Predictive Theoretical Elementary Reaction Kinetics and ...
Transcript of Predictive Theoretical Elementary Reaction Kinetics and ...
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Predictive Theoretical
Elementary Reaction Kinetics and its
Role in Combustion Modeling
Stephen J. Klippenstein
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Theoretical Elementary Reaction Kinetics Potential Energy Surface Exploration
Ab Initio Electronic Structure Theory Stationary Points – Minima and Transition States Evaluate Energies and Rovibrational Properties
Predict Rate Constants for Individual Dynamical Steps Transition State Theory (TST) Evaluate Partition Functions Tunneling, Hindered Rotors, Variational Effects
Predict Collision Induced Energy Transfer Rates Collision Rate Energy Transfer Distribution Usually Empirical
Predict/Model Pressure Dependence Master Equation -> Population vs. Time Represent with Kinetic Phenomenology
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Ab Initio Transition State Theory Master Equation
Lawrence B. Harding Yuri Georgievskii James A. Miller
Team Effort How to Calculate Rate Constants Accurately and Efficiently?
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Energy Transfer Applications
Ahren Jasper Judit Zador
AITSTME Coding Team
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Outline
1. Theoretical Studies Motivated by Modeling • CO + HO2, H + HO2, CH3OH + HO2 • NNH Chemistry • CH2 + O2 • C3H6OOH + O2 • C4H9OH, C4H9O, C4H9O + O2
2. Uncertainties • Electronic Energies • Vibrational Frequencies • Torsional Modes • Energy Transfer • Coupling of TST and Energy Transfer
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CO/H2/O2 Oxidation: Ignition Delays in RCM
G. Mittal, C. J. Sung, R. A. Yetter, Int. J. Chem. Kinet. 38, 516 (2006).
Uncertainty Analysis Highlighted Sensitivity to CO + HO2 G. Mittal, C. J. Sung, M. Fairweather, A. S. Tomlin, J. F. Griffiths, K. J. Hughes, Proc. Comb. Inst. 31, 419 (2007).
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CO + HO2 -> CO2 + OH
You, Wang, Goos, Sung, Klippenstein, J. Phys. Chem. A, 111, 4031 (2007)
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H2/O2 at High Pressure
-2 -1 0 1 2
Sensitivity Coefficient
phi=2.5
phi=1.0
phi=0.3
H+OH+M=H2O+M
O+H2=H+OH HO2+OH=H2O+O2
HO2+H=H2+O2
H2+OH=H2O+H
HO2+H=OH+OH H+O2=O+OH
H+O2(+M)=HO2(+M)
H2/O2/He, Tf~1400K10 atm
Burke, Chaos, Ju, Dryer, Klippenstein, Int. J. Chem. Kinet. 44, 444 (2012).
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H + HO2 Recombination
1e-11
1e-10
0 500 1000 1500 2000
HO2 + H -> H
2O
2
PT2/dzPT2/adzLi 2007k
(cm
3 mol
ecul
e-1 s
-1)
Temperature (K)
Direct CASPT2 Variable Reaction Coordinate TST Calculations ~ 20% Uncertainty Validate Modeling Determined Rate
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The Role of NNH in NO Formation and Control NNH Life(me – Discrepancy between value required for
modeling and value predicted by theory NNH Mechanism for NOx Forma(on – Possibly important at
low temperatures 1. NNH + O2
2. NNH + O; NH + NO, H + N2O 3. NH2 + O2 -‐> H2NO + O 4. Literature Review of NNH Life(me and
Thermochemistry 5. More accurate branching ra(os for NH2 + NO S. J. Klippenstein, L. B. Harding, P. Glarborg, and J. A. Miller, Comb. Flame, 158, 774 (2011).
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Modeling vs Expt NO O2 and T Dependence
Experiments: F. Kasuya, P. Glarborg, K. Dam-Johansen, Chem. Eng. Sci. 50 (1995) 1455-1466.
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Modeling vs Expt N2O O2 and T Dependence
Inlet concentrations: NO = 500 +/- 30 ppm NH3 = 1000 +/- 60 ppm H2O = 5% balance N2 F. Kasuya, P. Glarborg, K. Dam-Johansen, Chem. Eng. Sci. 50 (1995) 1455-1466.
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Modeling vs Expt NO2 O2 and T Dependence
Inlet concentrations: NO = 500 +/- 30 ppm NH3 = 1000 +/- 60 ppm H2O = 5% balance N2 F. Kasuya, P. Glarborg, K. Dam-Johansen, Chem. Eng. Sci. 50 (1995) 1455-1466.
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Modeling vs Expt NO H2 and T Dependence
Inlet concentrations: NO = 500 +/- 30 ppm NH3 = 1000 +/- 60 ppm H2O = 5% balance N2 W. Duo, K. DamJohansen, K. Ostergaard, Can. J. Chem. Eng. 70 (1992) 1014-1020.
