Modelling of monolithic converters with axial catalyst distribution

Psyllos, Apostolos; Philippopoulos, C.J.

doi:10.1016/0307-904x(93)90087-w

Cited by 14 publications

(17 citation statements)

References 9 publications

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“…After ignition in the monolith we require the entire monolith to be in the mass transfer controlled regime (with the ignited length of the monolith L ign is as large as possible) so that the exit concentration will reach the minimum possible value as seen in Eq. (18). As mentioned earlier, in the mass transfer controlled regime the reaction rates are much faster compared to the mass transfer rates from the fluid to the solid phase.…”

Section: Light-off With Nonuniform Catalyst Loadingmentioning

confidence: 93%

“…Oh and Cavendish [11] studied the effect of linearly increasing and decreasing activity profiles. Psyllos and Philippopoulos [18] observed that a parabolic activity distribution (decreasing from entrance to exit) reduces the warm-up time. Cominos and Gaviriilidis [19] found that an exponentially decreasing activity profile favors light-off near the inlet and also helps in alleviating the temperature gradients.…”

Section: Literature Reviewmentioning

confidence: 98%

“…(33) into Eq. (18). After the temperature front has completely propagated through the channel, the exit concentration is given by (assuming that the entire monolith is in the mass transfer controlled regime) Eq.…”

Section: Estimation Of Cumulative Emissionsmentioning

confidence: 99%

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Optimal design of catalytic converters for minimizing cold-start emissions

2004

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Section: Light-off With Nonuniform Catalyst Loadingmentioning

confidence: 93%

Section: Literature Reviewmentioning

confidence: 98%

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Optimal design of catalytic converters for minimizing cold-start emissions

2004

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“…It may be noted that there are many alternate but similar definitions of light-off in the literature [38][39][40][41][42][43] -one of the commonly used ones refers to light-off as the temperature condition required to achieve 50% conversion although we do not use this definition in the current work. Light-off in this work assumes or implies that a plot of the steady-state (bifurcation) diagram of solid temperature (or gas phase exit conversion or temperature) as a function of the inlet gas temperature exhibits a generalized S-shaped behavior in which the ignition or light-off point is represented by the normal limit point in the feasible region.…”

Section: Light-off Locationmentioning

confidence: 95%

Light‐off location and front diffusion in a catalytic monolith reactor

Ramanathan

Gopinath

2008

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).A one-dimensional solid-gas model has been used to study the light-off behavior in a reactor system. Techniques from nonlinear analysis are applied to first arrive at an analytical expression to estimate the light-off location in the reactor. The model is then extended to estimate the thickening of the light-off front in the vicinity of the light-off location due to heat diffusion effects in the solid substrate. Both these results are expressed in terms of all the important operating and design variables of the monolith reactor and also the reaction specific variables such as the kinetic parameters and heats of reaction. A specific case of a three-way catalyst (TWC) is numerically treated in detail to illustrate the application of this work. Finally, we focus on using the insight obtained from this study to suggest design guidelines to optimize the performance of automotive catalytic monolith reactors.

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“…In this case, the problem of optimizing the process in a reactor was formulated as the problem of arranging catalyst pellets with different distributions and concentrations of the active component along the catalyst bed length. For the first time, a mathematical model describing the effect of a nonuniform distribution of the active component along the monolith length in catalytic methane combustion was analyzed by Psyllos and Philippopoulos [7], who, however, did not attempt to find the optimal distribution. For a first-order heterogeneous reaction under isothermal conditions, it was shown that a uniform profile is optimal [8].…”

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confidence: 99%

Optimal Distribution of the Active Component in Catalytic Methane Oxidation

Khanaev

Borisova

Носков

2005

Theor Found Chem Eng

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Catalytic methane combustion is a highly efficient method for energy conversion at relatively low temperatures and methane concentrations, which simultaneously reduces NO x formation, cuts unburned hydrocarbon and CO emissions, and extends the ignition limits of fuel mixtures [1]. Catalytic methane combustion is used when the stable combustion of a methane-air mixture is impossible or a high degree of methane removal is necessary. From the standpoint of combustion conditions, there can be adiabatic and nonadiabatic catalytic combustion of methane-containing fuel mixtures.In the first method, lean fuel-air mixtures are fed at relatively high temperature to a catalytic monolith and burn under near-adiabatic conditions. This method is typically used in gas turbines [2] and can also be applied to clean gas emissions [3]. In the second method, simultaneously with catalytic combustion, the heat is removed (by convection, conduction, or radiation) from the reaction space, which decreases the catalyst temperature and improves the catalyst operating conditions. This method is mainly used in catalytic furnaces and chemical reactors.The most active components of a methane oxidation catalyst are platinum and/or palladium [1]. In the context of high prices of noble metals, of importance is the problem of saving these metals, which can be solved by creating the optimal distribution of the active component of the catalyst along the catalytic monolith length. Simultaneously, additional problems can be solved, e.g., the creation of a uniform temperature profile along the monolith length for improving the catalyst operating conditions [4] and also the facilitation of the ignition condition of the catalytic monolith [5]. The problem of increasing the efficiency of the catalytic process by creating the optimal distribution of the active component was previously considered for a single catalyst pellet. A theory was developed, a mathematical model was constructed, and the optimal distributions of the active component along the catalytic pellet radius were found for various boundary conditions on the pellet surface [6]. In this case, the problem of optimizing the process in a reactor was formulated as the problem of arranging catalyst pellets with different distributions and concentrations of the active component along the catalyst bed length. For the first time, a mathematical model describing the effect of a nonuniform distribution of the active component along the monolith length in catalytic methane combustion was analyzed by Psyllos and Philippopoulos [7], who, however, did not attempt to find the optimal distribution. For a first-order heterogeneous reaction under isothermal conditions, it was shown that a uniform profile is optimal [8]. In the general case, for an arbitrary kinetic equation, a method for determining the optimal distribution of the active component was presented in our previous work [9]. However, the optimal distributions of the active component under adiabatic conditions were not calculated before.The purpose of...

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Modelling of monolithic converters with axial catalyst distribution

Cited by 14 publications

References 9 publications

Optimal design of catalytic converters for minimizing cold-start emissions

Optimal design of catalytic converters for minimizing cold-start emissions

Light‐off location and front diffusion in a catalytic monolith reactor

Optimal Distribution of the Active Component in Catalytic Methane Oxidation

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