The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Olaf Deutschmann - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Methane and Propane Reforming Over a Porous Rh/Al$_{2}$O$_{3}$ Catalyst in Stagnation-Flows: Impact of Internal and External Mass Transfer Limitations on Species Profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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numerical simulation of methane and propane reforming over a porous rh al _ 2 o _ 3 catalyst in stagnation flows impact of Internal and external Mass Transfer limitations on species profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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real time simulation of dual layer catalytic converters based on the Internal Mass Transfer coefficient approach
Topics in Catalysis, 2017Co-Authors: J Rink, B Mozaffari, Steffen Tischer, Olaf Deutschmann, Martin VotsmeierAbstract:A new numerically efficient simulator for dual layer catalysts is implemented and its performance is demonstrated using the example of the dual layer ammonia oxidation catalyst. For the solution of the radial Mass balances, each washcoat layer is represented by a single volume element and the diffusive Mass fluxes into and within the washcoat are computed based on the concept of the Internal Mass Transfer coefficients. The performance of the new simulator is compared against a reference simulator that fully resolves the concentration profiles in the washcoat. For a steady state test case, the error introduced by the new solution scheme is below 2 % for all relevant exhaust components. For a transient test case, the deviations become more significant. For the simulation of a WHTC, the maximum deviation in the NH3 outlet concentration is 23.3 %, whereas the cumulated NH3 emissions deviate by 10.6 %.With the new simulator, the 1800 s of the transient WHTC cycle can be simulated within 53 s on a standard laptop, 30 times faster than real time.
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Mass Transfer Effects in Stagnation Flows on a Porous Catalyst: Water-Gas-Shift Reaction Over Rh/Al2O3
Zeitschrift für Physikalische Chemie, 2015Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract: Water-gas-shift(WGS)andreversewater-gas-shift(RWGS)reactionsarenumericallyinvestigatedinastagnation-flowonaporous Rh/Al 2 O 3 catalyst.Ex-ternalandInternalMassTransfereffectsarestudiedusingthreedifferentmodelsfortheMasstransportandchemicalconversioninsidetheporouscatalyst:thedusty-gasmodel,asetofreaction-diffusionequations,andtheeffectivenessfac-torapproach.Allthreemodelsarecoupledwiththeboundarylayerequationstodescribethepotentialflowonthestagnationdisc,andamulti-stepsurfacere-actionmechanismisimplemented.Thenumericallypredictedspeciesprofilesintheexternalboundarylayerarecomparedwithrecentlymeasuredprofiles.Inter-nalMassTransferlimitationsaremoresignificantthanexternalonesincaseofthe 100μm thickcatalystlayer.Theeffectsofcatalyststructure(thickness,meanporediameter,porosity,tortuosity)aswellasflowrateandpressureonchemicalconversionarediscussed. Keywords: Stagnation-Flow, External and Internal Mass Transfer, Water-Gas-ShiftReaction,ReverseWater-Gas-Shift,Rhodium,Dusty-GasModel,Reaction-Diffusion.
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Numerical modeling of stagnation-flows on porous catalytic surfaces: CO oxidation on Rh/Al2O3
Chemical Engineering Science, 2013Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract A stagnation-flow on a catalytic porous plate is modeled one-dimensionally coupled with multi-step surface reaction mechanisms and molecular transport (diffusion and conduction) in the flow field and the porous catalyst. Internal Mass transport inside the porous catalyst is studied with three different models: instantaneous diffusion (infinitely fast Mass transport), effectiveness factor, and one-dimensional reaction-diffusion equations. A new computer code, DETCHEM STAG , is presented to execute the numerical model. The oxidation of CO over a porous Rh/Al 2 O 3 surface is studied exemplarily. Experimental measurements are carried out to apply the developed model and the computer code. External and the Internal Mass Transfer effects in front of and inside the porous catalyst are discussed. Internal Mass Transfer limitations become important in case of a thick catalyst layer for accurately predicting the experimental results.
