Ethanol Paper

A Detailed ChemicalKinetic Model for HighTemperature EthanolOxidationNICK M. MARINOV

Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550

Received 20 August 1998; accepted 15 October 1998

ABSTRACT: A detailed chemical kinetic model for ethanol oxidation has been developed andvalidated against a variety of experimental data sets. Laminar flame speed data (obtainedfrom a constant volume bomb and counterflow twin-flame), ignition delay data behind areflected shock wave, and ethanol oxidation product profiles from a jet-stirred and turbulentflow reactor were used in this computational study. Good agreement was found in modelingof the data sets obtained from the five different experimental systems. The computationalresults show that high temperature ethanol oxidation exhibits strong sensitivity to the fall-offkinetics of ethanol decomposition, branching ratio selection for C H OH 1 OH 4 Products,2 5

and reactions involving the hydroperoxyl (HO2) radical.The multichanneled ethanol decomposition process is analyzed by RRKM/Master Equation

theory, and the results are compared with those obtained from earlier studies. The ten-param-eter Troe form is used to define the rate expression asC H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

` 21.68 21k 5 5.94E23 T exp(245880 K/T) (s )o 218.9 3k 5 2.88E85 T exp(255317 K/T) (cm /mol/sec)

F 5 0.5 exp(2T/200 K) 1 0.5 exp(2T/890 K) 1 exp(24600 K/T)cent

and the rate expression asC H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

` 0.09 21k 5 2.79E13 T exp(233284 K/T) (s )o 218.85 3k 5 2.57E83 T exp(243509 K/T) (cm /mol/sec)

F 5 0.3 exp(2T/350 K) 1 0.7 exp(2T/800 K) 1 exp(23800 K/T)cent

with an applied energy transfer per collision value of 21,DE . 5 500 cm .down

An empirical branching ratio estimation procedure is presented which determines the tem-perature dependent branching ratios of the three distinct sites of hydrogen abstraction fromethanol. The calculated branching ratios for C H OH 1 OH, C H OH 1 O, C H OH 12 5 2 5 2 5

are compared to experimental data. q 1999 John Wiley & Sons, Inc.* Int JH, and C H OH 1 CH2 5 3

Chem Kinet 31: 183–220, 1999

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Correspondence to: N. M. MarinovContract grant Sponsor: U.S. Department of Energy/Lawrence

Livermore Natl. Lab.Contract grant number: W-7405-ENG-48

r1999 John Wiley & Sons, Inc. *This article is a U.S. governmentwork and, as such, is in the public domain in the United States ofAmerica. CCC 0538-8066/99/030183-38

INTRODUCTION

In recent years, considerable interest in ethanol as afuel extender, octane enhancer, oxygenate, and a neat

fuel has increased dramatically because of concernsassociated with conventional transportation fuels. Theelimination of tetra-ethyl lead in gasoline during themid-1980s and the 1990 Clean Air Act Amendmentshave required refinery operations to provide oxygen-ated gasoline in order to meet octane quality demandsand reduce carbon monoxide emissions and smog inthe nation’s most polluted areas. Currently, ethanoland methyl tert-butyl ether (MTBE) are the mostwidely used oxygenated fuels, and are most commonlyused in Federal and California reformulated gasolineand winter oxygenated gasoline in the Western UnitedStates. Ethanol may be considered as the preferred ox-ygenate since MTBE is a suspected carcinogen. Fur-thermore, ethanol possesses the advantage of beingproduced from renewable fuels like biomass whileMTBE requires isobutene, a waste fossil fuel productin the gasoline refining process, for synthesis, and eth-anol has roughly double the oxygen content thanMTBE on an oxygen to carbon basis. Recently, MTBEhas been reported as a drinking water contaminant inurban wells, aquifers, springs, and municipal waterreservoirs across the United States, especially in Cal-ifornia [1]. The potential removal of MTBE from re-formulated gasoline has greatly renewed interest inethanol as a gasoline additive.

There are fundamental and practical reasons for ex-amining the oxidation of ethanol. Approximately 6–10 vol % of reformulated gasoline may consist of eth-anol, as required by current federal and state urban airquality standards. As regulations on pollutant emis-sions become stricter, the amount of oxygenated fuellike ethanol in gasoline could increase. Therefore, weneed a full understanding of the reaciton pathways bywhich ethanol is oxidized and of the pollutant speciesthat it may produce. This understanding will allow in-dustry and regulatory agencies to better evaluate thefeasibility and relationship between the combustionprocess and pollutant emissions when using ethanol.

Previous detailed chemical kinetic modeling stud-ies performed during the early 1990s have greatly im-proved the level of understanding of the ethanol oxi-dation and pyrolysis process since the originalmodeling work of Natarajan and Bhaskaran [2]. Thesemodeling efforts focused on problems of ethanol ig-nition delay from shock tubes [2,3,4,7], ethanol lam-inar flame speeds in burners [4,7], and product profilesfrom ethanol pyrolysis and oxidation studies in static[5], turbulent flow [4,6], and jet-stirred reactors [7].Additional evidence of mechanistic features importantto describing ethanol reaction kinetics from static [8–11] and flow reactors [12–14], and information onautoignition characteristics in a rapid compression ma-chine [15] and combustion bomb [16], pressure, tem-

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perature, and mixture strength effects on flame prop-agation rates [17] or modes of formation of soot indiffusion flames [18,19] have proven to be useful forethanol model development. These experimentalworks have been previously summarized [6] and nofurther elaboration will be presented. The importantissues raised in the previous modeling works concernspecific features of the ethanol reaction kinetics, inparticular, the branching ratio assignments for the H-atom abstraction reactions from ethanol and the fall-off kinetics of the ethanol decomposition reactions.

The modeling studies of Borisov et al. [5] and Nor-ton and Dryer [6] were the first to address the issue ofthe three distinct H-atom sites in ethanol and the re-sulting temperature dependent product distributionduring its combustion. Their modeling studies showedgood agreement with the time history of the reactionproducts evolution during ethanol pyrolysis and oxi-dation. These results emphasized the importance ofdistinguishing the three C2H5O isomers that formthrough H-atom abstraction from ethanol, and thebranching ratio assignments for proper product deter-mination. However, these authors also noted that thenarrow temperature range of their experiments pre-vented the determination of the branching ratio depen-dence with temperature. These authors agree that ad-ditional work is needed to clarify the nature of thetemperature dependent behavior of the branching ra-tios for CH3CHOH,C H OH 1 X 4 {CH CH OH,2 5 2 2

O, H, CH3, HO2, etc.}.CH CH O} 1 XH {X 5 OH,3 2

The shock tube modeling work for ethanol hasshown contradictory findings, especially concerningthe nature of the pressure dependence involving the

decomposi-C H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

tion reaction and those reactions that exhibit the great-est sensitivity to ignition delay. The important chaininitiation step for shock tube conditions, C H OH2 5

, has been previously as-(1M) 4 CH 1 CH O(1M)3 2

sumed to exhibit second-order behavior in the re-flected shock ignition delay modeling study of Nata-rajan and Bhaskaran [2], and Dunphy and Simmie [3],or the reaction was shown to be in the fall-off, psuedo-first order region by Borisov et al. in reflected shockpyrolysis experiments. These studies were conductedat very similar conditions of pressure and temperature.Further complications were shown in the modelingand sensitivity analysis study of ethanol ignition de-lays by Dunphy and Simmie [3], Curran et al. [3,20],Egolfopoulos et al. [4], and Dagaut et al. [7]. Egol-fopoulos demonstrated good modeling agreement withthe Natarajan ignition delay data sets for equivalenceratios of 0.5–2.0, and found C H OH 4 CH 12 5 3

as the most sensitive reaction to ignition delayCH OH2

which agreed with the earlier finding of Natarajan.

However, Curran, Dagaut, and Dunphy found a lackof sensitivity for this chain initating ethanol decom-position reaction when modeling ignition delays fromreflected shocks of various mix-C H OH9O 9Ar2 5 2

ture strengths at conditions of 1100–1900 K and 2.0–4.5 bar. Curran showed the ethanol ignition delay tobe most sensitive to H 1 O 4 O 1 OH, H 12

O 1 M 4 HO 1 M, CH 1 HO 4 CH O 12 2 3 2 3

and H2 1 OH 4 H2O 1 H reactions. These sen-OH,sitivity analysis results were similar to the sensitivityanalysis findings of Dunphy and Dagaut. Also, theCurran modeling efforts suggested that ethanol de-composition occurs at or very near the high pressurelimit for the conditions of their study [20]. This par-ticular result differs from the earlier findings of Bori-sov et al. and the assumption made by Natarajan andDunphy.

The primary objective of the current study is topresent new rate constant expressions for ethanol de-composition and H-atom abstraction reactions fromethanol, as well as to develop and validate a detailedchemical kinetic model for ethanol oxidation by com-parison with experimental data sets obtained under avariety of high temperature conditions. The modelingstudy examined ignition delay data from shock tubes,laminar flame speed data from a combustion bomb anda counterflow twin flame, and species profiles fromethanol oxidation in jet-stirred and turbulent flow re-actors. The data sets considered span the temperaturerange of 1000–1700 K, a pressure range of 1.0–4.5atm, and an equivalence ratio range of 0.5–2.0. Thisobjective is to be achieved by an empirical branchingratio estimation procedure that determines the temper-ature dependent branching ratios of the three distinctsites of hydrogen abstraction from ethanol, fall-off rateconstant calculations for the multichanneled ethanoldecomposition process, and reaction pathway and sen-sitivity analysis. The latter approach is extensivelyused in order to help in the model refinement and toidentify those reactions and their accompanying rateconstants that exhibit a strong influence on the ethanoloxidation process. Hopefully, the results of this workwill lead to an improved level of understanding of thehigh temperature ethanol oxidation process.

DISCUSSION OF THE COMPUTATIONALMODELS

The modeling computations were performed using theCHEMKIN-II software [21] in conjunction with theSENKIN [22], PREMIX [23], and PSR [24] programs.The SENKIN program predicts the time-dependentchemical kinetics behavior of a homogeneous gas

phase mixture in a closed system. This particular pro-gram was used to calculate ignition delays in a shocktube, and to study fuel oxidation in a turbulent flowreactor. The ignition delay calculations were per-formed by assuming an adiabatic system and a con-stant density gas behind the reflected shock wave. Theflow reactor calculations were performed at constantpressure with the additional constraint of using the ex-perimentally measured temperature profile as sug-gested by Norton and Dryer [6]. The laminar flamespeed calculations were performed using the PREMIXcode for freely propagating flames. These computa-tions require the flame front to be one-dimensionalwith no heat loss to the surroundings. The central dif-ferencing technique was used in the numerical inte-gration of the laminar flame speeds at unburned gasconditions of 1.0 atm and 298 K. The upwind differ-encing scheme was used for calculations performed atpressures greater than 1.0 atm and unburned gas tem-peratures greater than 450 K. Two hundred zones andgreater were used in the upwind differencing integra-tions. Thermal diffusion was included in the adiabaticfreely propagating flame calculations. The PSR (per-fectly-stirred reactor) program was used to calculatethe species concentrations for the jet-stirred reactorstudy. The PSR code determines the steady-state spe-cies composition in the reactor per prescribed temper-ature. The PSR simulation requires the important as-sumption that the rate of conversion from reactants toproducts is controlled by the chemical reaction ratesand not by the mixing process. This assumption re-quires the mixing process to be infinitely fast, and asa consequence no spatial temperature and concentra-tion gradients are found in the stirred reactor.

The detailed chemical kinetic model was assembledusing reaction submechanisms developed previouslyfor hydrogen [25], methane [26], ethylene [27,28], eth-ane [26], and propane oxidation [29]. The hierarchicalnature of the model development for the C3 hydrocar-bon submechanism relied on using literature-based ki-netic data whenever possible, evaluated kinetic rateconstant information, theoretically calculated rate pa-rameters, and rate constant estimations based on anal-ogies to similar reactions. The compiled ethanol oxi-dation mechanism is listed in Table I and consists of56 species and 351 reversible reactions. Third bodyefficiencies and pressure corrections were applied asnecessary to the dissociation, recombination, and ad-dition reactions. These reactions are expressed in ei-ther the ten parameter Troe format or in the Linde-mann-Hinshelwood description for fall-off kinetics.

