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

Oehmichen, Thomas; Datsevich, Leonid; Jess, Andreas

doi:10.1002/ceat.200900624

Cited by 13 publications

(15 citation statements)

References 14 publications

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“…At this scale, the evolution of the concentration of dissolving materials in the bulk is practically impossible to relate to the chemical reaction kinetic. Indeed, it results from the complex coupled phenomena of the chemical reaction and mass transport, complicated by others elements such as the reactive surface area evolution during dissolution and bubbling at the surface of the solid [34][35][36][37][53][54][55][56].…”

Section: Mechanism Of the Attack Of The Solid By Nitric Acidmentioning

confidence: 99%

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

Marc¹,

Magnaldo²,

Godard³

et al. 2018

EPJ Nuclear Sci. Technol.

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Abstract. Dissolution is a milestone of the head-end of hydrometallurgical processes, as the stabilization rates of the chemical elements determine the process performance and hold-up. This study aims at better understanding the chemical and physico-chemical phenomena of uranium dioxide dissolution reactions in nitric acid media in the Purex process, which separates the reusable materials and the final wastes of the spent nuclear fuels. It has been documented that the attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites, which leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks leads to the solid cleavage. It is shown here that the dissolution of the detached fragments is much slower than the process of the complete cleavage of the solid, and occurs with no disturbing phenomena, like gas bubbling. This fact has motivated the measurement of dissolution kinetics using optical microscopy and image processing. By further discriminating between external resistance and chemical reaction, the "true" chemical kinetics of the reaction have been measured, and the highly autocatalytic nature of the reaction confirmed. Based on these results, the constants of the chemical reactions kinetic laws have also been evaluated.

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Section: Mechanism Of the Attack Of The Solid By Nitric Acidmentioning

confidence: 99%

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

Marc¹,

Magnaldo²,

Godard³

et al. 2018

EPJ Nuclear Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…More recently, due to new developments in experimental techniques (see e.g. Enríquez et al 2014) and new applications, such as energy generation by chemical reactions (Oehmichen, Datsevich & Jess 2010), the topic has been the object of renewed attention.…”

mentioning

confidence: 99%

Gas depletion through single gas bubble diffusive growth and its effect on subsequent bubbles

et al. 2017

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When a gas bubble grows by diffusion in a gas-liquid solution, it affects the distribution of gas in its surroundings. If the density of the solution is sensitive to the local amount of dissolved gas, there is the potential for the onset of natural convection, which will affect the bubble growth rate. The experimental study of the successive quasi-static growth of many bubbles from the same nucleation site described in this paper illustrates some consequences of this effect. The enhanced growth due to convection causes a local depletion of dissolved gas in the neighbourhood of each bubble beyond that due to pure diffusion. The quantitative data of sequential bubble growth provided in the paper show that the radius-versus-time curves of subsequent bubbles differ from each other due to this phenomenon. A simplified model accounting for the local depletion is able to collapse the experimental curves and to predict the progressively increasing bubble detachment times.

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“…The critical question is whether bubbles form inside or outside the catalyst particles and at this time this question remains unanswered. Theoretical work of Datsevich (2003a;2003b;2004;2005, Oehmichen et al, 2010 has shown that formation of gas bubbles can influence transfer inside particles dramatically, whereas we have recently demonstrated in a microfluidic device, mimicking pores in a catalyst support, that both retardation as well as enhancement of transport on the pore is possible (Espinosa et al, 2018). Very recently, a simulation using APR of glycerol as model reaction showed the effect of bubbles on the kinetics and transport phenomena in a 2D system (Ripken et al, 2019).…”

Section: Effect Of Mass Transfermentioning

confidence: 96%

Influence of the Catalyst Particle Size on the Aqueous Phase Reforming of n-Butanol Over Rh/ZrO2

2020

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Butanol is a by-product obtained from biomass that can be valorized through aqueous phase reforming. Rh/ZrO 2 catalysts were prepared and characterized, varying the size of the support particles. The results showed a relatively mild effect of internal mass transport on butanol conversion. However, the influence of internal transport limitations on the product distribution was much stronger, promoting consecutive reactions, i.e., dehydrogenation, hydrogenolysis, and reforming of propane and ethane. Hydrogen consuming reactions, i.e., hydrogenolysis, were more strongly enhanced than hydrogen producing reactions due to internal concentration gradients. Large support particles deactivated faster, attributed to high concentrations of butyraldehyde inside the catalyst particles, enhancing deposit formation via aldol condensation reactions. Consequently, also the local butyric acid concentration was high, decreasing the local pH, enhancing Rh leaching. The influence of internal transfer limitation on product distribution and stability is discussed based on a reaction scheme with three main stages, i.e., (1) formation of liquid intermediates via dehydrogenation, (2) formation of gas via decarbonylation/decarboxylation reactions, and (3) hydrocarbon hydrogenolysis/reforming/dehydrogenation.

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

Cited by 13 publications

References 14 publications

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

Gas depletion through single gas bubble diffusive growth and its effect on subsequent bubbles

Influence of the Catalyst Particle Size on the Aqueous Phase Reforming of n-Butanol Over Rh/ZrO2

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