Authors Preface

Yablonskii, Grigorii; Bykov, V. N.; Gorban, Aleksandr; Elokhin, V. I.

doi:10.1016/s0069-8040(08)70164-x

Cited by 28 publications

(45 citation statements)

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“…Actually, the data which were regressed by Schuurman et al (1992a) and van den Tillaart et al (1994) have been obtained after a reductive start-up and, hence are limited to these high reaction rates. Modification of this model by considering one active site only for adsorption of ethanol and oxygen does reveal multiplicity as could be expected ( Yablonskii et al, 1991) but the calculated reaction rates are far away from the experimental data. In particular the low stable branch is very low compared with the experimental low branch.…”

Section: Model Constructionmentioning

confidence: 72%

“…The situation is not so dear in the region with three' steady-states. In order to be able to predict unambiguously to which of the two lower branches an oxidative start-up leads, the separatrices in the five dimensional state space for the catalyst surface would have to be determined (Yablonskii et al (1991)). An oxidative as well as a reductive start-up lead to a unique stable steady-state at the middle branch up to an ethanol feed concentration of 290 molto 3 i.e.…”

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confidence: 99%

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Kinetic modelling of multiple steady-states for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst

Jelemenský

Kuster

Marin

1996

Chemical Engineering Science

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-Multiple steady-states data were used for the construction of a kinetic model for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst. A model, incorporating reversible creation of oxygen adatoms on the catalyst surface from surface hydroxyl as well as reversible formation of subsurface oxygen from oxygen adatoms, couid describe quantitatively all the observations. It was essential that the reaction rate coefficients for the formation of atomic and subsurface oxygen strongly depend on the corresponding degrees of coverage introducing positive and negative feedback features. INTRODUCTIONThe selective catalytic oxidation of alcohols and carbohydrates with dioxygen has received considerable attention in the recent past ( Mallat and Balker, 1994). Supported noble metals are the favourite catalysts. The reaction can be performed selectively at relatively mild conditions i.e. in aqueous media at a pH around 7 and at temperatures around 300 K.The major bottleneck for the commercial application consists in so-called catalyst deactivation. Several causes have been put forward for the latter ( Schuurman et al., 1992b;Mallat and Baiker, 1994;Vleeming et al., 1994). There is evidence for well known deactivation mechanisms such as metal dissolution and/or sintering (Schuurman et al., 1992b) and coverage of active sites by side or intermediate products of the desired reaction ( Mallat and Baiker, 1994). A phenomenon more specific to the considered type of reactions has also been suggested. It is referred to as overoxidation of the metal surface. The term stems from the observation that the loss in activity occurs in parallel with an increase of the catalyst potential (Vleeming et al., 1994).Recently steady-state multiplicity of the selective oxidation rate of aqueous ethanol over a platinum on carbon catalyst has been reported (Jelemensky et al., 1995). Up to three stable steady-state rates could be established over a feed ethanol concentration range from 300 to 400 mol m 3 in a continuous flow stirred tank reactor. The upper steady-state was reached by a reductive start-up procedure while the two lower steady-states required an oxidative start-up. The existence of steady-state multiplicity is believed to be rather common for selective oxidations and hydrogenations by noble metals in the liquid phase.Bifurcation phenomena, such as multiple steady-states (R~zon and Schmitz,1987;Zhdanov and Kasemo, 1994), autonomous oscillations ( Gray and Scott, 1990) or chaos ( Scott, 1991) are well documented for heterogeneous catalytic reactions. In the absence of heat and/or mass transport limitations such phenomena have to be caused by purely chemical feedback features such as autocatalysis. The observations of Jelemensky et al. (1995) were free of transport limitations.The present paper concerns the development of an intrinsic kinetic model for the platinum catalyzed selective oxidation of ethanol which allows a quantitative description of the complete set of data reported by Jelemensky et al. (...

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Section: Model Constructionmentioning

confidence: 72%

mentioning

confidence: 99%

Kinetic modelling of multiple steady-states for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst

Jelemenský

Kuster

Marin

1996

Chemical Engineering Science

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“…The equations (27) are therefore a set of coupled linear equations that can be rewritten as P S = v, where P is a n×n band matrix, which only non-vanishing entries are…”

Section: A Results In 1dmentioning

confidence: 99%

“…Having solved (at least formally) the set of equations (27) giving the stationary magnetization at each site a j , the general one-dimensional stationary magnetization in the presence of n zealots simply reads:…”

Section: A Results In 1dmentioning

confidence: 99%

“…In fact, real substrates (in 1D and 2D) display generally some degrees of spatial heterogeneity which are attributed to imperfections, such as dislocations and defects [27] that modify locally the interactions on the substrate. In some previous works translationally-invariant disordered models for catalysis have been considered within mean-field like approaches, i.e.…”

Section: Monomer-monomer Catalytic Reaction On An Inhomogeneous Sumentioning

confidence: 99%

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Voting and catalytic processes with inhomogeneities

Mobilia

Georgiev

2005

Phys. Rev. E

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We consider the dynamics of the voter model and of the monomer-monomer catalytic process in the presence of many "competing" inhomogeneities and show, through exact calculations and numerical simulations, that their presence results in a nontrivial fluctuating steady state whose properties are studied and turn out to specifically depend on the dimensionality of the system, the strength of the inhomogeneities and their separating distances. In fact, in arbitrary dimensions, we obtain an exact (yet formal) expression of the order parameters (magnetization and concentration of adsorbed particles) in the presence of an arbitrary number n of inhomogeneities ("zealots" in the voter language) and formal similarities with suitable electrostatic systems are pointed out. In the nontrivial cases n = 1, 2, we explicitly compute the static and long-time properties of the order parameters and therefore capture the generic features of the systems. When n > 2, the problems are studied through numerical simulations. In one spatial dimension, we also compute the expressions of the stationary order parameters in the completely disordered case, where n is arbitrary large. Particular attention is paid to the spatial dependence of the stationary order parameters and formal connections with electrostatics.

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Decoding the Past

2018

Kinetics of Chemical Reactions

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Authors Preface

Cited by 28 publications

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Kinetic modelling of multiple steady-states for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst

Kinetic modelling of multiple steady-states for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst

Voting and catalytic processes with inhomogeneities

Decoding the Past

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