Transport properties were obtained from the SandiaCHEMKIN transport data base [30] as found in theTRANDAT file of the Sandia TRANFIT program.

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Transport properties for species not found in the da-tabase were estimated using the methods described byWang and Frenklach [31].

The thermodynamic properties for the species usedin this study were primarily obtained from the CHE-MKIN thermodynamic database [32], and Burcat andMcBride [33]. Thermodynamic properties for thosespecies not found in the databases were estimated bygroup additivity [34–36]. These estimated specificheats, standard state enthalpies, and standard state en-tropies data were fitted for the 300–1500 K range andextrapolated to 5000 K using the Harmonic OscillatorEquation and Exponential Function methods ofTHERM [36]. The THERM program generates thefourteen polynomial coefficients as used in the NASAComplex Equilibrium program [37]. The compiliationof the thermochemical data in polynomial coeffi-cient along with the reaction kinetics and transportmay be obtained by e-mail from the author ([email protected]). Table II shows the thermodynamicdata used in this study that is not presently found inthe Sandia CHEMKIN Thermodynamic database re-port [32].

DISCUSSION OF THE REACTIONKINETICS

Branching Ratios for H-Atom AbstractionReactions from Ethanol

The ethanol submechanism was developed by thor-oughly reviewing the kinetics literature for rate con-stants and branching ratios of elementary reactions in-volving C2H5OH, CH3CHOH, C2H4OH, CH3CH2O,and CH3HCO. The detailed chemical kinetic modeltreats all three distinct sites of hydrogen abstraction inthe ethanol molecule, and therefore the model consid-ers the subsequent reactions of all three isomers ofC2H5O (i.e., CH3CHOH, C2H4OH, and CH3CH2O).Currently, a very limited amount of direct branchingratio information exists for H-atom abstraction reac-tions involving ethanol. Direct measurements ofbranching ratios can be found for temperatures below600 K, and at 3500 K for [38,39],C H OH 1 OH2 5

[40,41], and [42] re-C H OH 1 O C H OH 1 CH2 5 2 5 3

actions. However, these data may not be applicable tothe conditions examined in the present study. Previousmodeling efforts have treated the branching ratios byeither (1) using a total overall rate constant for

(where, and CH3) andC H OH 1 X X 5 OH,O,H,2 5

partitioning the overall rate constant by temperatureindependent branching ratios for the various abstract-able H-atom sites [6], or (2) using rate constants from

analogous reactions that exhibit similar bond strengthsas found in ethanol without constraining the overallrate constant [20]. The success of the first approach isdependent on having a complete understanding of thecombustion chemistry of ethanol and its reaction in-termediates. The second approach fails to enforce theoverall rate constant, andC H OH 1 X 4 Products2 5

assumes the correct temperature dependent branchingratios would fall out from the analogous abstractionrate constants in and as as-C H 1 X CH OH 1 X3 8 3

signed to . In this study, it is expectedC H OH 1 X2 5

that the branching ratios will exhibit temperature de-pendence, and that a simple methodology would haveto be adopted in order to extrapolate the measured lowtemperature branching ratios to high temperature con-ditions or to make predictions in absence of directbranching ratio measurements. The following ap-proach was adopted which uses previously determinedbranching ratio values from model compounds that ex-hibit similar structural and chemical bonding charac-teristics as those found in ethanol. Propane and meth-anol were used as the model compounds to treat therelative branching ratios for the three specific H-atomabstraction sites in ethanol. This was done as ampleexperimental and theoretical information exists at el-evated temperatures on the relative rates of H-atomabstraction from these species.

Propane and methanol have very similar O9H andC9H bond strengths as found in ethanol. This isshown in Figure 1. The similarity in bond strengths andstructural characteristics between the model compoundsand ethanol allows for a set of equations to be devel-oped and solved. The relative rates of H-atom abstrac-

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Figure 1 The bond strengths of the various abstractable H-atoms from ethanol, propane, and methanol.

Table I Reaction Mechanism Rate Coefficients Units are Moles, cm3, Seconds, K, andb(k 5 A T exp(2E /RT),f a

Calories/Mole)

Reaction A b Ea Reference

HYDROGEN–OXYGEN SUBMECHANISM1. OH 1 H 5 H 1 H O2 2 2.14E 1 08 1.52 3449.0 [25]2. O 1 OH 5 O 1 H2 2.02E 1 14 20.4 0.0 [25]3. O 1 H 5 OH 1 H2 5.06E 1 04 2.67 6290.0 [25]4. aH 1 O (1M) 5 HO (1M)2 2 4.52E 1 13 0.0 0.0 [25]

Low pressure limit:Enhanced Third Body Efficiencies:H O 5 0.0, H 5 0.0, N 5 0.0, CH 5 10.0,2 2 2 4

CO 5 3.8, CO 5 1.92

1.05E 1 19 21.257 0.0

4a. H 1 O (1N ) 5 HO (1N )2 2 2 2 4.52E 1 13 0.0 0.0 [25]Low pressure limit: 2.03E 1 20 21.59 0.0

4b. H 1 O (1H ) 5 HO (1H )2 2 2 2 4.52E 1 13 0.0 0.0 [25]Low pressure limit: 1.52E 1 19 21.133 0.0

4c. H 1 O (1H O) 5 HO (1H O)2 2 2 2 4.52E 1 13 0.0 0.0 [25]Low pressure limit: 2.10E 1 23 22.437 0.0

5. OH 1 HO 5 H O 1 O2 2 2 2.13E 1 28 24.827 3500.0 [26]Duplicate reaction

OH 1 HO 5 H O 1 O2 2 2 9.10E 1 14 0.0 10964.Duplicate reaction

6. H 1 HO 5 OH 1 OH2 1.50E 1 14 0.0 1000.0 [25]7. H 1 HO 5 H 1 O2 2 2 6.63E 1 13 0.0 2126.0 [65]8. H 1 HO 5 O 1 H O2 2 3.01E 1 13 0.0 1721.0 [25]9. O 1 HO 5 O 1 OH2 2 3.25E 1 13 0.0 0.0 [25]

10. 2OH 5 O 1 H O2 3.57E 1 04 2.4 22112.0 [25]11. H 1 H 1 M 5 H 1 M2 1.00E 1 18 21.0 0.0 [25]

Enhanced Third Body Efficiencies:H O 5 0.0, H 5 0.02 2

11a. H 1 H 1 H 5 H 1 H2 2 2 9.20E 1 16 20.6 0.0 [25]11b. H 1 H 1 H O 5 H 1 H O2 2 2 6.00E 1 19 21.25 0.0 [25]12. H 1 OH 1 M 5 H O 1 M2 2.21E 1 22 22.0 0.0 [25]

Enhanced Third Body Efficiencies:H O 5 6.42

13. H 1 O 1 M 5 OH 1 M 4.71E 1 18 21.0 0.0 [25]H O 5 6.42

14. O 1 O 1 M 5 O 1 M2 1.89E 1 13 0.0 21788.0 [25]15. HO 1 HO 5 H O 1 O2 2 2 2 2 4.20E 1 14 0.0 11982.0 [25]

Duplicate reactionHO 1 HO 5 H O 1 O2 2 2 2 2 1.30E 1 11 0.0 21629.0

Duplicate reaction16. bOH 1 OH(1M) 5 H O (1M)2 2 1.24E 1 14 20.37 0.0 [25]

Low pressure limit: 3.04E 1 30 24.63 2049.0 [25]Troe Parameters: a 5 0.470, T*** 5 100.0,T* 5 2000.0T** 5 1.0E 1 15

17. H O 1 H 5 HO 1 H2 2 2 2 1.98E 1 06 2.0 2435.0 [25]18. H O 1 H 5 OH 1 H O2 2 2 3.07E 1 13 0.0 4217.0 [25]19. H O 1 O 5 OH 1 HO2 2 2 9.55E 1 06 2.0 3970.0 [25]20. H O 1 OH 5 H O 1 HO2 2 2 2 2.40E 1 00 4.042 22162.0 [25]

C1 HYDROCARBON SUBMECHANISM21. CH 1 CH (1M) 5 C H (1M)3 3 2 6 9.22E 1 16 21.174 636.0 [26]

Low pressure limit: 1.14E 1 36 25.246 1705.0 [26]Troe Parameters: a 5 0.405, T*** 5 1120.0,T* 5 69.6, T** 5 1.0E 1 15Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

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Table I (Continued)


22. CH 1 H(1M) 5 CH (1M)3 4 2.14E 1 15 20.4 0.0 [26]Low pressure limit: 3.31E 1 30 24.0 2108.0Troe Parameters: a 5 0.0, T*** 5 1.0E 2 15,T* 5 1.0E 2 15, T** 5 40.Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

23. CH 1 H 5 CH 1 H4 3 2 2.20E 1 04 3.0 8750.0 [26]24. CH 1 OH 5 CH 1 H O4 3 2 4.19E 1 06 2.0 2547.0 [26]25. CH 1 O 5 CH 1 OH4 3 6.92E 1 08 1.56 8485.0 [26]26. CH 1 HO 5 CH 1 H O4 2 3 2 2 1.12E 1 13 0.0 24640.0 [26]27. CH 1 HO 5 CH O 1 OH3 2 3 7.00E 1 12 0.0 0.0 [26]28. CH 1 HO 5 CH 1 O3 2 4 2 3.00E 1 12 0.0 0.0 [26]29. CH 1 O 5 CH O 1 H3 2 8.00E 1 13 0.0 0.0 [26]30. CH 1 O 5 CH O 1 O3 2 3 1.45E 1 13 0.0 29209.0 [26]31. CH 1 O 5 CH O 1 OH3 2 2 2.51E 1 11 0.0 14640.0 [26]32. CH O 1 H 5 CH 1 OH3 3 1.00E 1 13 0.0 0.0 (a)33. CH OH 1 H 5 CH 1 OH2 3 1.00E 1 13 0.0 0.0 (a)34. CH 1 OH 5 CH (s) 1 H O3 2 2 2.00E 1 13 0.0 550.0 [66]35. CH 1 OH 5 CH 1 H O3 2 2 3.00E 1 06 2.0 2500.0 [26]36. CH 1 OH 5 HCOH 1 H3 2 1.00E 1 10 0.0 2415.0 [66]37. CH 1 H 5 CH 1 H3 2 2 9.00E 1 13 0.0 15100.0 [26]38. CH 1 M 5 CH 1 H 1 M3 2 6.90E 1 14 0.0 82469.0 [26]39. CH 1 M 5 CH 1 H 1 M3 2 1.90E 1 16 0.0 91411.0 [26]40. CH 1 OH(1M) 5 CH OH(1M)3 3 8.70E 1 13 0.1 0.0 [26]

Low pressure limit: 5.75E 1 41 27.4 626.0Troe Parameters: a 5 0.025, T*** 5 1.0E 2 15,T* 5 8000.0, T** 5 3000.0Enhanced Third Body Efficiencies:H O 5 10.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

41. CH OH(1M) 5 CH (s) 1 H O(1M)3 2 2 2.84E 1 10 1.00 83871.0 (b,c)Low pressure limit: 1.78E 1 49 28.81 93369.0Troe Parameters: a 5 0.90, T*** 5 740.,T* 5 980., T** 5 5100.Enhanced Third Body Efficiencies:H O 5 10.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

42. CH OH(1M) 5 HCOH 1 H (1M)3 2 4.20E 1 09 1.12 85604.0 (b,c)Low pressure limit: 5.02E 1 47 28.40 94823.0Troe Parameters: a 5 0.9, T*** 5 615.,T* 5 915., T** 5 4615.Enhanced Third Body Efficiencies:H O 5 10.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

43. CH OH(1M) 5 CH O 1 H (1M)3 2 2 2.03E 1 09 1.00 91443.0 (b,c)Low pressure limit: 9.78E 1 47 28.40 101761.0Troe Parameters: a 5 0.9, T*** 5 825.,T* 5 1125., T** 5 5700.Enhanced Third Body Efficiencies:H O 5 10.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

