Kinetically induced multiplicity of steady states in integral catalytic reactors

Nibbelke, RH Rob; Hoebink, Jhbj Jozef; Marin, Gbmm Guy

doi:10.1016/s0009-2509(98)00055-4

Cited by 15 publications

(13 citation statements)

References 40 publications

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“…Typical catalysts are platinum (Pt), palladium (Pd), or a combination of both (Pt/Pd, e.g., alloyed, multilayered). During lightoff/lightout experiments, hysteresis phenomena of NO, CO, and HC conversion have repeatedly been reported in literature and attributed to noble metal oxidation [1,2] or to surface coverage effects [3].…”

Section: Introductionmentioning

confidence: 74%

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Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Dubbe

Bühner

Eigenberger

et al. 2016

Emiss. Control Sci. Technol.

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The diesel oxidation catalyst (DOC) plays a key role in diesel exhaust treatment systems. Typical noble metals used as active components are platinum (Pt) and palladium (Pd). During lightoff/lightout experiments, the catalyst reactivity during heating is in some cases different from the reactivity during cooling in the same reaction mixture. These so called hysteresis phenomena have repeatedly been reported for CO, NO, and HC conversion and are mostly attributed to noble metal oxidation and/or surface coverage effects. Hauff et al. have developed a kinetic model that is able to account for the hysteresis effects observed in NO conversion on Pt-only catalysts due to noble metal oxidation. The model was only validated for a limited range of NO concentrations and temperatures. In this follow-up, further experiments on Pt-only as well as on Pd-only catalysts will be presented for additional feed compositions. General transferability of the Pt-only model to Pd-only catalysts for NO-only is demonstrated. By addition of CO and propene to the feed, additional hysteresis phenomena are observed and will be discussed. On Pd-only, results indicate that under lean exhaust conditions, the noble metal can only be slightly reduced by CO. Interestingly, with a mix of CO and NO no reactivation is observed whereas the combination of CO, NO, and propene again shows reducing tendency. Based on these informations, a possible modeling approach will be proposed.

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Section: Introductionmentioning

confidence: 74%

“…The well known regular CO hysteresis on Pt due to surface coverage effects [3] vanishes when both CO and NO are present in the feed (see Fig. 7, left).…”

Section: Platinum Catalystmentioning

confidence: 82%

Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Dubbe

Bühner

Eigenberger

et al. 2016

Emiss. Control Sci. Technol.

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“…Purely kinetic sources belong to mass transport at the active site induced by nonlinear kinetics (e.g., adsorption vs. reaction) (Nibbelke et al, 1998), concurrent reactions/reaction networks (Balakotaiah and Luss, 1983;Elnashaie and Elshishini, 1993;Nibbelke et al, 1998;Mohl et al, 2001), or catalyst deactivation (Gilles, 1977;Eigenberger, 1983). Isothermal sources arise from mass transport at catalyst (diffusion) (Morbidelli et al, 1986;Lee et al, 1987) or reactor scale (convection, dispersion).…”

Section: State-space Multiplicitymentioning

confidence: 99%

Novel Multiplicity and Stability Criteria for Non-Isothermal Fixed-Bed Reactors

Bremer

Sundmacher

2021

Front. Energy Res.

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With the increasing need to utilize carbon dioxide, fixed-bed reactors for catalytic hydrogenation will become a decisive element for modern chemicals and energy carrier production. In this context, the resilience and flexibility to changing operating conditions become major objectives for the design and operation of real industrial-scale reactors. Therefore steady-state multiplicity and stability are essential measures, but so far, their quantification is primarily accessible for ideal reactor concepts with zero or infinite back-mixing. Based on a continuous stirred tank reactor cascade modeling approach, this work derives novel criteria for stability, multiplicity, and uniqueness applicable to real reactors with finite back-mixing. Furthermore, the connection to other reactor features such as runaway and parametric sensitivity is demonstrated and exemplified for CO2 methanation under realistic conditions. The new criteria indicate that thermo-kinetic multiplicities induced by back-mixing remain relevant even for high Bodenstein numbers. In consequence, generally accepted back-mixing criteria (e.g., Mears’ criterion) appear insufficient for real non-isothermal reactors. The criteria derived in this work are applicable to any exothermic reaction and reactors at any scale. Ignoring uniqueness and multiplicity would disregard a broad operating range and thus a substantial potential for reactor resilience and flexibility.

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“…(4) and (5) refer to the liquid and vapor, respectively. The individual velocities of the liquid and vapor can be recovered from…”

Section: Governing Equationsmentioning

confidence: 99%

“…Fluid flow with phase change heat transfer in porous media occurs in many engineering applications such as the drying processes in the food [1] and paper industries [2], heat exchangers [3] and chemical catalytic reactors [4]. In many of these systems, two-phase flow with phase change in porous media is encountered.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional numerical simulation of fluid flow with phase change heat transfer in an asymmetrically heated porous channel

Leong

Jin

et al. 2010

International Journal of Thermal Sciences

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Kinetically induced multiplicity of steady states in integral catalytic reactors

Cited by 15 publications

References 40 publications

Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Novel Multiplicity and Stability Criteria for Non-Isothermal Fixed-Bed Reactors

Three-dimensional numerical simulation of fluid flow with phase change heat transfer in an asymmetrically heated porous channel

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