Oscillations in pores of a catalyst particle in exothermic liquid (liquid–gas) reactions

Datsevich, Leonid

doi:10.1016/s0926-860x(03)00294-1

Cited by 19 publications

(34 citation statements)

References 11 publications

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“…One model, which describes the physical and mathematical basics of bubble evolution in porous catalyst particles, is the oscillation theory [8][9][10]. It considers multiphase reactions with gas or heat production where gas/vapor bubbles occur in catalyst pores due to a failure of mass or heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part I: Reactions with Gaseous Products

2010

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For heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on mass and heat transfer as well as on the effective reaction rate. This first of two contributions deals with the Ni-catalyzed decomposition of H 2 O 2 , which was used as a model system for an (almost) isothermal reaction with a gaseous product. (In part II the strongly exothermic hydrogenation of hexene will be analyzed, where gas/vapor bubbles may be generated by overheating of the catalyst.) The discharge of O 2 bubbles formed by decomposition of H 2 O 2 enhances the external mass and heat transfer up to one order of magnitude. This is in analogy to the well-known phenomena during nucleate boiling. The experiments and theoretical considerations also show that the internal mass transfer depends on the intensity of the reaction and thus on the H 2 O 2 concentration, which is in contradiction to the classical Thiele approach. This discrepancy could be explained by a modified model that takes the formation of bubbles into account.

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Section: Introductionmentioning

confidence: 99%

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part I: Reactions with Gaseous Products

2010

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“…The authors explain these phenomena with the complex interaction of inhibition, evaporation, and reaction. Coupled wetting and vaporization processes in exothermic, heterogeneously catalyzed reactions, which can significantly increase the rate, are also discussed in [12]. The effect of bubble formation within exothermic reactions was firstly theoretically considered by the oscillation theory [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part II: Exothermic Gas/Liquid Reactions

2010

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For heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on the effective reaction rate. This second of a series of two contributions deals with the Ni-catalyzed hydrogenation of hexene, which was used as a model system for an exothermic gas/liquid (G/L) reaction, where gas/vapor bubbles may be generated by overheating of the catalyst. (In part I, results of catalytic H 2 O 2 decomposition were presented, where the evolution of gas bubbles (O 2 ) always occurs.) A criterion for the formation of vapor bubbles for exothermic G/L reactions is presented, which was verified by experiments in a reactor with an inspection window. For a particle diameter of 6 mm, the effective kinetics of hexene hydrogenation is influenced by internal and external mass and heat transfer. A new and simple method to estimate the mass and heat transfer parameters and the effectiveness factors with regard to pore and external diffusion is presented, which combines the measured temperature difference(s) and the effective rate. For the given reaction conditions, the rate of hexene hydrogenation is not influenced by the evolution of vapor bubbles.

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“…The oscillatory behaviour in multiphase reactions on porous catalysts with heat and/or gas production has been considered in [1][2][3]. According to the given theoretical analysis, the oscillatory motion of liquid in a single catalyst pore caused by formation of gas-vapor bubbles can occur, if the number Da pore , which is equal to the ratio of the heat (or gas) generation in the pore to the maximum possible heat (or gas) removal by molecular conductivity (or diffusion) is more than unity.…”

Section: Introductionmentioning

confidence: 99%

“…According to the given theoretical analysis, the oscillatory motion of liquid in a single catalyst pore caused by formation of gas-vapor bubbles can occur, if the number Da pore , which is equal to the ratio of the heat (or gas) generation in the pore to the maximum possible heat (or gas) removal by molecular conductivity (or diffusion) is more than unity. In a real catalyst particle, as discussed in [1][2][3], the character of oscillations is very complex. The porous structure of the catalyst particle prepared, for instance, by compressing a fine powder, which itself has a fine pore structure, can be thought of as a network of macro-and micropores.…”

Section: Introductionmentioning

confidence: 99%

“…The catalyst particle can be characterized by zones where oscillations have different frequencies or even by stagnation zones where oscillations do not penetrate. As explained in [1,2], the roles of micro and macropores are different. Small pores serve as donors of heat, while as a result of less capillary pressure, large pores accept and utilize the generated heat, creating conditions for bubble formation inside (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Oscillation theory

Datsevich¹

2005

Applied Catalysis A: General

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Oscillations in pores of a catalyst particle in exothermic liquid (liquid–gas) reactions

Cited by 19 publications

References 11 publications

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part I: Reactions with Gaseous Products

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part I: Reactions with Gaseous Products

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part II: Exothermic Gas/Liquid Reactions

Oscillation theory

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