Microkinetic modeling and analysis of ethanol partial oxidation and reforming reaction pathways on platinum at short contact times

Koehle, Maura; Mhadeshwar, Ashish B.

doi:10.1016/j.ces.2012.05.017

Cited by 19 publications

(15 citation statements)

References 91 publications

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“…Importantly, this first-principle analysis confirms the kinetic relevance of the H-abstraction steps that lead to acetaldehyde formation, postponing the C-C breaking stage, and the eventual re-equilibration of the fragments as precursors of CO, CO2, and methane ( Figure 9). A similarly comprehensive mechanism on platinum was developed by Koehle et al [69] for ethanol partial oxidation, where the total amount of reaction steps (50, each one considered in principle as reversible) was treated with a less aprioristic approach. The activation energy of every bond-break was estimated with a semi-empirical model, the so-called UBI-QEP, that relies on the interpolation of the calculated (or measured) binding energies of the intermediates with two parameters, catalyst coverage, and temperature, that are in turn eventually used to extrapolate the activation energies separating an intermediate from to the other.…”

Section: Calculated Energetic Profile Of Ethanol Degradationmentioning

confidence: 99%

Process Simulation for the Design and Scale Up of Heterogeneous Catalytic Process: Kinetic Modelling Issues

et al. 2017

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Abstract:Process simulation represents an important tool for plant design and optimization, either applied to well established or to newly developed processes. Suitable thermodynamic packages should be selected in order to properly describe the behavior of reactors and unit operations and to precisely define phase equilibria. Moreover, a detailed and representative kinetic scheme should be available to predict correctly the dependence of the process on its main variables. This review points out some models and methods for kinetic analysis specifically applied to the simulation of catalytic processes, as a basis for process design and optimization. Attention is paid also to microkinetic modelling and to the methods based on first principles, to elucidate mechanisms and independently calculate thermodynamic and kinetic parameters. Different case studies support the discussion. At first, we have selected two basic examples from the industrial chemistry practice, e.g., ammonia and methanol synthesis, which may be described through a relatively simple reaction pathway and the relative available kinetic scheme. Then, a more complex reaction network is deeply discussed to define the conversion of bioethanol into syngas/hydrogen or into building blocks, such as ethylene. In this case, lumped kinetic schemes completely fail the description of process behavior. Thus, in this case, more detailed-e.g., microkinetic-schemes should be available to implement into the simulator. However, the correct definition of all the kinetic data when complex microkinetic mechanisms are used, often leads to unreliable, highly correlated parameters. In such cases, greater effort to independently estimate some relevant kinetic/thermodynamic data through Density Functional Theory (DFT)/ab initio methods may be helpful to improve process description.

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Section: Calculated Energetic Profile Of Ethanol Degradationmentioning

confidence: 99%

Process Simulation for the Design and Scale Up of Heterogeneous Catalytic Process: Kinetic Modelling Issues

et al. 2017

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“…The terms of A, Γ, T, To, β, E, and R represent for the pre-exponential factor, site density (1.5×10 15 sites/cm 2 or 2.49×10 −9 mol/cm 2 [28,29]), absolute temperature, reference temperature (300 K), temperature exponent, activation energy, and universal gas constant (8.314 J/mol•K), respectively. The fraction of vacant sites, θv, is given by:…”

Section: Ch4 Dry Reforming Processmentioning

confidence: 99%

Combination of Langmuir-Hinshelwood-Hougen-Watson and microkinetic approaches for simulation of biogas dry reforming over a platinum-rhodium alumina catalyst

Sawatmongkhon

Theinnoi

Wongchang

et al. 2017

International Journal of Hydrogen Energy

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Dry reforming of CH4 on a platinum-rhodium alumina catalyst is selected to numerically investigate biogas reforming process. Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate expressions for dry reforming and reverse water-gas shift reactions are presented. Activation energies are estimated by combining microkinetics with the theory of unity bond indexquadratic exponential potential (UBI-QEP). Pre-exponential factors are initially obtained by using the transition state theory (TST) and optimised, later, by minimising errors between modelling and experimental data. Adsorption of CH4 on the catalyst surface is found to be the rate determining step in the range of relatively low temperature (600-770 °C), while at relatively high temperature (770-950 °C) the thermal cracking of adsorbed CH4 is the rate controlling step. Small effect of reverse water-gas shift reaction results in the ratio of H2 to CO produced less than unity for all operating conditions. The simulation shows that the dry reforming process proceeds with reaction rate far from equilibrium state. The presented mechanism is capable of predicting the dependence of biogas dry reforming activities (e.g., reactant conversions, product formations, H2 to CO ratio, and temperature profile inside the catalyst) on operating conditions (e.g., inlet temperature, heat supplied through the catalyst wall, and composition of biogas at inlet).

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“…It is evident that theoretical studies have focused on the decomposition pathways of ethanol, while all previously reported microkinetic models on ethanol conversion towards syngas are over noble metals, namely Pt [19,26] and Rh [27]. It is recognised though that the high cost of the latter poses significant economic difficulties to the commercial implementation of the process.…”

Section: Introductionmentioning

confidence: 99%

Microkinetic modelling and reaction pathway analysis of the steam reforming of ethanol over Ni/SiO2

Afolabi

Kechagiopoulos

2019

International Journal of Hydrogen Energy

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Hydrogen production via the steam reforming of biomass-derived ethanol is a promising environmental alternative to the use of fossil fuels and a means of clean power generation. A microkinetic modelling study of ethanol steam reforming (ESR) on Nickel is presented for the first time and validated with minimal parameter fitting against experimental data collected over a Ni/SiO2 catalyst. The thermodynamically consistent model utilises Transition State Theory and the UBI-QEP method for the determination of kinetic parameters and is able to describe correctly experimental trends across a wide range of conditions. The kinetically controlling reaction steps are predicted to occur in the dehydrogenation pathway of ethanol, with the latter found to proceed primarily via the formation of 1-hydroxyethyl. CC bond cleavage is predicted to take place at the ketene intermediate leading to the formation of CH2 and CO surface species. The latter intermediates proceed to react according to methane steam reforming and water gas shift pathways that are enhanced by the presence of water derived OH species. The experimentally observed negative reaction order for water is explained by the model predictions via surface saturation effects of adsorbed water species. The model results highlight a possible distinction between ethanol decomposition pathways as predicted by DFT calculations on Ni close-packed surfaces and ethanol steam reforming pathways at the broad range of experimental conditions considered.

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Microkinetic modeling and analysis of ethanol partial oxidation and reforming reaction pathways on platinum at short contact times

Cited by 19 publications

References 91 publications

Process Simulation for the Design and Scale Up of Heterogeneous Catalytic Process: Kinetic Modelling Issues

Process Simulation for the Design and Scale Up of Heterogeneous Catalytic Process: Kinetic Modelling Issues

Combination of Langmuir-Hinshelwood-Hougen-Watson and microkinetic approaches for simulation of biogas dry reforming over a platinum-rhodium alumina catalyst

Microkinetic modelling and reaction pathway analysis of the steam reforming of ethanol over Ni/SiO2

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