30 publications

RETRACTED: Catalytic Combustion Characteristics of Methane-Air Mixtures in Small-Scale Systems at Elevated Temperatures

RETRACTED: Catalytic Combustion Characteristics of Methane-Air Mixtures in Small-Scale Systems at Elevated Temperatures

FIB-SEM Tomography Probes the Mesoscale Pore Space of an Individual Catalytic Cracking Particle

Computational modeling of batch stirred tank reactor based on spherical catalyst particles

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