44. CH OH 1 OH 5 CH OH 1 H O3 2 2 2.61E 1 05 2.182 21344.0 [26]45. CH OH 1 OH 5 CH O 1 H O3 3 2 2.62E 1 06 2.056 916.0 [26]46. CH OH 1 O 5 CH OH 1 OH3 2 3.88E 1 05 2.5 3080.0 [26]47. CH OH 1 H 5 CH OH 1 H3 2 2 1.70E 1 07 2.1 4868.0 [26]48. CH OH 1 H 5 CH O 1 H3 3 2 4.24E 1 06 2.1 4868.0 [26]49. CH OH 1 CH 5 CH OH 1 CH3 3 2 4 3.19E 1 01 3.17 7171.0 [26]

(Continued)

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Table I (Continued)


50. CH OH 1 CH 5 CH O 1 CH3 3 3 4 1.45E 1 01 3.10 6935.0 [26]51. CH OH 1 HO 5 CH OH 1 H O3 2 2 2 2 9.64E 1 10 0.0 12578.0 [26]52. CH O 1 H(1M) 5 CH O(1M)2 3 5.40E 1 11 0.454 2600.0 [67]

Low pressure limit: 1.50E 1 30 24.80 5560.0Troe Parameters: a 5 0.758, T*** 5 94.,T* 5 1555., T** 5 4200.Enhanced Third Body Efficiencies: H O 5 5.02

53. CH O 1 H(1M) 5 CH OH(1M)2 2 5.40E 1 11 0.454 3600.0 [67]Low pressure limit: 9.10E 1 31 24.82 6530.0Troe Parameters: a 5 0.719, T*** 5 103.,T* 5 1291., T** 5 4160.Enhanced Third Body Efficiencies: H O 5 5.02

54. CH O 1 CH 5 CH O 1 CH3 3 2 4 1.20E 1 13 0.0 0.0 [67]55. CH O 1 H 5 CH O 1 H3 2 2 2.00E 1 13 0.0 0.0 [26]56. CH OH 1 H 5 CH O 1 H2 2 2 2.00E 1 13 0.0 0.0 [26]57. CH O 1 OH 5 CH O 1 H O3 2 2 1.00E 1 13 0.0 0.0 [26]58. CH OH 1 OH 5 CH O 1 H O2 2 2 1.00E 1 13 0.0 0.0 [26]59. CH O 1 O 5 CH O 1 OH3 2 1.00E 1 13 0.0 0.0 [26]60. CH OH 1 O 5 CH O 1 OH2 2 1.00E 1 13 0.0 0.0 [26]61. CH O 1 O 5 CH O 1 HO3 2 2 2 6.30E 1 10 0.0 2600.0 [26]62. CH OH 1 O 5 CH O 1 HO2 2 2 2 1.57E 1 15 21.0 0.0 [26]

Duplicate reactionCH OH 1 O 5 CH O 1 HO2 2 2 2 7.23E 1 13 0.0 3577.0

Duplicate reaction63. HCOH 1 OH 5 HCO 1 H O2 2.00E 1 13 0.0 0.0 [26]64. HCOH 1 H 5 CH O 1 H2 2.00E 1 14 0.0 0.0 [26]65. HCOH 1 O 5 CO 1 OH 1 H 8.00E 1 13 0.0 0.0 [26]66. HCOH 1 O 5 CO 1 OH 1 OH2 1.00E 1 13 0.0 0.0 [26]67. HCOH 1 O 5 CO 1 H O2 2 2 1.00E 1 13 0.0 0.0 [26]68. HCOH 5 CH O2 2.10E 1 19 23.07 31700.0 [68](d)69. CH 1 H 5 CH 1 H2 2 1.00E 1 18 21.56 0.0 [26]70. CH 1 OH 5 CH 1 H O2 2 1.13E 1 07 2.0 3000.0 [26]71. CH 1 OH 5 CH O 1 H2 2 2.50E 1 13 0.0 0.0 [26]72. CH 1 CO 5 CH O 1 CO2 2 2 1.10E 1 11 0.0 1000.0 [26]73. CH 1 O 5 CO 1 H 1 H2 5.00E 1 13 0.0 0.0 [26]74. CH 1 O 5 CO 1 H2 2 3.00E 1 13 0.0 0.0 [26]75. CH 1 O 5 CH O 1 O2 2 2 3.29E 1 21 23.3 2868.0 [26]76. CH 1 O 5 CO 1 H 1 H2 2 2 3.29E 1 21 23.3 2868.0 [26]77. CH 1 O 5 CO 1 H2 2 2 2 1.01E 1 21 23.3 1508.0 [26]78. CH 1 O 5 CO 1 H O2 2 2 7.28E 1 19 22.54 1809.0 [26]79. CH 1 O 5 HCO 1 OH2 2 1.29E 1 20 23.3 284.0 [26]80. CH 1 CH 5 C H 1 H2 3 2 4 4.00E 1 13 0.0 0.0 [26]81. CH 1 CH 5 C H 1 H 1 H2 2 2 2 4.00E 1 13 0.0 0.0 [26]82. CH 1 HCCO 5 C H 1 CO2 2 3 3.00E 1 13 0.0 0.0 [26]83. CH 1 C H 5 H CCCH 1 H2 2 2 2 1.20E 1 13 0.0 6600.0 [26]84. ‡CH (s) 1 M 5 CH 1 M2 2 1.00E 1 13 0.0 0.0 [26]

Enhanced Third Body Efficiencies:H 5 12.0, C H 5 4.0, H O 5 3.02 2 2

85. CH (s) 1 CH 5 CH 1 CH2 4 3 3 4.00E 1 13 0.0 0.0 [26]86. CH (s) 1 C H 5 CH 1 C H2 2 6 3 2 5 1.20E 1 14 0.0 0.0 [26]87. CH (s) 1 O 5 CO 1 OH 1 H2 2 7.00E 1 13 0.0 0.0 [26]88. CH (s) 1 H 5 CH 1 H2 2 3 7.00E 1 13 0.0 0.0 [26]89. CH (s) 1 C H 5 H CCCH 1 H2 2 2 2 1.50E 1 14 0.0 0.0 [26]

(Continued)



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Table I (Continued)


90. CH (s) 1 C H 5 AC H 1 H2 2 4 3 5 1.30E 1 14 0.0 0.0 [26]91. CH (s) 1 O 5 CO 1 H 1 H2 3.00E 1 13 0.0 0.0 [26]92. CH (s) 1 OH 5 CH O 1 H2 2 3.00E 1 13 0.0 0.0 [26]93. CH (s) 1 H 5 CH 1 H2 2 3.00E 1 13 0.0 0.0 [26]94. CH (s) 1 CO 5 CH O 1 CO2 2 2 3.00E 1 12 0.0 0.0 [26]95. CH (s) 1 CH 5 C H 1 H2 3 2 4 2.00E 1 13 0.0 0.0 [26]96. CH (s) 1 CH CO 5 C H 1 CO2 2 2 4 1.60E 1 14 0.0 0.0 [26]97. CH 1 O 5 HCO 1 O2 3.30E 1 13 0.0 0.0 [26]98. CH 1 O 5 CO 1 H 5.70E 1 13 0.0 0.0 [26]99. CH 1 OH 5 HCO 1 H 3.00E 1 13 0.0 0.0 [26]

100. CH 1 CO 5 HCO 1 CO2 3.40E 1 12 0.0 690.0 [26]101. CH 1 H O 5 CH O 1 H2 2 1.17E 1 15 20.75 0.0 [26]102. CH 1 CH O 5 CH CO 1 H2 2 9.46E 1 13 0.0 2515.0 [26]103. CH 1 C H 5 C H 1 H2 2 3 2 1.00E 1 14 0.0 0.0 [26]104. CH 1 CH 5 C H 1 H2 2 2 4.00E 1 13 0.0 0.0 [26]105. CH 1 CH 5 C H 1 H3 2 3 3.00E 1 13 0.0 0.0 [26]106. CH 1 CH 5 C H 1 H4 2 4 6.00E 1 13 0.0 0.0 [26]107. CH O 1 OH 5 HCO 1 H O2 2 3.43E 1 09 1.18 2447.0 [26]108. CH O 1 H 5 HCO 1 H2 2 2.19E 1 08 1.77 3000.0 [26]109. CH O 1 M 5 HCO 1 H 1 M2 3.31E 1 16 0.0 81000.0 [26]110. CH O 1 O 5 HCO 1 OH2 1.80E 1 13 0.0 3080.0 [26]111. HCO 1 O 5 HO 1 CO2 2 7.58E 1 12 0.0 410.0 [26]112. HCO 1 M 5 H 1 CO 1 M 1.86E 1 17 21.0 17000.0 [26]

Enhanced Third Body Efficiencies:H2O 5 5.0, H2 5 1.87, CO2 5 3.0, CO 5 1.87,CH4 5 2.81

113. HCO 1 OH 5 H O 1 CO2 1.00E 1 14 0.0 0.0 [26]114. HCO 1 H 5 CO 1 H2 1.19E 1 13 0.25 0.0 [26]115. HCO 1 O 5 CO 1 OH 3.00E 1 13 0.0 0.0 [26]116. HCO 1 O 5 CO 1 H2 3.00E 1 13 0.0 0.0 [26]117. HCOOH 1 M 5 CO 1 H O 1 M2 2.09E 1 14 0.0 40400.0 [69]118. HCOOH 1 M 5 CO 1 H 1 M2 2 1.35E 1 15 0.0 60600.0 [69]119. HCOOH 1 OH 5 CO 1 H O 1 H2 2 2.62E 1 06 2.056 916.0 (e)120. HCOOH 1 OH 5 CO 1 H O 1 OH2 1.85E 1 07 1.50 2962.0 (f)121. HCOOH 1 H 5 CO 1 H 1 H2 2 4.24E 1 06 2.10 4868.0 (e)122. HCOOH 1 H 5 CO 1 H 1 OH2 6.06E 1 13 20.35 2988.0 (f)123. HCOOH 1 CH 5 CH 1 CO 1 OH3 4 3.90E 2 07 5.80 2200.0 (f)124. HCOOH 1 HO 5 CO 1 H O 1 OH2 2 2 2.40E 1 19 22.20 14030.0 (f)125. HCOOH 1 O 5 CO 1 OH 1 OH 1.77E 1 18 21.90 2975.0 (f)126. CO 1 OH 5 CO 1 H2 9.42E 1 03 2.25 22351.0 [26]127. CO 1 O 1 M 5 CO 1 M2 6.17E 1 14 0.0 3000.0 [26]128. CO 1 O 5 CO 1 O2 2 2.53E 1 12 0.0 47688.0 [26]129. CO 1 HO 5 CO 1 OH2 2 5.80E 1 13 0.0 22934.0 [26]

C2 HYDROCARBON SUBMECHANISM130. C H OH(1M) 5 CH OH 1 CH (1M)2 5 2 3 5.94E 1 23 21.68 91163.0 This Study

Low pressure limit: 2.88E 1 85 218.9 109914.0 (g)Troe Parameters: a 5 0.50, T*** 5 200.,T* 5 890.0, T** 5 4600.0Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

(Continued)

190 MARINOV


shortstandardlong

Table I (Continued)


131. C H OH(1M) 5 C H 1 OH(1M)2 5 2 5 1.25E 1 23 21.54 96005.0 This StudyLow pressure limit: 3.25E 1 85 218.81 114930.0 (g)Troe Parameters: a 5 0.50, T*** 5 300.,T* 5 900., T** 5 5000.Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

132. C H OH(1M) 5 C H 1 H O(1M)2 5 2 4 2 2.79E 1 13 0.09 66136.0 This StudyLow pressure limit: 2.57E 1 83 218.85 86452.0 (g)Troe Parameters: a 5 0.70, T*** 5 350.,T* 5 800., T** 5 3800.Enhanced Third Body Efficiencies:H O 5 5.02

133. C H OH(1M) 5 CH HCO 1 H (1M)2 5 3 2 7.24E 1 11 0.095 91007.0 This StudyLow pressure limit: 4.46E 1 87 219.42 115586.0 (g)Troe Parameters: a 5 0.90, T*** 5 900.,T* 5 1100., T** 5 3500.Enhanced Third Body Efficiencies:H O 5 5.02