Hüseyin Karadeniz - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Methane and Propane Reforming Over a Porous Rh/Al$_{2}$O$_{3}$ Catalyst in Stagnation-Flows: Impact of Internal and External Mass Transfer Limitations on Species Profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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numerical simulation of methane and propane reforming over a porous rh al _ 2 o _ 3 catalyst in stagnation flows impact of Internal and external Mass Transfer limitations on species profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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Mass Transfer Effects in Stagnation Flows on a Porous Catalyst: Water-Gas-Shift Reaction Over Rh/Al2O3
Zeitschrift für Physikalische Chemie, 2015Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract: Water-gas-shift(WGS)andreversewater-gas-shift(RWGS)reactionsarenumericallyinvestigatedinastagnation-flowonaporous Rh/Al 2 O 3 catalyst.Ex-ternalandInternalMassTransfereffectsarestudiedusingthreedifferentmodelsfortheMasstransportandchemicalconversioninsidetheporouscatalyst:thedusty-gasmodel,asetofreaction-diffusionequations,andtheeffectivenessfac-torapproach.Allthreemodelsarecoupledwiththeboundarylayerequationstodescribethepotentialflowonthestagnationdisc,andamulti-stepsurfacere-actionmechanismisimplemented.Thenumericallypredictedspeciesprofilesintheexternalboundarylayerarecomparedwithrecentlymeasuredprofiles.Inter-nalMassTransferlimitationsaremoresignificantthanexternalonesincaseofthe 100μm thickcatalystlayer.Theeffectsofcatalyststructure(thickness,meanporediameter,porosity,tortuosity)aswellasflowrateandpressureonchemicalconversionarediscussed. Keywords: Stagnation-Flow, External and Internal Mass Transfer, Water-Gas-ShiftReaction,ReverseWater-Gas-Shift,Rhodium,Dusty-GasModel,Reaction-Diffusion.
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Numerical modeling of stagnation-flows on porous catalytic surfaces: CO oxidation on Rh/Al2O3
Chemical Engineering Science, 2013Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract A stagnation-flow on a catalytic porous plate is modeled one-dimensionally coupled with multi-step surface reaction mechanisms and molecular transport (diffusion and conduction) in the flow field and the porous catalyst. Internal Mass transport inside the porous catalyst is studied with three different models: instantaneous diffusion (infinitely fast Mass transport), effectiveness factor, and one-dimensional reaction-diffusion equations. A new computer code, DETCHEM STAG , is presented to execute the numerical model. The oxidation of CO over a porous Rh/Al 2 O 3 surface is studied exemplarily. Experimental measurements are carried out to apply the developed model and the computer code. External and the Internal Mass Transfer effects in front of and inside the porous catalyst are discussed. Internal Mass Transfer limitations become important in case of a thick catalyst layer for accurately predicting the experimental results.
Steffen Tischer - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Methane and Propane Reforming Over a Porous Rh/Al$_{2}$O$_{3}$ Catalyst in Stagnation-Flows: Impact of Internal and External Mass Transfer Limitations on Species Profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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numerical simulation of methane and propane reforming over a porous rh al _ 2 o _ 3 catalyst in stagnation flows impact of Internal and external Mass Transfer limitations on species profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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real time simulation of dual layer catalytic converters based on the Internal Mass Transfer coefficient approach
Topics in Catalysis, 2017Co-Authors: J Rink, B Mozaffari, Steffen Tischer, Olaf Deutschmann, Martin VotsmeierAbstract:A new numerically efficient simulator for dual layer catalysts is implemented and its performance is demonstrated using the example of the dual layer ammonia oxidation catalyst. For the solution of the radial Mass balances, each washcoat layer is represented by a single volume element and the diffusive Mass fluxes into and within the washcoat are computed based on the concept of the Internal Mass Transfer coefficients. The performance of the new simulator is compared against a reference simulator that fully resolves the concentration profiles in the washcoat. For a steady state test case, the error introduced by the new solution scheme is below 2 % for all relevant exhaust components. For a transient test case, the deviations become more significant. For the simulation of a WHTC, the maximum deviation in the NH3 outlet concentration is 23.3 %, whereas the cumulated NH3 emissions deviate by 10.6 %.With the new simulator, the 1800 s of the transient WHTC cycle can be simulated within 53 s on a standard laptop, 30 times faster than real time.
