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KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association
Institute for Chemical Technology and Polymer Chemistry (ITCP)
www.kit.edu
Institute for Catalysis Research and Technology (IKFT)
Microkinetic models for exhaust-gas after-treatment
Olaf Deutschmann, Karlsruhe Institute of Technology (KIT)
CLEERS 2015
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry2
THE CHALLENGE
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry3
Catalytic converter: Physics and chemistry on many scales
Courtesy of J. Eberspächer GmbH& Co
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry4
1 m10 s
1 mm10 ms
10 m 100 s10 nm1 nm0.1 nm
Catalytic converter:Physics and chemistry on many scales
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry5
THE DREAM
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry6
Simulation of catalytic reactors by multi-scale modeling:Information flux over the time and length scales
Complexity
Leng
thTi
me
Elementary reactions on surfaces
Particles and phases
Porous supports
Reactor behavior
DFT
kMC
Reactive flow
AdditivitySpill-over
Diffusion
Continuum mechanics
Transient models for heat and mass transfer
Multi componentParticle Sizes
Pt
Ce
Reactor behavior
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry7
THE REALITY
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry8
1 m10 s
1 mm10 ms
10 m 100 s10 nm1 nm0.1 nm
Catalytic converter:Physics and chemistry on many scales
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry9
Density Functional Theory (DFT):Understanding catalysis on a molecular level
0.1 nmJ.A. Keith, J. Anton, T.Jacob. Chapter 1 in Modeling and Simulation of HeterogeneousCatalytic Reactions. O. Deutschmann (Ed.), 2011
Energy barriers
Understanding reaction paths
Pre-screening of catalysts
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry10
Aging of Pd/Pt catalyst for CH4 total oxidation:Characterization by TEM and EDX
Total Pd/Pt loading 5:1
Most particles d < 5 nm Homogenous alloy
(Pd100Pt0 - Pd89±5Pt11±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 CH4, 10% O2
A. T. Gremminger, H. W. Pereira de Carvalho, R. Popescu, J.-D. Grunwaldt, O. Deutschmann. Catalysis Today (2015) DOI 10.1016/j.cattod.2015.01.034
CH4 + 2 O2 CO2 + 2 H2OPd/Pt
0 10 20 300
20
40
60
80
100
Pt L
Con
cent
ratio
n (a
t. %
)
x (nm)
Pd L
Probe 13: Pd-Pt/Al2O3 aged (Sp. 8)
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry11
Aging of Pd/Pt catalyst for CH4 total oxidation:Characterization by TEM and EDX
Total Pd/Pt loading 5:1
Most particles d < 5 nm Homogenous alloy
(Pd100Pt0 - Pd89±5Pt11±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 CH4, 10% O2
A. T. Gremminger, H. W. Pereira de Carvalho, R. Popescu, J.-D. Grunwaldt, O. Deutschmann. Catalysis Today (2015) DOI 10.1016/j.cattod.2015.01.034
CH4 + 2 O2 CO2 + 2 H2OPd/Pt
3 nm shellPd52±4Pt48±2
22 nm corePd5±3Pt95±2
• Total NP compositionPd36±5Pt64±6
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry12
Kinetic Monte Carlo Simulation of surface reactions and diffusion on catalytic particles: CO oxidation on Pt/Al2O3
1-100 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.), 2011
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry13
Effect of thermal aging on particle size distribution in DOC
Fresh DOC
DOC aged hydrothermally aging at 950°C
Particle size distribution
W. Boll, S. Tischer, O. Deutschmann, Ind. & Eng. Chem. Res. 49 (2010) 10303
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry14
Catalytic converter: Physics and chemistry on many scales
1 m10 s
1 mm10 ms
10 m 100 s10 nm1 nm0.1 nm
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry15
Modeling heterogeneous reactions: Concept of rate equations (mean-field approximation)
SR j
jk
ikijk
kcks
'
f
Surface reaction rate
ΓcΘ iii
Surface coverage
ΓMs
tΘ iii
Locally resolved reaction rates depending on gas-phase concentration and surface
coverages
O. Deutschmann. in Handbook of Heterogeneous Catalysis, 2nd Ed.,, G. Ertl, H. Knözinger, F. Schüth, J. Weitkamp (eds.), p. 1811, Wiley-VCH, 2008
Rate expression
s
1
expexpN
i
iiμi
aβkf RT
ΘεΘ
RTE
TAk kkikkk
= microscopic site density
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry16
Surface reaction kinetics of CO oxidation on Pt/Al2O3 DOC: Mean field approximation
D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental 156–157 (2014) 153.
