Microkinetic models for exhaust-gas after-treatment

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1 Microkinetic models for exhaust-gas after-treatment, Karlsruhe Institute of Technology (KIT) CLEERS 2015 (ITCP) Institute for Catalysis Research and Technology (IKFT) KIT University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

2 THE CHALLENGE 2

3 Catalytic converter: Physics and chemistry on many scales Courtesy of J. Eberspächer GmbH& Co 3

4 Catalytic converter: Physics and chemistry on many scales 1 m 10 s 1 mm 10 ms 0.1 nm 1 nm 10 nm 10 m 100 s 4

5 THE DREAM 5

Pt Continuum mechanics Diffusion Reactor behavior Reactive flow kmc Porous supports DFT Ce

6 Simulation of catalytic reactors by multi-scale modeling: Information flux over the time and length scales Transient models for heat and mass transfer Length Time Additivity Spill-over Pt Continuum mechanics Diffusion Reactor behavior Reactive flow kmc Porous supports DFT Ce Multi component Particle Sizes Particles and phases Elementary reactions on surfaces Complexity 6

7 THE REALITY 7

8 Catalytic converter: Physics and chemistry on many scales 1 m 10 s 1 mm 10 ms 0.1 nm 1 nm 10 nm 10 m 100 s 8

9 Density Functional Theory (DFT): Understanding catalysis on a molecular level 0.1 nm J.A. Keith, J. Anton, T.Jacob. Chapter 1 in Modeling and Simulation of Heterogeneous Catalytic Reactions. O. Deutschmann (Ed.), 2011 Energy barriers Understanding reaction paths Pre-screening of catalysts 9

10 Aging of Pd/Pt catalyst for CH 4 total oxidation: Characterization by TEM and EDX CH O 2 Pd/Pt CO H 2 O Total Pd/Pt loading 5:1 Most particles d < 5 nm Homogenous alloy (Pd 100 Pt 0 -Pd 89±5 Pt 11±2 ) Some particles d 10 nm Homogenous Alloy, higher Pt-content Few large particles d > 30 nm Homogenous alloy High Pt content Formation of core-shell structure after 100 h, 1000 ppm CH 4, 10% O 2 A. T. Gremminger, H. W. Pereira de Carvalho, R. Popescu, J.-D. Grunwaldt, O. Deutschmann. Catalysis Today (2015) DOI /j.cattod Concentration (at. %) Probe 13: Pd-Pt/Al 2 O 3 aged (Sp. 8) Pt L Pd L x (nm)

Aging of Pd/Pt catalyst for CH 4 total oxidation: Characterization by TEM and EDX CH 4 + 2 O 2 Pd/Pt CO 2 + 2 H 2 O Total Pd/Pt loading 5:1 Most particles d < 5 nm Homogenous alloy (Pd 100 Pt 0 -Pd

11 Aging of Pd/Pt catalyst for CH 4 total oxidation: Characterization by TEM and EDX CH O 2 Pd/Pt CO H 2 O Total Pd/Pt loading 5:1 Most particles d < 5 nm Homogenous alloy (Pd 100 Pt 0 -Pd 89±5 Pt 11±2 ) Some particles d 10 nm Homogenous Alloy, higher Pt-content Few large particles d > 30 nm Homogenous alloy High Pt content Formation of core-shell structure after 100 h, 1000 ppm CH 4, 10% O 2 Total NP composition Pd 36±5 Pt 64±6 3 nm shell Pd 52±4 Pt 48±2 22 nm core Pd 5±3 Pt 95±2 A. T. Gremminger, H. W. Pereira de Carvalho, R. Popescu, J.-D. Grunwaldt, O. Deutschmann. Catalysis Today (2015) DOI /j.cattod

Kinetic Monte Carlo Simulation of surface reactions and diffusion on catalytic particles: CO oxidation on Pt/Al 2 O 3 1-100 nm Coverage over time on each facet

12 Kinetic Monte Carlo Simulation of surface reactions and diffusion on catalytic particles: CO oxidation on Pt/Al 2 O nm Coverage over time on each facet Reaction rates of each process Number of times each process was used L. Kunz et al., Chapter 4 in Modeling Heterogeneous Catalytic Reactions. O. Deutschmann (Ed.),

hydrothermally aging at 950 C W. Boll, S. Tischer, O.