134. C H OH 1 OH 5 C H OH 1 H O2 5 2 4 2 1.74E 1 11 0.27 600.0 This Study (h)135. C H OH 1 OH 5 CH CHOH 1 H O2 5 3 2 4.64E 1 11 0.15 0.0 This Study136. C H OH 1 OH 5 CH CH O 1 H O2 5 3 2 2 7.46E 1 11 0.30 1634.0 This Study137. C H OH 1 H 5 C H OH 1 H2 5 2 4 2 1.23E 1 07 1.80 5098.0 This Study (i)138. C H OH 1 H 5 CH CHOH 1 H2 5 3 2 2.58E 1 07 1.65 2827.0 This Study139. C H OH 1 H 5 CH CH O 1 H2 5 3 2 2 1.50E 1 07 1.60 3038.0 This Study140. C H OH 1 O 5 C H OH 1 H O2 5 2 4 2 9.41E 1 07 1.70 5459.0 This Study (j)141. C H OH 1 O 5 CH CHOH 1 H O2 5 3 2 1.88E 1 07 1.85 1824.0 This Study142. C H OH 1 O 5 CH CH O 1 H O2 5 3 2 2 1.58E 1 07 2.00 4448.0 This Study143. C H OH 1 CH 5 C H OH 1 CH2 5 3 2 4 4 2.19E 1 02 3.18 9622.0 This Study (k)144. C H OH 1 CH 5 CH CHOH 1 CH2 5 3 3 4 7.28E 1 02 2.99 7948.0 This Study145. C H OH 1 CH 5 CH CH O 1 CH2 5 3 3 2 4 1.45E 1 02 2.99 7649.0 This Study146. C H OH 1 HO 5 C H OH 1 H O2 5 2 2 4 2 2 1.23E 1 04 2.55 15750.0 This Study147. C H OH 1 HO 5 CH CHOH 1 H O2 5 2 3 2 2 8.20E 1 03 2.55 10750.0 This Study148. C H OH 1 HO 5 CH CH O 1 H O2 5 2 3 2 2 2 2.50E 1 12 0.00 24000.0 This Study149. CH CH O 1 M 5 CH HCO 1 H 1 M3 2 3 1.16E 1 35 25.89 25274.0 QRRK, 1 atm150. CH CH O 1 M 5 CH 1 CH O 1 M3 2 3 2 1.35E 1 38 26.96 23800.0 QRRK, 1 atm151. CH CH O 1 CO 5 C H 1 CO3 2 2 5 2 4.68E 1 02 3.16 5380.0 (l)152. CH CH O 1 O 5 CH HCO 1 HO3 2 2 3 2 4.00E 1 10 0.00 1100.0 [70]153. CH CH O 1 H 5 CH 1 CH OH3 2 3 2 3.00E 1 13 0.00 0.0 (a)154. CH CH O 1 H 5 C H 1 H O3 2 2 4 2 3.00E 1 13 0.00 0.0 (a)155. CH CH O 1 OH 5 CH HCO 1 H O3 2 3 2 1.00E 1 13 0.00 0.0 (a)156. CH CHOH 1 O 5 CH HCO 1 HO3 2 3 2 4.82E 1 14 0.00 5017.0 (m)

DuplicateCH CHOH 1 O 5 CH HCO 1 HO3 2 3 2 8.43E 1 15 21.20 0.0Duplicate

157. CH CHOH 1 CH 5 C H 1 H O3 3 3 6 2 2.00E 1 13 0.00 0.0 (a)158. CH CHOH 1 O 5 CH HCO 1 OH3 3 1.00E 1 14 0.00 0.0 (a)159. CH CHOH 1 H 5 CH 1 CH OH3 3 2 3.00E 1 13 0.00 0.0 (a)160. CH CHOH 1 H 5 C H 1 H O3 2 4 2 3.00E 1 13 0.00 0.0 (a)161. CH CHOH 1 HO 5 CH HCO 1 OH 1 OH3 2 3 4.00E 1 13 0.00 0.0 (a)162. CH CHOH 1 OH 5 CH HCO 1 H O3 3 2 5.00E 1 12 0.00 0.0 (a)163. CH CHOH 1 M 5 CH HCO 1 H 1 M3 3 1.00E 1 14 0.00 25000.0 (a)164. CH HCO 1 OH 5 CH CO 1 H O3 3 2 9.24E 1 06 1.50 2962.0 [71]165. CH HCO 1 OH 5 CH HCO 1 H O3 2 2 1.72E 1 05 2.40 815.0 [71]

(Continued)



shortstandardlong

Table I (Continued)


166. CH HCO 1 OH 5 CH 1 HCOOH3 3 3.00E 1 15 21.076 0.0 [71]167. CH HCO 1 O 5 CH CO 1 OH3 3 1.77E 1 18 21.90 2975.0 (o,p)168. CH HCO 1 O 5 CH HCO 1 OH3 2 3.72E 1 13 20.20 3556.0 (o,p)169. CH HCO 1 H 5 CH CO 1 H3 3 2 4.66E 1 13 20.35 2988.0 (o,q)170. CH HCO 1 H 5 CH HCO 1 H3 2 2 1.85E 1 12 0.40 5359.0 (o,q)171. CH HCO 1 CH 5 CH CO 1 CH3 3 3 4 3.90E 2 07 5.80 2200.0 (o,r)172. CH HCO 1 CH 5 CH HCO 1 CH3 3 2 4 2.45E 1 01 3.15 5727.0 (o,r)173. CH HCO 1 HO 5 CH CO 1 H O3 2 3 2 2 2.40E 1 19 22.20 14030.0 (o,s)174. CH HCO 1 HO 5 CH HCO 1 H O3 2 2 2 2 2.32E 1 11 0.40 14864.0 (o,s)175. CH HCO 1 O 5 CH CO 1 HO3 2 3 2 1.00E 1 14 0.0 42200.0 (a)176. CH HCO 1 H 5 CH 1 HCO2 3 5.00E 1 13 0.0 0.0 (a)177. CH HCO 1 H 5 CH CO 1 H2 2 2 2.00E 1 13 0.0 0.0 (a)178. CH HCO 1 O 5 CH O 1 HCO2 2 1.00E 1 14 0.0 0.0 [26]179. CH HCO 1 OH 5 CH CO 1 H O2 2 2 3.00E 1 13 0.0 0.0 [26]180. CH HCO 1 O 5 CH O 1 CO 1 OH2 2 2 3.00E 1 10 0.0 0.0 [26]181. CH CHO 1 CH 5 C H 1 CO 1 H2 3 2 5 4.90E 1 14 20.50 0.0 [26]182. CH CHO 1 HO 5 CH O 1 HCO 1 OH2 2 2 7.00E 1 12 0.00 0.0 (t)183. CH CHO 1 HO 5 CH HCO 1 O2 2 3 2 3.00E 1 12 0.00 0.0 (u)184. CH HCO 5 CH 1 CO2 3 1.17E 1 43 29.83 43756.0 QRRK, 1 atm185. CH HCO 5 CH CO 1 H2 2 1.81E 1 43 29.61 45868.0 QRRK, 1 atm186. C H 1 CH 5 C H 1 CH2 6 3 2 5 4 5.50E 2 01 4.0 8300.0 [26]187. C H 1 H 5 C H 1 H2 6 2 5 2 5.40E 1 02 3.5 5210.0 [26]188. C H 1 O 5 C H 1 OH2 6 2 5 3.00E 1 07 2.0 5115.0 [26]189. C H 1 OH 5 C H 1 H O2 6 2 5 2 7.23E 1 06 2.0 864.0 [26]190. C H 1 H 5 C H 1 H2 5 2 4 2 1.25E 1 14 0.0 8000.0 [26]191. C H 1 H 5 CH 1 CH2 5 3 3 3.00E 1 13 0.0 0.0 [26]192. C H 1 H 5 C H2 5 2 6 3.00E 1 13 0.0 0.0 [26]193. C H 1 OH 5 C H 1 H O2 5 2 4 2 4.00E 1 13 0.0 0.0 [26]194. C H 1 O 5 CH 1 CH O2 5 3 2 1.00E 1 14 0.0 0.0 [26]195. C H 1 HO 5 C H 1 O2 5 2 2 6 2 3.00E 1 12 0.0 0.0 [26]196. C H 1 HO 5 CH 1 CH O 1 OH2 5 2 3 2 3.00E 1 13 0.0 0.0 [26]197. C H 1 O 5 C H 1 HO2 5 2 2 4 2 2.89E 1 28 25.40 7585.0 [72]198. C H 1 O 5 CH HCO 1 OH2 5 2 3 4.90E 1 11 20.48 8357.0 [72]199. C H 1 OH 5 C H OH2 4 2 4 1.29E 1 12 0.0 2817.0 [73]200. C H OH 1 O 5 HOC H O2 4 2 2 4 2 1.00E 1 12 0.0 21100.0 (a)201. HOC H O 5 CH O 1 CH O 1 OH2 4 2 2 2 6.00E 1 10 0.0 24500.0 (a)202. C H 1 H 5 C H 1 H2 4 2 3 2 3.36E 2 07 6.0 1692.0 [26]203. C H 1 OH 5 C H 1 H O2 4 2 3 2 2.02E 1 13 0.0 5936.0 [26]204. C H 1 O 5 CH 1 HCO2 4 3 1.02E 1 07 1.88 179.0 [26]205. C H 1 O 5 CH HCO 1 H2 4 2 3.39E 1 06 1.88 179.0 [26]206. C H 1 CH 5 C H 1 CH2 4 3 2 3 4 6.62E 1 00 3.70 9500.0 [26]207. C H 1 H(1M) 5 C H (1M)2 4 2 5 1.08E 1 12 0.454 1822.0 [26]

Low pressure limit: 1.11E 1 34 25.00 4448.0Troe Parameters: a 5 1.0, T*** 5 1.0E 2 15,T* 5 95.0, T** 5 200.0Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

208. C H (1M) 5 C H 1 H (1M)2 4 2 2 2 1.80E 1 14 0.0 87000.0 [29]Low pressure limit: 1.50E 1 15 20.0 55443.0

209. C H 1 H(1M) 5 C H (1M)2 3 2 4 6.10E 1 12 0.27 280.0 [29]Low pressure limit: 9.80E 1 29 23.86 3320.0Troe Parameters: a 5 0.782, T*** 5 208.,T* 5 2663., T** 5 6095.Enhanced Third Body Efficiencies: H O 5 5.02

(Continued)

192 MARINOV


shortstandardlong

Table I (Continued)


210. C H 1 H 5 C H 1 H2 3 2 2 2 9.00E 1 13 0.0 0.0 [65]211. C H 1 O 5 CH CO 1 H2 3 2 3.00E 1 13 0.0 0.0 [26]212. C H 1 O 5 CH O 1 HCO2 3 2 2 1.70E 1 29 25.312 6500.0 [26]213. C H 1 O 5 CH HCO 1 O2 3 2 2 5.50E 1 14 20.611 5260.0 [26]214. C H 1 O 5 C H 1 HO2 3 2 2 2 2 2.12E 2 06 6.00 9484.0 [26]215. C H 1 OH 5 C H 1 H O2 3 2 2 2 2.00E 1 13 0.0 0.0 [26]216. C H 1 C H 5 C H 1 C H2 3 2 2 2 2 2 3.00E 1 13 0.0 0.0 [26]217. C H 1 CH 5 CH 1 C H2 3 2 2 2 5.00E 1 13 0.0 0.0 [26]218. ‡C H 1 CH 5 AC H 1 H2 3 3 3 5 4.73E 1 02 3.7 5677.0 [26]219. C H 1 CH 5 C H2 3 3 3 6 4.46E 1 56 213.0 13865.0 [26]220. C H 1 CH 5 C H 1 CH2 3 3 2 2 4 2.00E 1 13 0.0 0.0 [26]221. C H 1 OH 5 C H 1 H O2 2 2 2 3.37E 1 07 2.0 14000.0 [26]222. C H 1 OH 5 HCCOH 1 H2 2 5.04E 1 05 2.3 13500.0 [26]223. C H 1 OH 5 CH CO 1 H2 2 2 2.18E 2 04 4.5 21000.0 [26]

Duplicate reactionC H 1 OH 5 CH CO 1 H2 2 2 2.00E 1 11 0.0 0.0 [26]Duplicate reaction