Reaction coordinate
En
erg
y [k
J/m
ol]
-600
-500
-400
-300
-200
-100 free Pt surfaceCO coveredO covered
CO+O2
CO(Pt)+O2
CO(Pt)+O2(Pt)
CO2(Pt)+O(Pt)
CO(Pt)+2 O(Pt)
CO2+O(Pt)
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry17
D. Chatterjee, O. Deutschmann, J. Warnatz. Faraday Discuss. 119 (2001) 371J. Koop, O. Deutschmannn. Appl. Catal. B: Env. 91 (2009) 47
Proposed surface reaction mechanism for Pt/Rh-based three-way catalysts: Mean field approximation
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry18
Thermodynamic consistency
Development of micro kinetic models for simulations of catalytic reactors
Surface ScienceExperimental
Surface ScienceTheoretical
Reaction mechanismand kinetics (idea)
Modeling of lab reactors(including gas phase kinetics and
transport models)
Sensitivity & reaction flow analyses
Lab experiments(conversion, selectivity,
ignition/extinction temperatures,spatial & temporal profiles,
coverage)
Comparison of experiment and
simulation
Revised reaction mechanism
Technical reactor
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry19
Surface reaction rate is proportional
to the catalytic surface area
determined by CO-chemisorption
Pt particle sinteringAl2O3
Scaling factor:Scaling factor:
geocatcat
cat
geo
catgeocat AM
mDAAF
/
Modeling catalyst loading and dispersion:Variation of dispersion in a DOC due to aging
Pt particles
, cat/geo i s i i ij F M s
Ageo
Acat
AcatAgeoAcat
D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Env. 156–157 (2014) 153.
C. Karakaya, O. Deutschmann. Appl. Catal. A: Gen. 445-446 (2012) 221
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry20
Multi-scale modeling:From 10-10 m and 10-13 s to 1m and 10 s
1 m10 s
1 mm10 ms
10 m 100 s10 nm1 nm0.1 nm
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry21
Coupling of surface reaction rate and flow field -Modeling internal transport limitation of reaction rate
i
ii Φ
Φ )tanh(
0,,eff
ii
ii cD
sLΦ
Effectiveness factor
Thiele Modulus
, c a t /g e o i s i i ij F M s
fluid
washcoat
R.E. Hayes, B. Liu, M. Votsmeier. Chem. Eng. Sci. 60 (2005) 2037.
Simple model: effectiveness factor Reaction-diffusion equations
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry22
Multi-scale modeling:From 10-10 m and 10-13 s to 1m and 10 s
1 m10 s
1 mm10 ms
10 m 100 s10 nm1 nm0.1 nm
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry23
Impact of models for channel shape and washcoatdiffusion on NO profiles in a DOC
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) 812
no washcoatdiffusionlimitation
porousmediamodel
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry24
Development of micro kinetic models for simulations of catalytic reactors
Surface ScienceExperimental
Surface ScienceTheoretical
Reaction mechanismand kinetics (idea)
Lab experiments(conversion, selectivity,
ignition/extinction temperatures,spatial & temporal profiles,
coverage)
Modeling of lab reactors(including gas phase kinetics and
transport models)
Sensitivity & reaction flow analyses
Comparison of experiment and
simulation
Revised reaction mechanism
Thermodynamic consistency
Technical reactor
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry25
Development of micro kinetic models for simulations of catalytic reactors
Surface ScienceExperimental
Surface ScienceTheoretical
Reaction mechanismand kinetics (idea)
Lab experiments(conversion, selectivity,
ignition/extinction temperatures,spatial & temporal profiles,
coverage)
Modeling of lab reactors(including gas phase kinetics and
transport models)
Sensitivity & reaction flow analyses
Comparison of experiment and
simulation
Revised reaction mechanism
Thermodynamic consistency
Technical reactor
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry26
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, NO2, H2O, CO…
Temperature: RT – 700°C
Pressure: 1- 5 bar
Flow: 10 - 70 slpm
Gas analytics: FTIR, (MS)
www.abgaszentrum-karlsruhe.de
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry27
V. Schmeißer, J. Perez, U. Tuttlies, G. Eigenberger, Top. Catal. 42 (2007) 15
Isothermal flat bed reactor: Spatially and time-resolved exhaust-gas composition in catalyst channel