13 Effect of thermal aging on particle size distribution in DOC Fresh DOC Particle size distribution DOC aged hydrothermally aging at 950 C W. Boll, S. Tischer, O. Deutschmann, Ind. & Eng. Chem. Res. 49 (2010)

14 Catalytic converter: Physics and chemistry on many scales 1 m 10 s 1 mm 10 ms 0.1 nm 1 nm 10 nm 10 m 100 s 14

gas-phase concentration and surface coverages 15 Rate expression E β a k k f AkT exp k RT k N s i 1 Θ μ i ik εi Θ k exp RT i O.

15 Modeling heterogeneous reactions: Concept of rate equations (mean-field approximation) Surface coverage Θ i Surface reaction rate s i ci i Γ k R k ik Θ t f k i i j S s M Γ c j ' jk i = microscopic site density Locally resolved reaction rates depending on gas-phase concentration and surface coverages 15 Rate expression E β a k k f AkT exp k RT k N s i 1 Θ μ i ik εi Θ k exp RT i O. Deutschmann. in Handbook of Heterogeneous Catalysis, 2nd Ed.,, G. Ertl, H. Knözinger, F. Schüth, J. Weitkamp (eds.), p. 1811, Wiley-VCH, 2008

Surface reaction kinetics of CO oxidation on Pt/Al 2 O 3 DOC: Mean field approximation CO+O 2-100 free Pt surface CO covered O covered -200 Energy [kj/mol] -300-400 CO(Pt) +O 2 CO(Pt) +O 2

16 Surface reaction kinetics of CO oxidation on Pt/Al 2 O 3 DOC: Mean field approximation CO+O free Pt surface CO covered O covered -200 Energy [kj/mol] CO(Pt) +O 2 CO(Pt) +O 2 (Pt) CO(Pt) +2 O(Pt) CO 2 (Pt) +O(Pt) CO 2 +O(Pt) Reaction coordinate D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental (2014)

17 Proposed surface reaction mechanism for Pt/Rh-based three-way catalysts: Mean field approximation D. Chatterjee, O. Deutschmann, J. Warnatz. Faraday Discuss. 119 (2001) 371 J. Koop, O. Deutschmannn. Appl. Catal. B: Env. 91 (2009) 47 17

18 Development of micro kinetic models for simulations of catalytic reactors Surface Science Experimental Reaction mechanism and kinetics (idea) Surface Science Theoretical Modeling of lab reactors (including gas phase kinetics and transport models) Lab experiments (conversion, selectivity, ignition/extinction temperatures, spatial & temporal profiles, coverage) Comparison of experiment and simulation Thermodynamic consistency Technical reactor Sensitivity & reaction flow analyses Revised reaction mechanism 18

Modeling catalyst loading and dispersion:

catalytic surface area A cat determined by

19 Modeling catalyst loading and dispersion: Variation of dispersion in a DOC due to aging Al 2 O 3 Pt particle Pt particles sintering D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Env (2014) 153. A geo Scaling factor: A cat F cat / geo A A cat geo D M cat m cat cat A geo Surface reaction rate is proportional to the catalytic surface area A cat determined by CO-chemisorption C. Karakaya, O. Deutschmann. Appl. Catal. A: Gen (2012) 221 j F M s is, i cat/geo i i A geo A cat 19

20 Multi-scale modeling: From m and s to 1m and 10 s 1 m 10 s 1 mm 10 ms 0.1 nm 1 nm 10 nm 10 m 100 s 20

21 Coupling of surface reaction rate and flow field - Modeling internal transport limitation of reaction rate washcoat R.E. Hayes, B. Liu, M. Votsmeier. Chem. Eng. Sci. 60 (2005) Simple model: effectiveness factor Reaction-diffusion equations Thiele Modulus Φ i L s D i c eff, i i,0 fluid Effectiveness factor i tanh(φ i) Φ i j F M s i, s i cat/geo i i 21

