Reaction Route Graphs. III. Non-Minimal Kinetic Mechanisms

Fishtik, Ilie; Callaghan, Caitlin; Datta, Ravindra

doi:10.1021/jp046115x

Cited by 29 publications

(28 citation statements)

References 20 publications

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“…36 This may be accomplished by appropriately combining the elementary steps into the so-called intermediate reactions (IR). [41][42][43] There are different ways in which the Campbell's DRC, once hence numerically computed for all the steps in a microkinetic model, may be utilized for identification of key steps and model reduction. 46 One such method is the so-called principal component analysis, 40,47,48 in which the eigenvalues and eigenvectors of the matrix X T X are computed.…”

Section: Parametric Sensitivity Analysismentioning

confidence: 99%

“…53 In other words, one needs both thermodynamic (affinity, or reversibility) and kinetic (resistance) characteristics of a reaction step to judge its significance in the overall scheme of things. The electrical network analogy based on the RR graph approach [41][42][43] incorporates both of these aspects. It, thus, comprehensively incorporates and illuminates the network structural constraints embodied by the two Kirchhoff's laws (mass balance, and Hess's law) described below, which further ascribe to reaction networks a complete and quantitative correspondence to electrical networks.…”

Section: Electrical Analogy and Reaction Networkmentioning

confidence: 99%

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Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.Campbell's degree of rate control

2015

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Elucidation of the key molecular steps and pathways in an overall reaction is of central importance in developing a better understanding of catalysis. Campbell's degree of rate control (DRC) is the leading methodology currently available for identifying the germane steps and key intermediates in a catalytic mechanism. We contrast Campbell's DRC to our alternate new approach involving an analysis and comparison of the "resistance" and de Donder "affinity," that is, the driving force, of the various steps and pathways in a mechanism, in a direct analogy to electrical networks. We show that our approach is as just rigorous and more insightful than Campbell's DRC. It clearly illuminates the bottleneck steps within a pathway and allows one to readily discriminate among competing pathways. The example used for a comparison of these two methodologies is a DFT study of the water-gas shift reaction on Pt-Re catalyst published recently.

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Section: Parametric Sensitivity Analysismentioning

confidence: 99%

Section: Electrical Analogy and Reaction Networkmentioning

confidence: 99%

Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.Campbell's degree of rate control

2015

Self Cite

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“…This can be done by investigating the effect of small variations in the parameters [39,56,62] or by graphical theoretical methods [63][64][65][66] [224] Surface diffusion phenomena can be incorporated into microkinetic models for supported particles [26,67,68]. Depending on the reaction conditions, some of the parameters may be much more important than others.…”

Section: Testmentioning

confidence: 99%

Theoretical Modelling of Catalytic Reactions

Stoltze

Nørskov

2008

Handbook of Heterogeneous Catalysis

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A catalyst is a substance which modifies the rate or the selectivity of a chemical reaction. A particular catalyst and reaction system is therefore characterized by the rates for different elementary steps in the reaction, and the theoretical modelling of catalytic reactions must therefore, as the end product, have the calculation of the kinetics.The kinetics of a catalytic reaction is usually measured in a reactor under conditions relevant to the industrial process. The measured overall rate can then be fitted to a mathematical model, the macroscopic kinetics. This is extremely convenient for process design purposes [1,2].If the aim is to explore the mechanism of the reaction and to understand which are the important parameters of the catalyst determining the activity, then a microkinetic model is needed. A microkinetic model is based on a detailed mechanism and independent information about the rates of the elementary steps involved and the stability of intermediates. It can be said that the microkinetic model is the synthesis of all the basic knowledge about a reaction over a given catalyst.The input into a microkinetic model is usually measured or calculated as the stability of intermediates, measured or calculated rates of elementary steps together with thermodynamic data for the gas (or liquid) phase above the catalyst.

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“…To overcome the before mentioned numerical issues, a new reduction technique for microkinetic reaction network models based on network-wide analysis of errors in the predicted reaction rates is proposed. Previous reduction techniques for chemical reaction networks are based on progressive species reduction with reparametrization [24], element flux analysis [25], integer linear programming [26], principle component analysis [27] and reaction route graphs [28][29][30].…”

Section: Introductionmentioning

confidence: 99%

“…The authors [28][29][30] established an analogy between reaction networks and electrical circuits. By considering reactions as chemical resistors, this information can be used to identify major barriers within the reaction network.…”

Section: Introductionmentioning

confidence: 99%

Reduction of microkinetic reaction models for reactor optimization exemplified for hydrogen production from methane

Karst

Maestri

Freund

et al. 2015

Chemical Engineering Journal

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h i g h l i g h t sWe present a new reduction technique for complex chemical reaction networks. This easy-to-use method is universal and ensures conservation of mass. We exemplify the reduction technique for a C1 microkinetic reaction network.The significantly reduced reaction network shows still an excellent agreement. a b s t r a c t Sustainable and efficient processes require optimal design and operating conditions. The determination of optimal process routes, however, is a challenging task. Either the models and underlying chemical reaction rate equations are not able to describe the process in a wide ranges of reaction conditions and thus limit the optimization space, or the models are too complex and numerically challenging to be used in dynamic optimization. To address this problem, in this contribution, a reduction technique for chemical reaction networks is proposed. It focuses on the sensitivity of the reaction kinetic model with respect to the removal of selected reaction steps and evaluates their significance for the prediction of the overall system behavior. The method is demonstrated for a C 1 microkinetic model describing methane conversion to syngas on Rh/Al 2 O 3 as catalyst. The original and the reduced microkinetic model show excellent qualitative and quantitative agreement. Subsequently, the reduced kinetic model is used for the optimization of a methane reformer to produce a hydrogen rich gas mixture as feed for polymer electrolyte membrane (PEM) fuel cell applications.

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Reaction Route Graphs. III. Non-Minimal Kinetic Mechanisms

Cited by 29 publications

References 20 publications

Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.Campbell's degree of rate control

Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.Campbell's degree of rate control

Theoretical Modelling of Catalytic Reactions

Reduction of microkinetic reaction models for reactor optimization exemplified for hydrogen production from methane

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