NO2 profile in NSC during storage
CO profile in DOC
J. Koop, O. Deutschmann. SAE 2007-01-1142.J. Koop, O. Deutschmann. Appl. Catal.B: Env. 91 (2009) 47
G. Eigenberger et al.
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry28
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, gas-
phase and surface temperatures (resolution: 0.25 mm)
Gases: Gaseous and liquid HCs, CO,
CO2, NH3, NO, NO2, O2,
Air, N2, H2, H2O
Temperature: RT – 1000°C
Pressure: 1 atm
Flow: 0.5 - 5 slpm
Gas analytics: FT- IR, MS, GC
D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental 156–157 (2014) 153.
G. Fisher et al., 2006R. 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) 2260.A. Donazzi, D. Livio, M. Maestri, A. Beretta, G. Groppi, E. Tronconi, P. Forzatti, Angew.
Chem. Int. Ed. 50 (2011) 3943.D. Livio, C. Diehm, A. Donazzi, A. Beretta, G. Groppi, O. Deutschmann, Appl. Catal. A
467 (2013) 530.
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Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry29
NO LIF profile during reduction by H2 to NH3 in Pt/Al2O3one-side-coated single channel of a DOC
A. Zellner, R. Suntz, O. Deutschmann, Angew. Chem. Intl. Ed. 54 (2015) 2653.
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
Lab test bench CATHLEN: Optical diagnostics of catalytic reactors
NO
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry30
Development of micro kinetic models for simulations of catalytic reactors
Surface ScienceExperimental
Surface ScienceTheoretical
Reaction mechanismand kinetics (idea)
Lab experiments(conversion, selectivity,
ignition/extinction temperatures,spatial & temporal profiles,
coverage)
Modeling of lab reactors(including gas phase kinetics and
transport models)
Sensitivity & reaction flow analyses
Comparison of experiment and
simulation
Revised reaction mechanism
Thermodynamic consistency
Technical reactor
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry31
Effect of catalyst loading on conversion of CO in DOCReaction flow analysis
D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental 156–157 (2014) 153.
440 460 480 500 520 540
0 2 4 6 8 10
T 50
[K]
Pt dispersion [%]
exp.sim.
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry32
Development of micro kinetic models for simulations of catalytic reactors
Surface ScienceExperimental
Surface ScienceTheoretical
Reaction mechanismand kinetics (idea)
Lab experiments(conversion, selectivity,
ignition/extinction temperatures,spatial & temporal profiles,
coverage)
Modeling of lab reactors(including gas phase kinetics and
transport models)
Sensitivity & reaction flow analyses
Comparison of experiment and
simulation
Revised reaction mechanism
Thermodynamic consistency
Technical reactor
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry33
Transient simulation of lab light-off experiment:Temporal variation of axial profiles during light-off
D. Chan, S. Tischer, J. Heck, C. Diehm, O. Deutschmann. Applied Catalysis B: Environmental 156–157 (2014) 153.
T = 508 K, Disp = 3%
0
0.2
0.4
0.6
0.8
1
400 450 500 550
CO
con
vers
ion
T [K]
exp.sim. eff.
sim. detailed
0
0.5
1
1.5
-3 0 3 6 9 12 15 18 21 24 27 30 6
7
8
9
CO [%
]
CO2 [
%]
z [mm]
CO exp.CO2 exp.