22 Multi-scale modeling: From m and s to 1m and 10 s 1 m 10 s 1 mm 10 ms 0.1 nm 1 nm 10 nm 10 m 100 s 22

Impact of models for channel shape and washcoat diffusion on NO profiles in a DOC no washcoat diffusion limitation porous media model NO profiles at lean

23 Impact of models for channel shape and washcoat diffusion on NO profiles in a DOC no washcoat diffusion limitation porous media model NO profiles at lean conditions at 250 C (steady-state operation) CFD code: Fluent + DETCHEM N. Mladenov, J. Koop, S. Tischer, O. Deutschmann. Chem. Eng. Sci. 65 (2010)

24 Development of micro kinetic models for simulations of catalytic reactors Surface Science Experimental Reaction mechanism and kinetics (idea) Surface Science Theoretical Modeling of lab reactors (including gas phase kinetics and transport models) Lab experiments (conversion, selectivity, ignition/extinction temperatures, spatial & temporal profiles, coverage) Comparison of experiment and simulation Thermodynamic consistency Technical reactor Sensitivity & reaction flow analyses Revised reaction mechanism 24

25 Development of micro kinetic models for simulations of catalytic reactors Surface Science Experimental Reaction mechanism and kinetics (idea) Surface Science Theoretical Modeling of lab reactors (including gas phase kinetics and transport models) Lab experiments (conversion, selectivity, ignition/extinction temperatures, spatial & temporal profiles, coverage) Comparison of experiment and simulation Thermodynamic consistency Technical reactor Sensitivity & reaction flow analyses Revised reaction mechanism 25

54 cm, length < 6cm) Labview automatic controlled measurements Coated pipes, reactor and

26 Lab test benches in the Exhaust-Gas Center Karlsruhe: High-Pressure setup Tests of catalyst coated honeycombs (d = 2.54 cm, length < 6cm) Labview automatic controlled measurements Coated pipes, reactor and analytics for sulfur Gases: NO, NO 2, H 2 O, CO Temperature: RT 700 C Pressure: 1-5 bar Flow: slpm Gas analytics: FTIR, (MS) 26

27 Isothermal flat bed reactor: Spatially and time-resolved exhaust-gas composition in catalyst channel CO profile in DOC G. Eigenberger et al. NO 2 profile in NSC during storage J. Koop, O. Deutschmann. SAE J. Koop, O. Deutschmann. Appl. Catal.B: Env. 91 (2009) V. Schmeißer, J. Perez, U. Tuttlies, G. Eigenberger, Top. Catal. 42 (2007) 15

Lab test bench SpaciPro: Invasive in-situ technique for axially resolved profiles Tests of catalytically coated honeycombs (d = 2-2,54 cm, length ~ 5 cm) Axially resolved profiles of species

28 Lab test bench SpaciPro: Invasive in-situ technique for axially resolved profiles Tests of catalytically coated honeycombs (d = 2-2,54 cm, length ~ 5 cm) Axially resolved profiles of species concentration, gasphase and surface temperatures (resolution: 0.25 mm) Gases: Gaseous and liquid HCs, CO, CO 2, NH 3, NO, NO 2, O 2, Air, N 2, H 2, H 2 O Temperature: RT 1000 C Pressure: 1 atm Flow: slpm Gas analytics: FT- IR, MS, GC D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental (2014) 153. G. Fisher et al., 2006 R. Horn, N. J. Degenstein, K. A. Williams, L. D. Schmidt, Catal. Lett. 110 (2006) 169. J. Sá, D.L. Abreu Fernandes, F. Aiouache, A. Goguet, C. Hardacre, D. Lundie, W. Naeem, W.P. Partridge, C. Stere, Analyst 135 (2010) A. Donazzi, D. Livio, M. Maestri, A. Beretta, G. Groppi, E. Tronconi, P. Forzatti, Angew. Chem. Int. Ed. 50 (2011) D. Livio, C. Diehm, A. Donazzi, A. Beretta, G. Groppi, O. Deutschmann, Appl. Catal. A 467 (2013)