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Mass Transfer Effects in Stagnation Flows on a Porous Catalyst: Water-Gas-Shift Reaction Over Rh/Al2O3
Zeitschrift für Physikalische Chemie, 2015Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract: Water-gas-shift(WGS)andreversewater-gas-shift(RWGS)reactionsarenumericallyinvestigatedinastagnation-flowonaporous Rh/Al 2 O 3 catalyst.Ex-ternalandInternalMassTransfereffectsarestudiedusingthreedifferentmodelsfortheMasstransportandchemicalconversioninsidetheporouscatalyst:thedusty-gasmodel,asetofreaction-diffusionequations,andtheeffectivenessfac-torapproach.Allthreemodelsarecoupledwiththeboundarylayerequationstodescribethepotentialflowonthestagnationdisc,andamulti-stepsurfacere-actionmechanismisimplemented.Thenumericallypredictedspeciesprofilesintheexternalboundarylayerarecomparedwithrecentlymeasuredprofiles.Inter-nalMassTransferlimitationsaremoresignificantthanexternalonesincaseofthe 100μm thickcatalystlayer.Theeffectsofcatalyststructure(thickness,meanporediameter,porosity,tortuosity)aswellasflowrateandpressureonchemicalconversionarediscussed. Keywords: Stagnation-Flow, External and Internal Mass Transfer, Water-Gas-ShiftReaction,ReverseWater-Gas-Shift,Rhodium,Dusty-GasModel,Reaction-Diffusion.
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Numerical modeling of stagnation-flows on porous catalytic surfaces: CO oxidation on Rh/Al2O3
Chemical Engineering Science, 2013Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract A stagnation-flow on a catalytic porous plate is modeled one-dimensionally coupled with multi-step surface reaction mechanisms and molecular transport (diffusion and conduction) in the flow field and the porous catalyst. Internal Mass transport inside the porous catalyst is studied with three different models: instantaneous diffusion (infinitely fast Mass transport), effectiveness factor, and one-dimensional reaction-diffusion equations. A new computer code, DETCHEM STAG , is presented to execute the numerical model. The oxidation of CO over a porous Rh/Al 2 O 3 surface is studied exemplarily. Experimental measurements are carried out to apply the developed model and the computer code. External and the Internal Mass Transfer effects in front of and inside the porous catalyst are discussed. Internal Mass Transfer limitations become important in case of a thick catalyst layer for accurately predicting the experimental results.
Canan Karakaya - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Methane and Propane Reforming Over a Porous Rh/Al$_{2}$O$_{3}$ Catalyst in Stagnation-Flows: Impact of Internal and External Mass Transfer Limitations on Species Profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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numerical simulation of methane and propane reforming over a porous rh al _ 2 o _ 3 catalyst in stagnation flows impact of Internal and external Mass Transfer limitations on species profiles
Catalysts, 2020Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al$_{2}$O$_{3}$ layer. A one-dimensional flow field is coupled with three models for Internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEM$^{STAG}$. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the Internal Mass Transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for Internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/Internal Mass Transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.
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Mass Transfer Effects in Stagnation Flows on a Porous Catalyst: Water-Gas-Shift Reaction Over Rh/Al2O3
Zeitschrift für Physikalische Chemie, 2015Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract: Water-gas-shift(WGS)andreversewater-gas-shift(RWGS)reactionsarenumericallyinvestigatedinastagnation-flowonaporous Rh/Al 2 O 3 catalyst.Ex-ternalandInternalMassTransfereffectsarestudiedusingthreedifferentmodelsfortheMasstransportandchemicalconversioninsidetheporouscatalyst:thedusty-gasmodel,asetofreaction-diffusionequations,andtheeffectivenessfac-torapproach.Allthreemodelsarecoupledwiththeboundarylayerequationstodescribethepotentialflowonthestagnationdisc,andamulti-stepsurfacere-actionmechanismisimplemented.Thenumericallypredictedspeciesprofilesintheexternalboundarylayerarecomparedwithrecentlymeasuredprofiles.Inter-nalMassTransferlimitationsaremoresignificantthanexternalonesincaseofthe 100μm thickcatalystlayer.Theeffectsofcatalyststructure(thickness,meanporediameter,porosity,tortuosity)aswellasflowrateandpressureonchemicalconversionarediscussed. Keywords: Stagnation-Flow, External and Internal Mass Transfer, Water-Gas-ShiftReaction,ReverseWater-Gas-Shift,Rhodium,Dusty-GasModel,Reaction-Diffusion.