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Mechanism Development C0-C3 Core Mechanism
Large scale update of Miller mechanism Include Pressure Dependent Rate Coefficients
1x10-13
1x10-12
1x10-11
1x10-10
0 1 2 3 4 5
Sing;CISing;PT2Trip;CITrip;PT2Sum;CISum;PT2
VinckierBleyDombrowskyBohlandLauferPilling
k (c
m3 m
olec
ule-1
s-1
)
1000/T
3CH2 + O2
Miller, Klippenstein, and Glarborg, work in progress
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Pressure Dependent Reactions QOOH + O2
Modeling indicates QOOH + O2 Central to Low Temperature Chain Branching but essentially no Elementary Kinetics Studies C3H6OOH + O2 Smallest Prototype Goldsmith, Green, Klippenstein, J. Phys. Chem. A, 116, 3325 (2012)
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Butanol Chemistry
CEFRC Developing Mechanism for Butanol Combustion Sensitivity Analyses Suggest Need for Further Study of a Few Key Reactions C4H9OH Decomposition - Isobutanol
C. W. Zhou, S. J. Klippenstein, J. M. Simmie, H. J. Curran, Proc. Comb. Inst. in press (2012); Paper 4D05 C4H9O Decomposition (α, β, γ, δ, and O radicals)
P. Zhang, C. K. Law, S. J. Klippenstein, (2012). C4H9O + O2 (α, β, γ, and δ radicals)
O. Welz, J. Zador, S. J. Klippenstein, in progress (2012).
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Sensitivity for Methanol (CH3OH) Combustion Li, Zhao, Kazakov, Chaos, Dryer, Scire, IJCK, 39, 109 (2007)
Validated Against Igni(on Delays, Flame Speeds, Species Profiles
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How to Improve for Engine Conditions - High Pressures/Non-Dilute?
Klippenstein, Harding, Davis, Tomlin, Skodje Proc. Comb. Inst. 33, 351 (2011).
Variance Analysis for the Ignition Delay
Global uncertainty analysis • Indicates reaction with
dominant contribution to overall uncertainty
• Theoretical predictions of selected rate coefficients
• How accurate?
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Transition State Theory Complete torsional sampling to find torsional minima Torsional modes treated as uncoupled 1-dimensional hindered rotors Asymmetric Eckart Tunneling Other modes – harmonic oscillators and rigid rotors
CH3OH + HO2
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Change in ignition characteristics
Width/<τ> Ini(al 2.0 Final 0.70
<τ> Ini(al 0.11 Final 0.40
Final Uncertainty Analysis Predicted Ignition Delays
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How Accurate are our Predictions? Currently a Factor of 2-‐3 Uncertainty Compare with Experiments
– Experience from many comparisons Analysis of uncertainty for underlying factors in
theore(cal analysis – Barrier Height Uncertain(es – Vibra(onal Frequency Uncertain(es – Anharmonicity Correc(ons
Do Mechanisms Improve? Trying to reduce uncertain(es to about 1.2-‐1.3
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Reactions with Barriers
1
2
3
4
600 800 1000 1200 1400
Boltzmann Factors for Given Errors (kcal/mol)
Error=0.2Error=0.3Error=0.5Error=0.7Error=1.Error=1.5Error=2.
Boltz
man
n Fa
ctor
Temperature (K)
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Combustion Thermochemistry Database
HEAT (Stanton and coworkers); Wn (Martin and coworkers); Focal Point (Allen and coworkers)
CCSD(T)/TZ optimizations and Frequencies CCSD(T)/CBS from CCSD(T)/AQZ’,A5Z’ CCSDT(Q)/DZ Core-Valence CCSD(T)/CBS; TZ and QZ Relativistic from DKH with CI/TZ DBOC from HF/cc-pVTZ Anharmonic corrections from B3LYP/6-311++G** Heats of formation relative to H2, CH4, H2O, NH3
5 Heavy Atoms
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Size of Individual Corrections
Mean MAD RMSD Variance CCSDT(Q) -0.36 0.42 0.62 0.46 Core-Valence 0.54 0.54 0.60 0.28 Anharmonicity 0.47 0.49 0.59 0.32 Relativistic -0.16 0.16 0.20 0.11 DBOC 0.10 0.11 0.14 0.09