224. C H 1 OH 5 CH 1 CO2 2 3 4.83E 2 04 4.0 22000.0 [26]225. HCCOH 1 H 5 CH CO 1 H2 1.00E 1 13 0.0 0.0 [26]226. C H 1 O 5 CH 1 CO2 2 2 6.12E 1 06 2.0 1900.0 [26]227. C H 1 O 5 HCCO 1 H2 2 1.43E 1 07 2.0 1900.0 [26]228. C H 1 O 5 C H 1 OH2 2 2 3.16E 1 15 20.6 15000.0 [26]229. C H 1 CH 5 C H 1 CH2 2 3 2 4 1.81E 1 11 0.0 17289.0 [26]230. C H 1 O 5 HCCO 1 OH2 2 2 4.00E 1 07 1.5 30100.0 [26]231. C H 1 M 5 C H 1 H 1 M2 2 2 4.20E 1 16 0.0 107000.0 [26]232. C H 1 H(1M) 5 C H (1M)2 2 2 3 3.11E 1 11 0.58 2589.0 [26]

Low pressure limit: 2.25E 1 40 27.269 6577.0 [26]Troe Parameters: a 5 1.0, T*** 5 1.0E 2 15,T* 5 675.0, T** 5 1.0E 1 15Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

233. CHOCHO(1M) 5 CH O 1 CO(1M)2 4.27E 1 12 0.0 50600.0 [26]Low pressure limit: 8.91E 1 16 0.0 49200.0 [26]

234. CHOCHO 5 CO 1 CO 1 H2 4.07E 1 42 28.5 69278.0 [26]235. CHOCHO 1 OH 5 HCO 1 CO 1 H O2 1.00E 1 13 0.0 0.0 [26]236. CHOCHO 1 O 5 HCO 1 CO 1 OH 7.24E 1 12 0.0 1970.0 [26]237. CHOCHO 1 H 5 CH O 1 HCO2 1.00E 1 12 0.0 0.0 [26]238. CHOCHO 1 HO 5 HCO 1 CO 1 H O2 2 2 1.70E 1 12 0.0 10700.0 [26]239. CHOCHO 1 CH 5 HCO 1 CO 1 CH3 4 1.74E 1 12 0.0 8440.0 [26]240. CHOCHO 1 O 5 HCO 1 CO 1 HO2 2 1.00E 1 14 0.0 37000.0 [26]241. CH CO(1M) 5 CH 1 CO(1M)3 3 3.00E 1 12 0.0 16722.0 [26]

Low pressure limit: 1.20E 1 15 0.0 12518.0242. CH CO 1 O 5 CO 1 CH2 2 2 1.75E 1 12 0.0 1350.0 [26]243. CH CO 1 H 5 CH 1 CO2 3 2.71E 1 04 2.75 714.0 [29]244. CH CO 1 H 5 HCCO 1 H2 2 2.00E 1 14 0.0 8000.0 [26]245. CH CO 1 O 5 HCCO 1 OH2 1.00E 1 13 0.0 8000.0 [26]246. CH CO 1 OH 5 HCCO 1 H O2 2 1.00E 1 13 0.0 2000.0 [26]247. CH CO 1 OH 5 CH OH 1 CO2 2 3.73E 1 12 0.0 21013.0 [26]248. CH CO(1M) 5 CH 1 CO(1M)2 2 3.00E 1 14 0.0 70980.0 [26]

Low pressure limit: 3.60E 1 15 0.0 59270.0249. C H 1 H 5 C H 1 H2 2 2 2 4.09E 1 05 2.39 864.3 [26]250. C H 1 O 5 CH 1 CO2 5.00E 1 13 0.0 0.0 [26]251. C H 1 OH 5 HCCO 1 H2 2.00E 1 13 0.0 0.0 [26]252. C H 1 O 5 CO 1 CO 1 H2 2 9.04E 1 12 0.0 2457.0 [26]

(Continued)



shortstandardlong

Table I (Continued)


253. HCCO 1 C H 5 H CCCH 1 CO2 2 2 1.00E 1 11 0.0 3000.0 [26]254. HCCO 1 H 5 CH (S) 1 CO2 1.00E 1 14 0.0 0.0 [26]255. HCCO 1 O 5 H 1 CO 1 CO 8.00E 1 13 0.0 0.0 [26]256. HCCO 1 O 5 CH 1 CO2 2.95E 1 13 0.0 1113.0 [26]257. HCCO 1 O 5 HCO 1 CO 1 H2 2.50E 1 08 1.0 0.0 [26]258. HCCO 1 O 5 CO 1 HCO2 2 2.40E 1 11 0.0 2854.0 [26]259. HCCO 1 CH 5 C H 1 CO2 2 5.00E 1 13 0.0 0.0 [26]260. HCCO 1 HCCO 5 C H 1 CO 1 CO2 2 1.00E 1 13 0.0 0.0 [26]261. HCCO 1 OH 5 C O 1 H O2 2 3.00E 1 13 0.0 0.0 [26]262. C O 1 H 5 CH 1 CO2 1.00E 1 13 0.0 0.0 [26]263. C O 1 O 5 CO 1 CO2 5.00E 1 13 0.0 0.0 [26]264. C O 1 OH 5 CO 1 CO 1 H2 2.00E 1 13 0.0 0.0 [26]265. C O 1 O 5 CO 1 CO 1 O2 2 2.00E 1 13 0.0 0.0 [26]

C3 HYDROCARBON SUBMECHANISM266. C H (1M) 5 C H 1 CH (1M)3 8 2 5 3 7.90E 1 22 21.8 88629.0 [26]

Low pressure limit: 7.24E 1 27 22.88 67448.0Troe Parameters: a 5 1.0, T*** 5 1.0E 2 15,T* 5 1500.0, T** 5 1.0E 1 15Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

267. C H 1 HO 5 NC H 1 H O3 8 2 3 7 2 2 4.76E 1 04 2.55 16492.0 [26]268. C H 1 HO 5 IC H 1 H O3 8 2 3 7 2 2 9.64E 1 03 2.6 13909.0 [26]269. C H 1 OH 5 NC H 1 H O3 8 3 7 2 3.16E 1 07 1.8 934.0 [26]270. C H 1 OH 5 IC H 1 H O3 8 3 7 2 7.08E 1 06 1.9 2159.0 [26]271. C H 1 O 5 NC H 1 OH3 8 3 7 3.73E 1 06 2.4 5504.0 [26]272. C H 1 O 5 IC H 1 OH3 8 3 7 5.48E 1 05 2.5 3139.0 [26]273. C H 1 H 5 IC H 1 H3 8 3 7 2 1.30E 1 06 2.4 4471.0 [26]274. C H 1 H 5 NC H 1 H3 8 3 7 2 1.33E 1 06 2.54 6756.0 [26]275. C H 1 CH 5 NC H 1 CH3 8 3 3 7 4 9.04E 2 01 3.65 7153.0 [26]276. C H 1 CH 5 IC H 1 CH3 8 3 3 7 4 1.51E 1 00 3.46 5480.0 [26]277. C H 1 C H 5 IC H 1 C H3 8 2 3 3 7 2 4 1.00E 1 03 3.1 8830.0 [26]278. C H 1 C H 5 NC H 1 C H3 8 2 3 3 7 2 4 6.00E 1 02 3.3 10500.0 [26]279. C H 1 C H 5 IC H 1 C H3 8 2 5 3 7 2 6 1.51E 1 00 3.46 7470.0 [26]280. C H 1 C H 5 NC H 1 C H3 8 2 5 3 7 2 6 9.03E 2 01 3.65 9140.0 [26]281. C H 1 AC H 5 C H 1 NC H3 8 3 5 3 6 3 7 2.35E 1 02 3.3 19842.0 [26]282. C H 1 AC H 5 C H 1 IC H3 8 3 5 3 6 3 7 7.83E 1 01 3.3 18169.0 [26]283. NC H (1M) 5 C H 1 CH (1M)3 7 2 4 3 1.23E 1 13 20.1 30202.0 [26]

Low pressure limit: 5.49E 1 49 210.0 35766.0 [26]Troe Parameters: a 5 2.17, T*** 5 1.0E 2 15,T* 5 251.0, T** 5 1185.0Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

284. C H 1 H(1M) 5 IC H (1M)3 6 3 7 5.70E 1 09 1.16 874.0 [26]Low pressure limit: 1.64E 1 54 211.1 9364.0Troe Parameters: a 5 1.0, T*** 5 1.0E 2 15,T* 5 260.0, T** 5 3000.0Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

285. NC H 1 O 5 C H 1 H O3 7 2 3 6 2 2 1.88E 1 20 22.69 7109.0 [72]286. IC H 1 O 5 C H 1 H O3 7 2 3 6 2 2 3.83E 1 26 24.44 7724.0 [72]287. IC H 1 H 5 C H 1 CH3 7 2 5 3 5.00E 1 13 0.0 0.0 [26]288. NC H 1 H 5 C H 1 CH3 7 2 5 3 1.00E 1 14 0.0 0.0 [26]289. NC H 1 HO 5 C H 1 O3 7 2 3 8 2 3.00E 1 12 0.0 0.0 (u)290. IC H 1 HO 5 C H 1 O3 7 2 3 8 2 3.00E 1 12 0.0 0.0 (u)

(Continued)

194 MARINOV


shortstandardlong

Table I (Continued)