29 Lab test bench CATHLEN: Optical diagnostics of catalytic reactors Non-invasive in-situ analysis of spatial and temporal profiles of species concentration and temperature in the gas phase above a catalytic surface using Raman and LIF-spectroscopy NO LIF profile during reduction by H 2 to NH 3 in Pt/Al 2 O 3 one-side-coated single channel of a DOC NO A. Zellner, R. Suntz, O. Deutschmann, Angew. Chem. Intl. Ed. 54 (2015)

30 Development of micro kinetic models for simulations of catalytic reactors Surface Science Experimental Reaction mechanism and kinetics (idea) Surface Science Theoretical Modeling of lab reactors (including gas phase kinetics and transport models) Lab experiments (conversion, selectivity, ignition/extinction temperatures, spatial & temporal profiles, coverage) Comparison of experiment and simulation Thermodynamic consistency Technical reactor Sensitivity & reaction flow analyses Revised reaction mechanism 30

31 Effect of catalyst loading on conversion of CO in DOC Reaction flow analysis T 50 [K] exp. sim Pt dispersion [%] D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental (2014)

32 Development of micro kinetic models for simulations of catalytic reactors Surface Science Experimental Reaction mechanism and kinetics (idea) Surface Science Theoretical Modeling of lab reactors (including gas phase kinetics and transport models) Lab experiments (conversion, selectivity, ignition/extinction temperatures, spatial & temporal profiles, coverage) Comparison of experiment and simulation Thermodynamic consistency Technical reactor Sensitivity & reaction flow analyses Revised reaction mechanism 32

33 Transient simulation of lab light-off experiment: Temporal variation of axial profiles during light-off 1.5 T = 508 K, Disp = 3% 9 CO CO(Pt) CO [%] 1 8 CO exp. 0.5 CO 2 exp. sim. eff. 7 sim. detailed z [mm] CO 2 [%] 1 CO conversion exp. sim. eff. sim. detailed T [K] 1 1.4E-06 CO(Pt) t [min] 43 CO 2 (Pt) 1.2E-06 1E-06 8E-07 6E t [min] E-07 2E z [mm] z [mm] 1 7E-06 O(Pt) t [min] O 2 (Pt) 6E-06 5E-06 4E-06 3E t [min] E-06 1E z [mm] z [mm] (Pt) t [min] z [mm] T [K] t [s] O 2 (Pt) D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental (2014) 153. O(Pt) 33

34 Development of micro kinetic models for simulations of catalytic reactors Surface Science Experimental Reaction mechanism and kinetics (idea) Surface Science Theoretical Modeling of lab reactors (including gas phase kinetics and transport models) Lab experiments (conversion, selectivity, ignition/extinction temperatures, spatial & temporal profiles, coverage) Comparison of experiment and simulation Thermodynamic consistency Technical reactor Sensitivity & reaction flow analyses Revised reaction mechanism 34

Pre-turbo SCR for large diesel engines: Effect of high pressure and temperature on conversion turbo charger At constant mass flow: cool air diesel engine charge air exhaust main cooling circuit

35 Pre-turbo SCR for large diesel engines: Effect of high pressure and temperature on conversion turbo charger At constant mass flow: cool air diesel engine charge air exhaust main cooling circuit Residence time ~ pressure Diffusion ~ 1/pressure LLK: charge air cooler DOC: diesel oxidation catalyst HK: hydrolysis catalyst KMK: coolant cooler DPF: diesel particle filter SCR: SCR catalyst SC: ammonia trap L ~ 22 cm 1 bar 5bar E. Tronconi, I. Nova, C. Ciardelli, D. Chatterjee, M. Weibel; J. Catal. 245 (2007) 1. I. Nova, C. Ciardelli, E. Tronconi, D. Chatterjee, M. Weibel; (2009), AIChE J.55, 6, C. Hauck, O. Deutschmann, 2014