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Numerical modeling of stagnation-flows on porous catalytic surfaces: CO oxidation on Rh/Al2O3
Chemical Engineering Science, 2013Co-Authors: Hüseyin Karadeniz, Steffen Tischer, Canan Karakaya, Olaf DeutschmannAbstract:Abstract A stagnation-flow on a catalytic porous plate is modeled one-dimensionally coupled with multi-step surface reaction mechanisms and molecular transport (diffusion and conduction) in the flow field and the porous catalyst. Internal Mass transport inside the porous catalyst is studied with three different models: instantaneous diffusion (infinitely fast Mass transport), effectiveness factor, and one-dimensional reaction-diffusion equations. A new computer code, DETCHEM STAG , is presented to execute the numerical model. The oxidation of CO over a porous Rh/Al 2 O 3 surface is studied exemplarily. Experimental measurements are carried out to apply the developed model and the computer code. External and the Internal Mass Transfer effects in front of and inside the porous catalyst are discussed. Internal Mass Transfer limitations become important in case of a thick catalyst layer for accurately predicting the experimental results.
Nikos G. Papayannakos - One of the best experts on this subject based on the ideXlab platform.
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Studying the Internal Mass Transfer phenomena inside a Ni/Al2O3 catalyst for benzene hydrogenation
Chemical Engineering Journal, 2008Co-Authors: Kostas C. Metaxas, Nikos G. PapayannakosAbstract:The Mass Transfer phenomena occurring inside Ni/Al2O3 catalytic extruidates have been studied for the liquid-phase hydrogenation of benzene. The experiments were conducted in a bench scale trickle-bed reactor at 17 bar absolute pressure and temperatures between 70 and 150 degrees C. Kinetic, thermodynamic and hydrodynamic effects have previously been examined [K.C. Metaxas, N.G. Papayarmakos, Ind. Eng. Chem. Res. 45(21) (2006) 7110-7119]. Temperature gradients inside the particle and across the liquid film surrounding catalyst particles have been checked and verified as absent. Concentration profiles of hydrogen and benzene show firstly that are consumed close to the surface of the extrudate and secondly to be in large excess along the particle radius. Catalyst particle tortuosity is estimated to be 3.75, very close to the value of 3.56 extracted from a statistical model based on nitrogen sorption hysteresis data. The effectiveness factor lies in the range of 0.19-0.35, implying strong diffusion limitations. The passivation of catalyst surface is posed as a solid reason for the modification of the true activation energy of the reaction occurred while moving from crushed catalyst particles to catalytic extruidates. (C) 2007 Elsevier B.V. All rights reserved
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Studying the Internal Mass Transfer phenomena inside a Ni/Al2O3 catalyst for benzene hydrogenation
Chemical Engineering Journal, 2007Co-Authors: Kostas C. Metaxas, Nikos G. PapayannakosAbstract:The Mass Transfer phenomena occurring inside Ni/Al2O3 catalytic extrudates have been studied for the liquid-phase hydrogenation of benzene. The experiments were conducted in a bench scale trickle-bed reactor at 17 bar absolute pressure and temperatures between 70 and 150 °C. Kinetic, thermodynamic and hydrodynamic effects have previously been examined [K.C. Metaxas, N.G. Papayannakos, Ind. Eng. Chem. Res. 45(21) (2006) 7110–7119]. Temperature gradients inside the particle and across the liquid film surrounding catalyst particles have been checked and verified as absent. Concentration profiles of hydrogen and benzene show firstly that are consumed close to the surface of the extrudate and secondly to be in large excess along the particle radius. Catalyst particle tortuosity is estimated to be 3.75, very close to the value of 3.56 extracted from a statistical model based on nitrogen sorption hysteresis data. The effectiveness factor lies in the range of 0.19–0.35, implying strong diffusion limitations. The passivation of catalyst surface is posed as a solid reason for the modification of the true activation energy of the reaction occurred while moving from crushed catalyst particles to catalytic extrudates.