291. ‡PC H 1 H 5 C H3 5 3 6 1.00E 1 14 0.0 0.0 [26]292. ‡SC H 1 H 5 C H3 5 3 6 1.00E 1 14 0.0 0.0 [26]293. C H 5 C H 1 CH3 6 2 2 4 2.50E 1 12 0.0 70000.0 [26]294. ‡C H 5 AC H 1 H3 6 3 4 2 3.00E 1 13 0.0 80000.0 [26]295. C H 1 HO 5 AC H 1 H O3 6 2 3 5 2 2 9.64E 1 03 2.6 13910.0 [26]296. C H 1 OH 5 AC H 1 H O3 6 3 5 2 3.12E 1 06 2.0 2298.0 [26]297. C H 1 OH 5 SC H 1 H O3 6 3 5 2 1.11E 1 06 2.0 1451.0 [26]298. C H 1 OH 5 PC H 1 H O3 6 3 5 2 2.11E 1 06 2.0 2778.0 [26]299. C H 1 O 5 CH CHCO 1 H 1 H3 6 3 5.01E 1 07 1.76 76.0 [26]300. C H 1 O 5 C H 1 HCO3 6 2 5 1.58E 1 07 1.76 21216.0 [26]301. C H 1 O 5 AC H 1 OH3 6 3 5 5.24E 1 11 0.7 5884.0 [26]302. C H 1 O 5 PC H 1 OH3 6 3 5 1.20E 1 11 0.7 8959.0 [26]303. C H 1 O 5 SC H 1 OH3 6 3 5 6.03E 1 10 0.7 7632.0 [26]304. C H 1 H 5 C H 1 CH3 6 2 4 3 7.23E 1 12 0.0 1302.0 [26]305. C H 1 H 5 AC H 1 H3 6 3 5 2 1.73E 1 05 2.5 2492.0 [26]306. C H 1 H 5 SC H 1 H3 6 3 5 2 4.09E 1 05 2.5 9794.0 [26]307. C H 1 H 5 PC H 1 H3 6 3 5 2 8.04E 1 05 2.5 12284.0 [26]308. C H 1 CH 5 AC H 1 CH3 6 3 3 5 4 2.22E 1 00 3.5 5675.0 [26]309. C H 1 CH 5 SC H 1 CH3 6 3 3 5 4 8.43E 2 01 3.5 11656.0 [26]310. C H 1 CH 5 PC H 1 CH3 6 3 3 5 4 1.35E 1 00 3.5 12848.0 [26]311. C H 1 HCO 5 AC H 1 CH O3 6 3 5 2 1.08E 1 07 1.9 17010.0 [26]312. CH CHCO 1 OH 5 CH CHCO 1 H O3 2 2 4.00E 1 06 2.0 0.0 [26]313. CH CHCO 1 O 5 CH CHCO 1 OH3 2 7.60E 1 08 1.5 8500.0 [26]314. CH CHCO 1 H 5 CH CHCO 1 H3 2 2 2.00E 1 05 2.5 2500.0 [26]315 CH CHCO 1 H 5 C H 1 CO3 2 5 2.00E 1 13 0.0 2000.0 [26]316. CH CHCO 1 O 5 CH 1 HCO 1 CO3 3 3.00E 1 07 2.0 0.0 [26]317. CH CHCHO 1 OH 5 CH CHCO 1 H O2 2 2 1.00E 1 13 0.0 0.0 [26]318. CH CHCHO 1 O 5 CH CHCO 1 OH2 2 7.24E 1 12 0.0 1970.0 [26]319. CH CHCHO 1 O 5 CH CO 1 HCO 1 H2 2 5.01E 1 07 1.76 76.0 [26]320. CH CHCHO 1 H 5 CH CHCO 1 H2 2 2 3.98E 1 13 0.0 4200.0 [26]321. CH CHCHO 1 H 5 C H 1 HCO2 2 4 2.00E 1 13 0.0 3500.0 [26]322. CH CHCHO 1 O 5 CH CHCO 1 HO2 2 2 2 3.00E 1 13 0.0 36000.0 [26]323. CH CHCO 5 C H 1 CO2 2 3 1.00E 1 14 0.0 34000.0 [26]324. CH CHCO 1 O 5 C H 1 CO2 2 3 2 1.00E 1 14 0.0 0.0 [26]325. AC H 1 O 5 CH CHCHO 1 OH3 5 2 2 1.82E 1 13 20.41 22859.0 [26]326. AC H 1 O 5 AC H 1 HO3 5 2 3 4 2 4.99E 1 15 21.4 22428.0 [26]327. AC H 1 O 5 CH HCO 1 CH O3 5 2 2 2 1.06E 1 10 0.34 12838.0 [26]328. AC H 1 O 5 C H 1 CH O 1 OH3 5 2 2 2 2 2.78E 1 25 24.8 15468.0 [26]329. AC H 1 HO 5 CH CHCH O 1 OH3 5 2 2 2 1.00E 1 13 0.0 0.0 [26]330. AC H 1 HO 5 C H 1 O3 5 2 3 6 2 3.00E 1 12 0.0 0.0 [75]331. AC H 1 OH 5 AC H 1 H O3 5 3 4 2 1.00E 1 13 0.0 0.0 [26]332. AC H 1 H 5 AC H 1 H3 5 3 4 2 5.00E 1 13 0.0 0.0 [26]333. AC H 1 H 5 C H3 5 3 6 1.88E 1 26 23.6 5468.0 [26]334. AC H 1 O 5 CH CHCHO 1 H3 5 2 1.81E 1 14 0.0 0.0 [26]335. AC H 1 CH 5 AC H 1 CH3 5 3 3 4 4 3.02E 1 12 20.32 2131.0 [26]336. PC H 1 O 5 CH HCO 1 HCO3 5 2 3 1.09E 1 23 23.29 3892.0 [26]337. PC H 1 O 5 CH CHCO 1 H 1 O3 5 2 3 1.60E 1 15 20.78 3135.0 [26]338. PC H 1 O 5 CH CHCO 1 H3 5 3 1.00E 1 14 0.0 0.0 [26]339. PC H 1 H 5 PC H 1 H3 5 3 4 2 2.00E 1 13 0.0 0.0 [26]340. PC H 1 OH 5 PC H 1 H O3 5 3 4 2 1.00E 1 13 0.0 0.0 [26]341. PC H 1 H 5 AC H 1 H3 5 3 5 1.00E 1 14 0.0 0.0 [26]342. SC H 1 H 5 AC H 1 H3 5 3 5 1.00E 1 14 0.0 0.0 [26]343. SC H 1 O 5 CH CO 1 CH O3 5 2 3 2 1.09E 1 22 23.29 3892.0 [26]344. SC H 1 O 5 CH CO 1 CH3 5 2 3 1.00E 1 14 0.0 0.0 [26]

(Continued)



shortstandardlong

Table I (Continued)


345. SC H 1 H 5 PC H 1 H3 5 3 4 2 4.00E 1 13 0.0 0.0 [26]346. SC H 1 OH 5 PC H 1 H O3 5 3 4 2 2.00E 1 13 0.0 0.0 [26]347. CH CHCH O 1 O 5 CH CHCHO 1 HO2 2 2 2 2 4.00E 1 10 0.0 1100.0 (a)348. CH CHCH O 1 CO 5 AC H 1 CO2 2 3 5 2 4.68E 1 02 3.16 5380.0 (a)349. CH CHCH O 1 H 5 AC H 1 H O2 2 3 4 2 3.00E 1 13 0.0 0.0 (a)350. CH CHCHO 1 H(1M) 5 CH CHCH O(1M)2 2 2 5.40E 1 11 0.454 2600.0 (a)

Low pressure limit: 1.50E 1 30 24.80 5560.0Troe Parameters: a 5 0.78, T*** 5 94.,T* 5 1555., T** 5 4200.Enhanced Third Body Efficiencies:H O 5 5.0,2

351. AC H 1 H 5 H CCCH 1 H3 4 2 2 2.00E 1 07 2.0 5000.0 [29]352. AC H 1 O 5 C H 1 CO3 4 2 4 1.34E 1 07 1.88 179.0 [26]353. AC H 1 OH 5 H CCCH 1 H O3 4 2 2 1.00E 1 07 2.0 1000.0 [29]354. AC H 1 CH 5 H CCCH 1 CH3 4 3 2 4 1.50E 1 00 3.5 5600.0 [26]355. AC H 5 PC H3 4 3 4 1.48E 1 13 0.0 60401.0 [29]356. PC H 1 H 5 H CCCH 1 H3 4 2 2 2.00E 1 07 2.0 5000.0 [29]357. PC H 1 O 5 C H 1 CO3 4 2 4 1.50E 1 13 0.0 2102.0 [26]358. PC H 1 OH 5 H CCCH 1 H O3 4 2 2 1.00E 1 07 2.0 1000.0 [29]359. PC H 1 CH 5 H CCCH 1 CH3 4 3 2 4 1.50E 1 00 3.5 5600.0 [26]360. PC H 1 H 5 CH 1 C H3 4 3 2 2 5.12E 1 10 1.0 2060.0 [29]361. PC H 1 H(1M) 5 SC H (1M)3 4 3 5 6.50E 1 12 0.0 2000.0 [26]

Low pressure limit: 8.45E 1 39 27.27 6577.0362. AC H 1 H(1M) 5 AC H (1M)3 4 3 5 1.20E 1 11 0.69 3007.0 [26]

Low pressure limit: 5.56E 1 33 25.0 4448.0363. AC H 1 H(1M) 5 SC H (1M)3 4 3 5 8.49E 1 12 0.0 2000.0 [26]

Low pressure limit: 1.11E 1 34 25.0 4448.0364. H CCCH 1 O 5 CH CO 1 HCO2 2 2 3.00E 1 10 0.0 2868.0 [26]365. H CCCH 1 O 5 CH O 1 C H2 2 2 1.40E 1 14 0.0 0.0 [75]366. H CCCH 1 H 5 C H 1 H2 3 2 2 5.00E 1 13 0.0 1000.0 [75]367. H CCCH 1 OH 5 C H 1 H O2 3 2 2 2.00E 1 13 0.0 0.0 [26]368. H CCCH 1 H(1M) 5 AC H (1M)2 3 4 1.66E 1 15 20.37 0.0 [25]

Low pressure limit: 3.36E 1 45 28.52 6293.0Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

O 5 2.0, C H 5 2.02 2 2

369. H CCCH 1 H(1M) 5 PC H (1M)2 3 4 1.66E 1 15 20.37 0.0 [25]Low pressure limit: 8.78E 1 45 28.9 7974.0Enhanced Third Body Efficiencies:H O 5 5.0, H 5 2.0, CO 5 3.0, CO 5 2.02 2 2

O 5 2.0, C H 5 2.02 2 2

(Continued)

196 MARINOV


shortstandardlong

tion found for each model compound were used and theoverall measured rate constant was implemented as aconstraint for H-atom abstraction from ethanol. The re-action path degeneracy associated with the number ofH-atoms available for abstraction between ethanol andthe model compounds were included in the branchingratio calculations. The equations used in the branchingratio determination for re-C H OH 1 X 4 Products2 5

actions are shown below:

a a K /K 5 R1 (1)1 2 sm xm

b b K /K 5 R2 (2)1 2 pm sm

K 5 K R2/((1/R1) 1 R2 1 1) (3)p overall

K 5 K /((1/R1) 1 R2 1 1) (4)s overall

K 5 (K /R1)/((1/R1) 1 R2 1 1) (5)x overall

K 5 K 1 K 1 K (6)overall p s x

Table I (Continued)


370. C H 1 O 5 HCCO 1 CO 1 H3 2 2 2.00E 1 12 0.0 1000.0 [75]371. C H 1 O 5 C H 1 CO3 2 2 2 1.00E 1 14 0.0 0.0 [75]372. C H 1 OH 5 C H 1 HCO3 2 2 2 5.00E 1 13 0.0 0.0 [25]

indicates reverse rate not included.“ : ”reaction in the Lindemann–Hinshelwood form:a Fall-off

k 5 k [M]/(1 1 k [M]/k )o o `

reaction in the Troe form:b Fall-off(k 5 k [M]/(1 1 k [M]/k )) Fo o `

2 21log F 5 (1 1 (k/(N 2 d k)) ) log F ; k 5 log(k [M]/k ) 1 Ccent o `

C 5 20.4 2 0.67 log F ; N 5 0.75 2 1.27 log F ; d 5 0.14cent cent

F 5 (1 2 a) exp(2T/T***) 1 a exp(2T/T*) 1 exp(2T**/T)cent

(1CH2); iC3H7 (iso-C3H7, CH3CHCH3); nC3H7 (n-C3H7, CH2CH2CH3); aC3H5 (allyl, CH2CHCH2); pC3H5 (2-methylvinyl,‡ CH (s)2

HCCHCH3); sC3H5 (1-methylvinyl, CH2CCH3); aC3H4 (allene, H2CCCH2); pC3H4 (propyne, H3CCCH).(a) Estimate

Equation analysis performed using UNIMOL program [50].(b) RRKM/Masterparameters obtained from Walch [59] for RRKM/Master Equation analysis. Calculations were performed for the 1000–2000K(c) Input

temperature range with an applied energy transfer value of 21,DE. 5 500 cm .down

height obtained from [76].(d) Barrierto reaction where(e) Analogy CH OH 1 X 5 CH O 1 XH X 5 {OH,H}.3 3

to reaction where(f) Analogy CH CHO 1 X 5 CH CO 1 XH X 5 {OH,H,CH ,HO ,O}.3 3 3 2

text.(g) Seetext. Overall rate expression for is 3.21E10 T0.72 cm3/mol/sec [39,43].(h) See C H OH 1 OH 5 Products2 5

text. Applied T2.0 fit to the low temperature data of Aders and Wagner [77] for rate expression extrap-(i) See C H OH 1 H 5 Products2 5

olation to high temperatures.text. Overall rate expression for is 6.0E5 exp(2931 k/T) cm3/mol/sec [78]. Branching ratio of 0.3512.46(j) See C H OH 1 O 5 Products T2 5

exp(1489 K/T) [78] was used for since no rate constant measurements exist for thek /kC H OH1O5CH CHOH1OH C H OH1O5CH CH OH1OH2 5 3 2 5 3 2

reaction.CH OH 1 O 5 CH O 1 OH3 3

T3.3 fit to the low temperature data of Gray and Herod [42] for rate expression extrapolation to(k) Applied C H OH 1 CH 5 Products2 5 3

high temperatures. The rate expressions from curve B are 1.6E2 T 3.21 exp(24869 K/T) cm3/mol/sec for C H OH 1 CH 5 C H OH 12 5 3 2 4