36 Multi-scale modeling: From m and s to 1m and 10 s 1 m 10 s 1 mm 10 ms 0.1 nm 1 nm 10 nm 10 m 100 s 36

37 Simulation at real driving conditions is very challenging: Continuous variation of all inlet variables J. Braun, T. Hauber, H. Többen, J. Windmann, P. Zacke, D. Chatterjee, C. Correa, O. Deutschmann, L. Maier, S.Tischer, J. Warnatz, SAE paper

DETCHEM MONOLITH : Computer program for the numerical simulation of transients in

or 2D-flow field simulations for a representative number of channels using boundary

transport coefficients DETCHEM - Library Thermodynamic and transport properties

38 DETCHEM MONOLITH : Computer program for the numerical simulation of transients in catalytic monoliths MONOLITH Temperature of the solid structure incl. canning by a 2D / 3D heat balance transient quasi-steady-state temperature profile at the wall heat source term time scale ~ 1 s residence time < 100 ms CHANNEL or PLUG 1D or 2D-flow field simulations for a representative number of channels using boundary layer or plug flow equations gas phase concentrations temperature chemical source term transport coefficients DETCHEM - Library Thermodynamic and transport properties Detailed reaction mechanisms for gas-phase & surface S. Tischer, O. Deutschmann, Catal. Today 105 (2005) 407, 38

39 Cumulative CO emission in MEVG cycle: Experiment vs. simulation CO emission [%] inlet inlet (cum.) experiment (cum.) simulation (cum.) cumulative CO emission [g] time [s] Tischer et al. SAE Technical paper

Selective catalytic reduction (SCR) of NO x emissions by urea solution: Processes

(g) NH 3 (g) + CO 2 (g) Source: Robert Bosch GmbH 2 NH 3 + NO + NO 2 2 N 2 + 3 H 2 O

SAE Technical paper 2006-01-0643, SAE 2006 Trans. J.

40 Selective catalytic reduction (SCR) of NO x emissions by urea solution: Processes between injection and catalyst (NH 2 ) 2 CO (l) NH 3 (g) + HNCO (g) HNCO (g) + H 2 O (g) NH 3 (g) + CO 2 (g) Source: Robert Bosch GmbH 2 NH 3 + NO + NO 2 2 N H 2 O deposit F. Birkhold, U. Meingast, P. Wassermann, O. Deutschmann. SAE Technical paper , SAE 2006 Trans. J. of Fuels and Lubricants (2006), 252 F. Birkhold, U. Meingast, P. Wassermann, O. Deutschmann. Appl. Catal. B: Environmental 70 (2007)

41 Modeling of deposit formation in Urea-SCR: Understanding the reaction mechanism Source: Robert Bosch GmbH W. Brack, B. Heine, F. Birkhold, M. Kruse, G. Schoch, S. Tischer, O. Deutschmann. Chem. Eng. Sci. 106 ( 2014)

42 Simulation of catalytic converters from first principles: Dream or nightmare? Transient models for heat and mass transfer Length Time Additivity Spill-over Pt Continuum mechanics Diffusion Reactor behavior Reactive flow kmc Porous supports DFT Ce Multi component Particle Sizes Particles and phases Elementary reactions on surfaces Complexity 42

43 Acknowledgements - Exhaust-Gas After-Treatment Academic collaborations J.-D. Grunwaldt & many colleagues at KIT U. Nieken, G. Eigenberger (U Stuttgart) E. Tronconi (Politecnico Milano) R. Gläser (U Leipzig) Ch. Beidel, (TU Darmstadt) G. Wachtmeister (TU München) Deutschmann group at KIT 2011 SFB/TRR 150 (TU Darmstadt, KIT) Dr. Denise Chan A. Gremminger Dr. Claudia Diehm Wolfgang Brack Dr. Ch. Hauck Dr. Luba Maier Dr. SteffenTischer Funding and industry partners 43

44 Abstract due May 15 Thank you! J. Emission Control Sci. & Technol. Paper due Aug 31 44

What happens inside? Spatial resolution techniques for catalytic reactors

What happens inside? Spatial resolution techniques for catalytic reactors, Karlsruhe Institute of Technology (KIT) ESCRE 2015, 28.10.2015, Fürstenfeldbruck, Germany (ITCP) Institute for Catalysis Research