sim. eff.sim. detailed
z [mm]
CO(P
t)
5 10 15 20 250
0.2
0.4
0.6
0.8
t [min]
4367
z [mm]
CO2(P
t)
0 5 10 15 20 250
2E-07
4E-07
6E-07
8E-07
1E-06
1.2E-06
1.4E-06
t [min]50
4367
z [mm]
O(Pt
)
0 5 10 15 20 250
0.2
0.4
0.6
0.8
1
t [min]
50 4367
z [mm]
CO(P
t)
0 5 10 15 20 250
0.2
0.4
0.6
0.8
1
t [min]
435067
z [mm]
(Pt)
0 5 10 15 20 250
0.01
0.02
0.03
0.04
0.05
0.06
t [min]
4367 50
z [mm]
O 2(P
t)
0 5 10 15 20 250
1E-06
2E-06
3E-06
4E-06
5E-06
6E-06
7E-06
t [min]
4367
50
t [s]
T [K]
0 2000 4000
400
450
500
550
CO(Pt) CO
O2(Pt) O (Pt)
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry34
Development of micro kinetic models for simulations of catalytic reactors
Surface ScienceExperimental
Surface ScienceTheoretical
Reaction mechanismand kinetics (idea)
Lab experiments(conversion, selectivity,
ignition/extinction temperatures,spatial & temporal profiles,
coverage)
Modeling of lab reactors(including gas phase kinetics and
transport models)
Sensitivity & reaction flow analyses
Comparison of experiment and
simulation
Revised reaction mechanism
Thermodynamic consistency
Technical reactor
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry35
Pre-turbo SCR for large diesel engines:Effect of high pressure and temperature on conversion
C. Hauck, O. Deutschmann, 2014
cool
ai
r
LLK: charge air cooler DOC: diesel oxidation catalyst HK: hydrolysis catalystKMK: coolant cooler DPF: diesel particle filter SCR: SCR catalyst
SC: ammonia trap
charge airexhaustmain cooling circuit
diesel engine
turbo charger
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, 1514-1529
At constant mass flow:
Residence time ~ pressureDiffusion ~ 1/pressure
L ~ 22 cm
1 bar
5 bar
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry36
Multi-scale modeling:From 10-10 m and 10-13 s to 1m and 10 s
1 m10 s
1 mm10 ms
10 m 100 s10 nm1 nm0.1 nm
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry37
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 2002-01-0065
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry38
DETCHEMMONOLITH: Computer program for the numerical simulation of transients in catalytic monoliths
MONOLITHTemperature of the solid structure incl. canning
by a 2D / 3D heat balance
CHANNEL or PLUG 1D or 2D-flow field simulations for a representative number of
channels using boundary layer or plug flow equations
temperature profileat the wall heat source term
time scale ~ 1 s
residence time < 100 msquasi-steady-statetransient
gas phase concentrationstemperature
chemical source termtransport coefficients
DETCHEM - LibraryThermodynamic and transport properties
Detailed reaction mechanisms for gas-phase & surface
S. Tischer, O. Deutschmann, Catal. Today 105 (2005) 407, www.detchem.de
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry39
Cumulative CO emission in MEVG cycle:Experiment vs. simulation
0
1
2
3
4
5
6
7
8
0 200 400 600 800 1000 1200time [s]
CO
em
issi
on [%
]
0
20
40
60
80
100
cum
ulat
ive
CO
em
issi
on [g
]
inletinlet (cum.)experiment (cum.)simulation (cum.)
Tischer et al. SAE Technical paper 2007-01-1072 2007
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry40
2 NH3 + NO + NO2 2 N2 + 3 H2O
Selective catalytic reduction (SCR) of NOx emissions by urea solution: Processes between injection and catalyst
(NH2)2CO (l) NH3 (g) + HNCO (g)HNCO (g) + H2O (g) NH3 (g) + CO2 (g)
F. Birkhold, U. Meingast, P. Wassermann, O. Deutschmann. SAE Technical paper 2006-01-0643, SAE 2006 Trans. J. of Fuels and Lubricants (2006), 252F. Birkhold, U. Meingast, P. Wassermann, O. Deutschmann. Appl. Catal. B: Environmental 70 (2007) 119-127
Source: Robert Bosch GmbH
deposit
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry41
W. Brack, B. Heine, F. Birkhold, M. Kruse, G. Schoch, S. Tischer, O. Deutschmann. Chem. Eng. Sci. 106 ( 2014)1–8.
Modeling of deposit formation in Urea-SCR:Understanding the reaction mechanism
Source: Robert Bosch GmbH
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry42
Simulation of catalytic converters from first principles:Dream or nightmare?
Complexity
Leng
thTi
me
Elementary reactions on surfaces
Particles and phases
Porous supports
Reactor behavior
DFT
kMC
Reactive flow
AdditivitySpill-over
Diffusion
Continuum mechanics
Transient models for heat and mass transfer
Multi componentParticle Sizes
Pt
Ce
Reactor behavior
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry43
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)
SFB/TRR 150 (TU Darmstadt, KIT)Deutschmann group at KIT 2011
Funding and industry partners
Dr. Denise Chan A. Gremminger Dr. Claudia Diehm Wolfgang Brack Dr. Ch. Hauck Dr. Luba Maier Dr. SteffenTischer
-
Olaf Deutschmann
Institute for Chemical Technology and Polymer Chemistry44
Thank you!Abstract due May 15
J. Emission Control Sci. & Technol. Paper due Aug 31
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