A kinetic model of steady state ethylene epoxidation over a supported silver catalyst

Petrov, L.; Eliyas, A.; Шопов, Д.

doi:10.1016/s0166-9834(00)80301-2

Cited by 33 publications

(17 citation statements)

References 21 publications

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“…Both Langmuir–Hinshelwood (L-H) and Eley–Rideal (E-R, also recently referred to as Langmuir–Rideal) reaction rate expressions, with different active species and rate-determining steps, have been proposed. Petrov et al proposed a single site Eley–Rideal mechanism for ethylene conversion to EO and CO 2 that gives identical expressions for selective epoxidation and combustion . More recently, it has generally been accepted that ethylene oxidation over Ag catalysts follows a single- or dual-site Langmuir–Hinshelwood mechanism with surface atomic oxygen as the active oxygen species for both selective epoxidation and total combustion. ,− In summary, ethylene oxidation reaction kinetic studies have not been able to distinguish between L-H or E-R (L-R) reaction mechanisms and the different types of oxygen species present on Ag during ethylene oxidation, reflecting the inability of just kinetic studies to establish the fundamental molecular events.…”

Section: Kineticsmentioning

confidence: 99%

“…Although several studies contained promoted Ag catalysts, ,,, rate expressions incorporating the effect of promoters have not been discussed or reported. In the future, comprehensive rate expressions should be developed to also account for the impact of the promoters on the kinetics of ethylene oxidation by Ag catalysts.…”

Section: Kineticsmentioning

confidence: 99%

“…107,114−116 In summary, ethylene oxidation reaction kinetic studies have not been able to distinguish between L-H or E-R (L-R) reaction mechanisms and the different types of oxygen species present on Ag during ethylene oxidation, reflecting the inability of just kinetic studies to establish the fundamental molecular events. Although several studies contained promoted Ag catalysts, 107,113,114,117 rate expressions incorporating the effect of promoters have not been discussed or reported. In the future, comprehensive rate expressions should be developed to also account for the impact of the promoters on the kinetics of ethylene oxidation by Ag catalysts.…”

Section: Cuo Xmentioning

confidence: 99%

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Overview of Selective Oxidation of Ethylene to Ethylene Oxide by Ag Catalysts

et al. 2019

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Ethylene oxidation by Ag catalysts has been extensively investigated over the past few decades, but many key fundamental issues about this important catalytic system are still unresolved. This overview of the selective oxidation of ethylene to ethylene oxide by Ag catalysts critically examines the experimental and theoretical literature of this complex catalytic system: (i) the surface chemistry of silver catalysts (single crystal, powder/foil, and supported Ag/α-Al2O3), (ii) the role of promoters, (iii) the reaction kinetics, (iv) the reaction mechanism, (v) density functional theory (DFT), and (vi) microkinetic modeling. Only in the past few years have the modern catalysis research tools of in situ/operando spectroscopy and DFT calculations been applied to begin establishing fundamental structure–activity/selectivity relationships. This overview of the ethylene oxidation reaction by Ag catalysts covers what is known and what issues still need to be determined to advance the rational design of this important catalytic system.

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Section: Kineticsmentioning

confidence: 99%

Section: Kineticsmentioning

confidence: 99%

Section: Cuo Xmentioning

confidence: 99%

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Overview of Selective Oxidation of Ethylene to Ethylene Oxide by Ag Catalysts

et al. 2019

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“…The main attempts were focused on improvement of the silver catalyst via an optimal choice of particle size, support, promoters, etc., and led to the nowadays commercially used promoted and supported silver catalysts possessing selectivities of up to 90%. , Further increase of these values requires in-depth understanding of the nature of the active species, ,− possible reaction pathways and intermediates, ,− the role of the support and promoters, ,− etc. The initial ideas about reaction mechanism were based mainly on experimental evidence (e.g., kinetic studies). − Since the 1990s, density functional theory (DFT) calculations have started to augment the experimental observations significantly, and thereby, new insights into ethylene epoxidation mechanism have emerged. − The inconsistencies between the experimental and computational findings stem mainly from the incomplete or insufficient knowledge of the dynamical state of the catalyst surface under oxidative ethylene epoxidation conditions.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Reactivity of CaAg under Ethylene Epoxidation Conditions

et al. 2018

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The chemical behavior of CaAg as catalyst for ethylene epoxidation was studied using a combination of experimental (X-ray powder diffraction, scanning electron microscopy, thermal analysis and infrared spectroscopy), and quantum chemical techniques as well as real-space chemical bonding analysis. Under oxidative ethylene epoxidation conditions, the CaAg (010) surface possesses an outstanding stability during long-term experiments. It is caused by the formation of an ordered, stable and dense CaO passivation layer with a small amount of embedded Ag atoms. On this way, the (010) surface constitutes a kinetic barrier for further incorporation of oxygen into the subsurface region and thereby prevents further oxidative decomposition of CaAg. The calculated adsorption energies of the reaction species show strong adsorption of the reaction products that may explain the observed low conversion of ethylene toward ethylene oxide using CaAg as catalyst.

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“…To some extent, this can be attributed to the disguising effect of one product over the others [15,37]. The main reason for the contradictory conclusions is thought to be the different promoters on the catalyst surface [20,[22][23][24]351; in addition, the different supports, the presence of modifiers and the partial pressures of the reactants may be important, e.g.…”

Section: Ethene Oxidementioning

confidence: 99%

Influence of reaction products on the selective oxidation of ethene

Schouten

Borman

Westerterp

1996

Chemical Engineering and Processing: Process Intensification

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The kinetics of the selective oxidation of ethene in air over an industrial silver on a-alumina catalyst were studied. Special attention was paid to the influence of the reaction products on the reaction rates of epoxidation and complete combustion. Kinetic data were obtained in two different types of internal recycle reactor and in a cooled tubular reactor, and were fitted separately to several reaction rate expressions based on different kinetic models. A Langmuir-Hinshelwood mechanism, in which adsorbed ethene reacts with adsorbed molecular oxygen, was chosen as the best kinetic model. The reaction products compete for adsorption on the active sites and reduce the rates of both reactions. Carbon dioxide enhances the selectivity towards ethene oxide, whereas water has almost no influence on the selectivity. The fitting of the three individual data sets obtained in the three reactors results in accurate, but different, reaction rate expressions, whereas the fitting of the three data sets simultaneously results in less accurate reaction rate expressions. The systematic deviations found may be explained, to some extent, by differences in the operating regimes in each reactor. The main reason for the deviations is probably the different catalyst activities in the three reactors caused by poisoning. The effect of the addition of products to the feed on the behaviour of the cooled tubular reactor can be described reasonably well by a mathematical model in which the kinetic equations obtained in the laboratory reactors are incorporated. The results of these simulations are sensitive to the kinetics used.

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A kinetic model of steady state ethylene epoxidation over a supported silver catalyst

Cited by 33 publications

References 21 publications

Overview of Selective Oxidation of Ethylene to Ethylene Oxide by Ag Catalysts

Overview of Selective Oxidation of Ethylene to Ethylene Oxide by Ag Catalysts

Anisotropic Reactivity of CaAg under Ethylene Epoxidation Conditions

Influence of reaction products on the selective oxidation of ethene

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