8.37E2 T 3.02 exp(24027 K/T) cm3/mol/sec for and 3.62E2 T2.95 exp(23908 K/T) cm3/mol/secCH ; C H OH 1 CH 5 CH CHOH 1 CH ;4 2 5 3 3 4

for C H OH 1 CH 5 CH CH O 1 CH .2 5 3 3 2 4

to reaction.(l) Analogy CH O 1 CO3

to reaction.(m) Analogy CH OH 1 O2 2

reduced by a factor of 1.5.(n) A-factorratios were obtained by treating the relative rates of H-atom abstraction as described in the text. The rate expressions used(o) Branching

for aldehydic H-atom (CH2O) abstraction and secondary H-atom (C3H8) abstraction were respectively taken from Baulch [79] and Marinov[26]. Model compounds selected were formaldehyde (CH2O) and propane (C3H8).

rate expression for is 5.84E12 exp(2910 K/T) cm3/mol/sec [79].(p) Overall CH HCO 1 O 5 Products3

rate expression for is 4.095E9 T1.16 exp(21210 K/T) cm3/mol/sec [79].(q) Overall CH HCO 1 H 5 Products3

rate expression for is T 5.6 exp(21240 K/T) cm3/mol/sec [79].(r) Overall CH HCO 1 CH 5 Products 1.987E 2 63 3

rate expression for is 3.01E12 exp(26000 K/T) cm3/mol/sec [79].(s) Overall CH HCO 1 HO 5 Products3 2

to(t) Analogy CH 1 HO 5 CH O 1 OH.3 2 3

to [65] and a [74].(v) Analogy CH 1 HO 5 CH 1 O C H 1 H 1 HO 5 C H 1 O3 2 4 2 3 5 5 2 3 6 2



shortstandardlong

Kpm 5 rate constant for abstracting a primary hy-drogen (Hp) in the model compound (e.g.,propane)

Ksm 5 rate constant for abstracting a secondary hy-drogen (Hs) in the model compound (e.g.,propane and methanol)

Kxm 5 rate constant for abstracting a hydrogen fromthe hydroxyl group (Hx) in the model com-pound (e.g., methanol)

Kp 5 rate constant for abstracting a primary hy-drogen (Hp) in ethanol

Ks 5 rate constant for abstracting a secondary hy-drogen (Hs) in ethanol

Kx 5 rate constant for abstracting a hydrogen fromthe hydroxyl (OH) group (Hx) in ethanol

a1 5 The number of hydrogens found on the hy-droxyl group (Hx) divided by the number ofsecondary hydrogens (Hs) in the model com-pound (e.g., methanol)

a2 5 The number of secondary hydrogens (Hx) di-vided by the number of hydrogens found onthe hydroxyl group (Hx) in ethanol

Table II Thermodynamic Properties for Selected Species Units: kcal/mol for DHf, cal/mol/K for S and Cp

Species DH (298 K)f S(298 K) Cp(300 K) Cp(400 K) Cp(500 K) Cp(600 K) Cp(800 K) Cp(1000 K) Cp(2500 K)

HO2 3.50 54.77(b) 8.40(b) 8.92 9.42 9.90 10.72 11.34 12.09CH2

(a) 93.50 46.71 8.19 8.57 8.93 9.28 9.93 10.52 11.75CH2(s)(a) 102.50 45.10 7.91 8.33 8.72 9.11 9.83 10.49 11.86CH2OH 22.10(c) 58.87(b) 11.32(b) 12.94 14.38 15.62 17.54 18.79 20.95C2H(d) 135.0 49.55 8.90 9.63 10.22 10.72 11.54 12.18 13.31C2H3

(a) 70.40 55.50 9.88 11.37 12.82 14.20 16.70 18.74 21.83C2H5

(a) 28.73 59.02 11.85 14.44 16.81 18.98 22.70 25.64 30.20HCOH(a) 23.33 55.42 9.83 12.88 15.17 16.85 18.89 19.84 20.65HCOOH(e) 290.47 59.47 10.95 13.04 14.96 16.68 19.44 21.37 23.47CH2HCO(d) 6.00 64.00 13.18 15.15 16.96 18.60 21.30 23.34 26.35CHOCHO(a) 250.60 68.16 14.90 17.51 19.69 21.48 24.15 25.89 28.10HOC2H4O2

(f) 238.60 84.71 21.34 24.77 27.71 30.25 34.42 37.74 43.67IC3H7

(a) 21.51 68.88 16.90 20.76 24.51 27.81 33.39 37.73 44.35NC3H7

(a) 24.05 69.16 17.18 21.71 25.54 28.81 34.00 37.91 44.36AC3H5

†(a) 38.64 64.73 16.07 19.55 22.72 25.53 29.99 32.89 37.43PC3H5

(a) 64.75 68.74 15.54 18.56 21.44 24.12 28.65 31.68 36.13SC3H5

(a) 61.09 69.24 15.45 18.38 21.21 23.89 28.50 31.61 36.09CH2CHCH2O(a) 22.40 69.59 17.12 21.25 24.75 27.73 32.39 36.44 41.11CH2CHCHO(f) 216.05 67.40 16.37 20.06 23.20 25.86 29.99 32.94 37.18CH2CHCO(a) 14.85 68.08 15.24 18.46 21.15 23.38 26.79 29.15 32.51CH3CHCO(a) 220.06 67.75 17.63 20.72 23.39 25.71 29.42 32.19 36.43PC3H4

(d) 45.77 58.89 14.52 17.06 19.40 21.54 25.16 27.90 31.79AC3H4

(d) 47.63 57.94 14.25 16.97 19.46 21.71 25.45 28.20 32.06H2CCCH(d) 83.04 61.48 15.84 17.74 19.48 21.01 23.43 25.01 27.55C3H2

(d) 129.6 64.81 14.93 16.10 16.91 17.55 18.72 19.74 21.22C2H5OH(e) 256.15 67.05 15.67 19.31 22.84 25.96 30.59 34.15 39.53C2H4OH(f) 28.20 68.19 15.48 18.84 21.70 24.11 27.87 30.58 34.73CH3CHOH(f) 210.30 62.69 14.64 17.64 20.37 22.84 26.98 30.13 34.72CH3CH2O(f) 24.10 62.21 14.08 17.72 20.85 23.53 27.75 30.80 35.32

(allyl, CH2CHCH2); pC3H5 (n-C3H5, 1-propenyl, CH3CHCH); sC3H5 (i-C3H5, 2-propenyl, CH3CCH2);† aC H3 5

[26]) (b) (CHEMKIN Thermodynamic Database, [32]) (c) See Text (d) [81] (e) (Burcat and McBride, [33]) (f) Group Additivity/(a) (Marinov,Difference method

b1 5 The number of secondary hydrogens (Hs) di-vided by the number of primary hydrogens(Hp) in the model compound (e.g., propane)

b2 5 The number of primary hydrogens (Hp) di-vided by the number of secondary hydrogens(Hs) in ethanol

R1 5 ratio of rate constants from the model com-pound (e.g., methanol) corrected for thenumber of H-atoms available for abstractionin ethanol

R2 5 ratio of rate constants from the model com-pound (e.g., propane) corrected for the num-ber of H-atoms available for abstraction inethanol

Koverall 5 the total rate constant for C H OH 1 X 42 5

where O, H, andProducts, X 5 {OH,CH3}

198 MARINOV


shortstandardlong

A sample calculation is presented to walk the readerthrough the several steps required in this branchingratio estimation method. The overall rate expressionfor was obtained by us-C H OH 1 OH 4 Products2 5

ing the rate coefficient measurements of Hess andTully [39] in the 293–750 K temperature range andthe shock tube results of Bott and Cohen [43] around1200 K. The curve fitted rate expression of (Koverall 5 )3.21E10 T0.72 cm3/mol/sec was obtained from the dataacquired in the two studies, where T is temperature inunits of Kelvin. The relative branching ratio betweenthe secondary hydrogen and the hydrogen on the hy-droxyl group in ethanol was obtained with methanolas the model compound. Tsang [44] performed a de-tailed literature review and theoretical analysis workon the reaction. TheCH OH 1 OH 4 Products3

branching ratio expression obtained from the Tsang

study for andCH OH 1 OH 4 CH OH 1 H O3 2 2

wasCH OH 1 OH 4 CH O 1 H O (K /K 5 )3 3 2 sm xm

The ratio of the rate con-0.2703 exp (1020 K/T).stants from the methanol model compound correctedfor the number of H-atoms available (i.e., a1 5 1/3, a2

5 2/1) for abstraction in ethanol yields (R1 5 )(1/3)(2/1)(0.2703 exp(1020K/T)) or 0.4055 exp(1020K/T). The relative branching ratio between the primaryand secondary hydrogens in ethanol was obtained withpropane as the model compound. Cohen [45] per-formed a detailed literature review and theoreticalanalysis work on the reac-C H 1 OH 4 Products3 8

tion. The rate expressions obtained from the Cohenstudy for andC H 1 OH 4 nC H 1 H O C H 13 8 3 7 2 3 8

were exp1.8OH 4 iC H 1 H O (K 5 ) 3.16E7 T3 7 2 pm

(2470 K/T) cm3/mol/sec and 7.08E6 T1.9(K 5 )sm

exp(80 K/T) cm3/mol/sec, respectively. The ratio ofthe rate constants from the propane model compoundcorrected for the number of H-atoms available for ab-straction in ethanol yields (R2 5 ) (2/6)(3/2)

exp(2550 K/T)) or20.10 20.10(4.463E0 T 2.2315E0 Texp(2550 K/T). This information allows equations(3)– (5) to be solved, and the rate constants andbranching ratios are obtained for the three distinct sitesof H-atom abstraction from ethanol by the OH radical.

C2H5OH 1 OH !: Products

The calculated branching ratio values (i.e., Kp/Koverall,Ks/Koverall, and Kx/Koverall) are shown in Figure 2 alongwith the direct measurements and indirect determina-tions of the branching ratios for the C H OH 12 5

reaction. The numerical results showOH 4 Productsa branching ratio value for K /K 5p overall

of 0.72 at 300 K. Thisk /kC H OH1OH 4 CH CHOH1H O overall2 5 3 2

value is in very good agreement with the direct productstudy of Meier et al. [38]. Meier used mass spectrom-etry to show that C H OH 1 OH 4 CH CHOH 12 5 3

accounted for 75 6 15% of the overall reactionH O2

rate at 300 K. Around 600 K, Hess and Tully [39]monitored the decay rates of 18OH and 16OH radicalsin the presence of ethanol to determine16(C H OH)2 5

the rate constant contribution from C H OH 12 5

(or This prod-OH 4 C H OH CH CH OH) 1 H O.2 4 2 2 2

uct channel lead to the formation of 16CH CH OH2 2

whereupon the 16OH radical is regenerated by the fastdissociation reaction 16 16CH CH OH 4 C H 1 OH.2 2 2 4

They found the measured rate constant for the reactionof 18OH radical with ethanol is ca. 18% higher thanthat measured for the 16OH reaction with ethanol.Therefore, the C H OH 1 OH 4 C H OH 1 H O2 5 2 4 2

product channel accounted for approximately 15%–20% of the total rate constant. This study’s branchingratio determination at 600K suggests a value around

19% for Ks/K 5 k /koverall C H OH1OH 4 C H OH1H O overall2 5 2 4 2

that is in excellent agreement to the Hess and Tullyexperimental finding. Two indirect determinations ofthe branching ratios for C H OH 1 OH 4 Products2 5

were presented by Bott and Cohen [43], and Nortonand Dryer [6]. Bott and Cohen performed transitionstate theory (TST) calculations by constraining thebranching flux at 298 K for the C H OH 1 OH 42 5

channel at 75%, and assumingCH CHOH 1 H O3 2

has a similarC H OH 1 OH 4 CH CH O 1 H O2 5 3 2 2

activation energy barrier as CH OH 1 OH 43

The constrained TST calculationsCH O 1 H O.3 2

showed producing C2H4OH:C H OH 1 OH2 5

CH3CHOH:CH3CH2O products by the approximatesplit of 30%:56%:14% at 600 K and 30%:46%:24%in the 1000–1200 K temperature range. The Bott andCohen theoretical determination of the C H OH 12 5

branching ratio at 600 K ov-OH 4 C H OH 1 H O2 4 2

erpredicted the Hess and Tully measurement by a fac-tor of 1.5–2.0. However, their high temperaturebranching ratios agree with the numerical modelingwork on flow reactor ethanol oxidation kinetics byNorton and Dryer (30%:50%:20% at 1100 K). Thisstudy’s branching ratio value of ca. 17% at 1100 K for

is approximatelyC H OH 1 OH 4 C H OH 1 H O2 5 2 4 2

a factor of two lower than the Bott and Cohen, andNorton and Dryer branching ratio determinations.There is also a fairly large discrepancy between thebranching values selected for the CH3CHOH andCH3CH2O product channels as well. This study



shortstandardlong

Figure 2 The branching ratioC H OH 1 OH 4 Products2 5

values are calculated per text discussion for the 300–2000K temperature range. Solid symbols refer to experimentaldata, open symbols refer to chemical kinetic modeling/in-direct determination of the branching ratios. Squares areCH3CHOH branching ratio data. Circles are C2H4OHbranching ratio data. Diamonds are CH3CH2O branching ra-tio data.

advocates the dominance of the productCH CH O3 2

channel at high temperatures with branching ratio val-ues of ca. 55–65% in the 1000–2000 K temperaturerange, and a small relative contribution from theCH3CHOH product channel of ca. 19–27% in the1000–2000 K temperature range. The extrapolated

branching ratioC H OH 1 OH 4 C H OH 1 H O2 5 2 4 2

values to the high temperature condition are consid-ered to be reliable.