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Accuracy vs ATcT from Ruscic H, O, OH, O2, HO2, H2O2, O3, C, CH, CH2, 1CH2, CH3, CO, HCO, COH, CH2O, HCOH, CH2OH, CH3O, CO2, HOCO, HCO2, OCHOH, CH3O2, CH3OOH, C2, C2H2, H2CC, C2H3, CCH3, C2H4, CHCH3, C2H5, C2H6, CCO, 1CCO, HCCO, CH2CO, HCCOH, CH3CO, CH3CHO, CH2CHOH, CH3CHOH, C2H4OH, CH3CH2O, C2H5OH, CH3OCH3, OCHCHO, CH3C(O)OH, CH2CCH, CH3CCH, CH2CCH2, -CH2CHCH-, CH3CHCH2, CH3CH2CH3, N, NNH, NHNH, H2NN, NHNH2, NH2NH2, NO, HNO, NOH, H2NO, HNOH, H2NOH, N2O, NO2, NO3, CN, HCN, CNH, H2CN, HCNH, CH3N, CH2NH, CH3NH, CH2NH2, CH3NH2, NCO, HNCO, HCNO, NCOH
0
5
10
15
20
25
30
0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75
Heat of Formation Errors
With CorrectionsWithout Corrections
Num
ber
kcal/mol
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Rovibrational Properties Reactions on C3H7 PES
0.2
0.4
0.6
0.8
1
1.2
400 600 800 1000 120014001600 18002000
QCISD(T)/CBS//M06-2X//6-311++G(d,p)
n->ii->nn->CH3+C2H4CH3+C2H4->n
n->H+C3H6H+C3H6->ni->C3H6+HH+C3H6->i
k / k
QC
I//C
C/T
Z
Temperature (K)
1
10
400 600 800 1000 120014001600 18002000
QCISD(T)/CBS//B3LYP/6-311++G(d,p)
n->ii->nn->CH3+C2H4CH3+C2H4->n
n->H+C3H6H+C3H6->ni->C3H6+HH+C3H6->i
k / k
QC
I//C
C/T
Z
Temperature (K)
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Rovibrational Properties
0.8
1
1.2
1.4
1.6
1.8
2
2.2
400 600 800 1000 120014001600 18002000
QCISD(T)/CBS//PT2/TZ
n->ii->nn->CH3+C2H4CH3+C2H4->n
n->H+C3H6H+C3H6->ni->C3H6+HH+C3H6->i
k / k
QC
I//C
C/T
Z
Temperature (K)
0.5
0.6
0.7
0.8
0.9
1
1.1
400 600 800 1000 120014001600 18002000
QCISD(T)/CBS//CCSD(T)/ADZ
n->ii->nn->CH3+C2H4CH3+C2H4->n
n->H+C3H6H+C3H6->ni->C3H6+HH+C3H6->i
k / k
QC
I//C
C/T
Z
Temperature (K)
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Coupling of Uncertainties
J. Prager, H. N. Najm, J. Zador Proc. Comb. Inst. In press (2012) Paper 5D03
ΔE = ±1.0 kcal/mol Δν = 1.5 factor ν≠ = (50,850) cm-1
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Direct Sampling of Torsions
0.60.70.80.9
1
2
3
4
5
500 1000 1500 2000 2500
CH3OH + HO
2 -> CH
2OH + H
2O
2
MS-TST/SJK4D/SJK;B3S4D/SJK;B3S;w/Kin4D/SJK;B3S;w/vib4D/SJK;B3L;w/vib
k/k S
JK
Temperature (K)
0.80.9
1
2
3
0 500 1000 1500 2000
MS-T Entropy Test
1-butanoln-heptaneisoheptaneCH3OH+HO2
exp(
S calc
-Sex
pt)
Temperature (K)
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Pressure Dependence: Comparison with Expt
<ΔEdown> = 150 (T/300)0.85 cm-1 <ΔEdown> = 100 (T/300)0.85 cm-1
Propane Decomposition Acetaldehyde Decomposition
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C2H3 -> C2H2 + H
Delta Edown Fit 237 cm-1
Trajectory 470 cm-1
Energy Transfer Jasper & Oana AITSTME Pelzer, Miller, SJK
Experiment Knyazev & Slagle
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A Priori Predictions of Pressure Dependence
0.2
0.3
0.4
0.5
0.6
0.70.80.91
0.01 0.1 1 10 100
gamma=5gamma=6gamma=8
gamma=10gamma=15gamma=30
k/k_strong
P(bar)
Trajectory Simulations of Energy Transfer A Priori P(E’-> E) 1D Master Equation Assumes Strong Collider in J – Not Valid P(E’,J’->E,J) ΔEdown ΔJdown 2-Dimensional Master Equation (E,J)
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Coupling of Uncertainties: n-propyl + O2
C. F. Goldsmith, A. S. Tomlin, S. J. Klippenstein, Proc. Comb. Inst. 34, in press (2012) Paper 2D09
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Funding
US-Department Of Energy 1. Chemical-Physics Program – Chemical Dynamics
in the Gas Phase 2. Argonne-Sandia Consortium on High Pressure
Combustion Chemistry 3. Combustion Energy Frontier Research Center 4. An Expert Ab Initio Transition-State-Theory-Based
Master Equation Code