Thermal deactivation of heterogeneous catalyst, part 1. The theta‐rule ‐ a critical review

Kral, H.

doi:10.1002/ceat.270110116

Cited by 7 publications

(3 citation statements)

References 42 publications

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“…This comparison is made in Figure , which shows a linear correlation between log(−Δ S °) and log(−Δ H °) for several CO/adsorbent systems. A discussion of such a linear correlation, usually called the compensation effect, − is outside the scope of this paper. However, the values of the thermodynamic parameters derived here for the CO/Sr−Y system satisfactorily fit into the correlation, which lends further support to the present work.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic and Thermodynamic Characterization of Strontium Carbonyls Formed upon Carbon Monoxide Adsorption on the Zeolite Sr−Y

et al. 2003

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The adsorption of CO on the faujasite-type zeolite Sr-Y generates four types of carbonyls: the Sr(CO) 2+ species, which has a characteristic IR absorption band at 2191 cm -1 ; the Sr(OC) 2+ species at 2095 cm -1 ; Sr(CO) 2 2+ , which has a single mode at 2187 cm -1 ; and Sr(CO, OC) 2+ , which has a mode at 2098 cm -1 . The use of a variable-temperature IR cell allowing the simultaneous measurements of temperature, pressure, and coverages (intensities) of CO species to be made has allowed the determination of the standard enthalpy and entropy of formation of each species, so obtaining a fairly thorough thermodynamic characterization of the CO/Sr-Y system. C-and O-bonded carbonyl species were found to be in a temperature-dependent isomerization equilibrium, which was also studied by means of variable-temperature IR spectroscopy.

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Section: Resultsmentioning

confidence: 99%

Spectroscopic and Thermodynamic Characterization of Strontium Carbonyls Formed upon Carbon Monoxide Adsorption on the Zeolite Sr−Y

et al. 2003

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“…For example, comparing 1.52 and 1.58 m solutions, the rate constant at 500 K only changes by 70% despite an 88 kJ/mol difference in E a . It raises the question of whether this phenomenon is related to the kinetic compensation effect (KCE), − which has been reported for various other energetic materials, such as RDX, HMX, and NTO . The key feature of the KCE is the linear relation between ln( A ) and E a : in which α and θ are linear coefficients.…”

Section: Resultsmentioning

confidence: 99%

“…It raises the question of whether this phenomenon is related to the kinetic compensation effect (KCE), − which has been reported for various other energetic materials, such as RDX, HMX, and NTO . The key feature of the KCE is the linear relation between ln( A ) and E a : in which α and θ are linear coefficients. Widely different Arrenhius parameters have been reported for HAN in various phases or concentrations, ,,,,, as summarized in Figure along with the predictions by this work.…”

Section: Resultsmentioning

confidence: 99%

Thermal Decomposition Mechanism of Aqueous Hydroxylammonium Nitrate (HAN): Molecular Simulation and Kinetic Modeling

Zhang

Thynell

2018

J. Phys. Chem. A

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A detailed mechanism has been developed for thermal decomposition of hydroxylammonium nitrate (HAN) solutions, based on quantum mechanical calculations using the SMD-ωB97X-D method. The mechanism describes multiple kinetic processes, including nitration and nitrosation of hydroxylamine, HNO dimerization, and HONO-regeneration pathways involving H-abstraction reactions. Rate constants of elementary reactions were estimated using transition state theory with consideration of species' diffusion effect. Kinetic modeling was performed to predict species' evolutions in 0.1 m HAN in the temperature range of 463-523 K, and results show reasonable agreement with the experimental data from flow reactor studies. For more concentrated solutions, strong autocatalytic behaviors were predicted with the late emergence of NO and HONO, whose regeneration was previously considered as the major autocatalytic pathway. Sensitivity analysis results suggest an acid-catalyzed nitration-nitrosation pathway, based on which the autocatalysis should be caused by the rise of solution acidity. A linear correlation can be observed in the previously reported apparent Arrhenius parameters, which may be reconciled via a kinetic compensation effect.

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Thermal deactivation of heterogeneous catalysts. Part 2: The compensation effect and the Catalytic Paradox

Kral

1988

Chem Eng & Technol

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The interpretation of the term "compensation" obscures a logical contradiction, the catalytic paradox, which is caused by inconsistent validity ranges of the Arrhenius parameters, the preexponential factor and the activation energy. For this reason, a theory which contains the Arrhenius parameters cannot be established for the entire system (whole temperature range) on the basis of classical logic. Only the subsystems can be consistent and complete. One subsystem is the range of the topocatalytic concept which is relevant for thermal deactivation, thermal bistability and for all reactions with surface dependence of activity. The other is the range of the energetic concept which is preferred in fundamental research. In order to complete the subsystems, new consistent symbols are introduced. The change of particle size caused by thermal deactivation can result in four possible particle size effects, two of which have been discussed in the literature.

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Thermal deactivation of heterogeneous catalyst, part 1. The theta‐rule ‐ a critical review

Cited by 7 publications

References 42 publications

Spectroscopic and Thermodynamic Characterization of Strontium Carbonyls Formed upon Carbon Monoxide Adsorption on the Zeolite Sr−Y

Spectroscopic and Thermodynamic Characterization of Strontium Carbonyls Formed upon Carbon Monoxide Adsorption on the Zeolite Sr−Y

Thermal Decomposition Mechanism of Aqueous Hydroxylammonium Nitrate (HAN): Molecular Simulation and Kinetic Modeling

Thermal deactivation of heterogeneous catalysts. Part 2: The compensation effect and the Catalytic Paradox

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