C2H5OH 1 O !: Products

In Figure 3, the branching ratio values are shown forthe reaction. Direct mea-C H OH 1 O 4 Products2 5

surements and indirect determinations of the branchingratios are also noted for comparison. The numerical re-sults at 300 K indicate branching ratio values of 0.98for K /K 5 k /k andp overall C H OH1O 4 CH CHOH1H O overall2 5 3 2

0.02 for K /K 5 k /k .x overall C H OH1O 4 CH CH O1H O overall2 5 3 2 2

These values are in very good agreement with the di-rect product study of Washida [40]. Washida usedphotoionization mass spectrometry to show thatC2H5OH 1 O 4 CH3CHOH 1 OH and C2H5OH 1O 4 CH3CH2O 1 OH accounted for 98–100% and0.0–2.0% respectively of the overall rate of reactionat 300 K. In another study, Dutton and co-workers [41]examined the relative importance of the H-atom ab-straction sites between the O9H and C9H groupsin ethanol. They used laser-induced fluorescence un-der crossed-molecular beam conditions to determinethe branching ratio. TheC H OH 1 O C H OD 1 O2 5 2 5

reaction was studied by monitoring the OH and

OD fluorescence signals, and by knowing the OH andOD transition probabilities the relative reactivity of theabstractable H-atom sties could be determined. Theirwork indicated that H-atom abstraction from the hy-droxyl group by O-atom was 2.2 times faster than fromthe C9H group at a translational temperature of 3500K. However, these results must be corrected as an ad-ditional source of OD would be produced through thereaction sequence of C2H5OD 1 O 4 CH2CH2OD 1OH and CH2CH2OD 4 C2H4 1 OD as previouslynoted by Hess and Tully’s mechanistic studies of

above 500 K. This impliesC H OH 4 C H 1 OH2 4 2 4

that H-atom abstraction from the hydroxyl group byO-atom is approximately 1.2 times faster than abstrac-tion from the C9H group at 3500 K. The empiricalapproach shows very good agreement with the Duttonbranching ratio for the CH3CH2O channel at 3500 Kand suggests confidence in this study’s C H OH 12 5

branching ratios over theO 4 CH CH O 1 OH3 2

300–3500 K temperature range. Indirect studies onthe branching ratios were conducted inC H OH 1 O2 5

the 343–413K temperature range by Avramenko andKolensikova [46] and at 923 K by Nalbandyanet al. [47]. Avramenko determined that the

product ratio variedC H OH:CH CHOH:CH CH O2 4 3 3 2

from 35%:48%:17% at 343 K to 28%:42%:30% at 413K in their brief communications paper. Nalbandyanindicated a product ratio of 47%:39%:14% at 923 K.These results do not compare well with this study’sempirically derived branching ratios.

C2H5OH 1 CH3 !: Products

There has been one direct and indirect study on therole of methyl radical abstracting an H-atom from thethree specific abstraction sites of ethanol. Gray andHerod [42] measured the rates of methyl radical attackon the H-atom sites found in the hydroxyl and the alkylgroups in ethanol by examining three isotopically dif-ferent ethanol’s. They found the methylene group wasthe most reactive site, and the methyl group was theleast reactive site at 423 K. Their results showedbranching ratios of 5%:75%:20% corresponding to

formation. In thisC H OH:CH CHOH:CH CH O2 4 3 3 2

study, fair agreement of the empirically derivedbranching ratios to the Gray and Herod direct study isshown as curve B in Figure 4. A branching ratio of13%:60%:27% for C H OH:CH CHOH:CH CH O2 4 3 3 2

formation at 423 K was calculated. However, the cal-culated branching fraction to the CH CHOH 1 CH3 4

products is outside the error bound prescribed by thisstudy for the Gray and Herod measurement, and fur-ther improvement is suggested. A new branching ratio

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Figure 3 The branching ratioC H OH 1 O 4 Products2 5

values as calculated per text discussion for the 300–2000 Ktemperature range. Solid symbols refer to experimental data,open symbols refer to chemical kinetic modeling/indirect de-termination of the branching ratios. Squares are CH3CHOHbranching ratio data. Circles are C2H4OH branching ratiodata. Diamonds are CH3CH2O branching ratio data.

evaluation, shown as curve A, used the (seek /k144 145

Table II) ratio from the low temperature rate constantmeasurements of Gray and Herod [42]. The curve Aresults show (1) better agreement with Gray and Herodmeasured branching ratios, (2) the C H OH 12 5

branching fraction remainsCH 4 CH CH O 1 CH3 3 2 4

essentially the same as curve B, and that (3) a 0.10–0.15 change in value between curve A and B is foundfor the other two channels especially at the higher tem-peratures.

The detailed chemical kinetic modeling work onethanol pyrolysis in a static reactor by Borisov et al.[5] showed the reactionC H OH 1 CH 4 Products2 5 3

was important for describing the product profiles mea-sured at nearly one atmosphere and 800–1100 K. Bestagreement with the product profiles was obtainedwhen using branching ratios of 76%:19%:5% for

at 950 K. This study’sC H OH:CH CHOH:CH CH O2 4 3 3 2

branching ratio value of ca. 28% (curve A) at 950 Kfor is inK /K 5 k /kp overall C H OH1CH 4 C H OH1CH overall2 5 3 2 4 4

poor agreement with the 76% branching ratio valuedetermined by Borisov. This disagreement is due tothe omission of the C H OH(1M) 4 C H 12 5 2 4

reaction in the Borisov detailed chemicalH O(1M)2

kinetic model. The inclusion of the ethanol dehydra-tion reaction to the Borisov mechanism would bringtheir branching fraction for kC H OH1CH 42 5 3

in line with this/kC H OH1CH C H OH1CH 4 Products2 4 4 2 5 3

study’s value.This study recommends using the calculated

branching ratios as shown in curve A in Figure 4. Thecurve A representation is preferred as the Gray and

Herod branching ratio measurement was reproduced,and suggests some degree of credibility to the extrap-olated values at elevated temperatures. The

branching ra-C H OH 1 CH 4 CH CH O 1 CH2 5 3 3 2 4

tio values in curve A or B are very similar especiallyat elevated temperatures, and these branching ratiosare considered to be reliable. Further measurements athigher temperatures would help confirm these branch-ing ratio choices.

C2H5OH 1 H !: Products

The branching ratio estimation procedure was alsoadopted for H-abstraction reactions involvingC2H5OH and H-atom. There have been no directbranching ratio studies for C H OH 1 H 42 5

although Norton and Dryer provide an in-Products,direct branching ratio determination from chemical ki-netic modeling. Their modeling efforts showed abranching ratio of 30%:50%:20% for

formation at 1100 K.C H:OH:CH CHOH:CH CH O2 3 3 2

Figure 5 shows a branching ratio value of 26%:54%:20% at 1100 K that is in fortuitous agreement with theNorton and Dryer branching ratio findings.

C2H5OH 1 HO2 !: Products

The branching ratio estimation procedure could not becarried out for the H-abstraction reactions involvingC2H5OH and the HO2 radical. This is due to a lackof rate constant measurements for the overall

reaction, and a lack ofC H OH 1 HO 4 Products2 5 2



shortstandardlong

Figure 4 The Products branching ra-C H OH 1 CH 42 5 3

tio values as calculated per text discussion for the 300–2000K temperature range. Solid symbols refer to experimentaldata, open symbols refer to chemical kinetic modeling/in-direct determination of the branching ratios. Squares areCH3CHOH branching ratio data. Circles are C2H4OHbranching ratio data. Diamonds are CH3CH2O branching ra-tio data.

Figure 5 The branching ratioC H OH 1 H 4 Products2 5

values as calculated per text discussion for the 300–2000 Ktemperature range. Solid symbols refer to experimental data,open symbols refer to chemical kinetic modeling/indirect de-termination of the branching ratios. Squares are CH3CHOHbranching ratio data. Circles are C2H4OH branching ratiodata. Diamonds are CH3CH2O branching ratio data.

rate constant measurements for the model compoundreaction, . Instead,CH OH 1 HO 4 CH O 1 H O3 2 3 2 2

this study assumed rate expression assignments toandC H OH 1 HO 4 CH CHOH 1 H O2 5 2 3 2 2

asC H OH 1 HO 4 C H OH 1 H O 8.20E 1 32 5 2 2 4 2 2

T2.55 exp(25410 K/T) cm3/mol/sec and 1.23E 1 4T2.55 exp(27927 K/T) cm3/mol/sec, respectively. Inabsence of direct rate constant measurements, theseestimates are highly uncertain.

The rateC H OH 1 HO 4 CH CHOH 1 H O2 5 2 3 2 2

expression was developed by assuming this reactionhad rate constants similar to the CH OH 1 HO 43 2

reaction. The T2.55 expression wasCH OH 1 H O2 2 2

taken from Tsang’s analysis of C H 1 HO 43 8 2

[48] and [49].Products i-C H 1 HO 4 Products4 10 2

The remaining parameters were selected to fit therate constants inCH OH 1 HO 4 CH OH 1 H O3 2 2 2 2

the 750–900 K temperature range. The CH OH 13

rate constants were takenHO 4 CH OH 1 H O2 2 2 2

from Held and Dryer’s high pressure methanol oxi-dation modeling study [82]. The C H OH 1 HO 42 5 2

rate expression was based on theC H OH 1 H O2 4 2 2

rate expression of C H OH 1 HO 4 CH CHOH 12 5 2 3

. A probable error of 63.0 kcal/mol is attributedH O2 2

to the activation energy for C H OH 1 HO 42 5 2

.C H OH 1 H O2 4 2 2

RRKM/Master Equation Calculations forthe Ethanol Decomposition Reactions

In order to determine the degree of falloff and the es-timate of the high pressure limit rate constant forthe andC H OH(1M) 4 CH OH 1 CH (1M)2 5 2 3

bond fission re-C H OH(1M) 4 C H 1 OH(1M)2 5 2 5

actions, RRKM/Master equation theory calculations[50] were performed using the hindered rotationalGorin Model [51]. The Gorin model assumes that theinternal modes of the transition state are vibrations androtations of the separated radical fragments, and thefour low frequency bending modes associated with thebreaking bond are considered to be two 2-dimensionalhindered rotations of the independent radical frag-ments. The transition state is located at the top of thecentrifugal barrier. The vibration frequencies and mo-ments of inertia for ethanol were obtained from thethermodynamic properties study by Green [52]. Thetransition state vibrational frequencies for C9C bondfission were assigned by using the frequencies of the

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Table III Molecular and Transition State Properties Used in RRKM/Master Equation Analysis of the C H OH 42 5

and Decomposition ReactionsCH 1 CH OH C H OH 4 C H 1 OH3 2 2 5 2 5

C H OH 4 CH 1 CH OH2 5 3 2

Transition State: CH ·CH OH3 2

Critical Energy: 86.7 kcal/mola

Frequencies (degeneracy): 573,607,950,1091, 1341,1396(2),1459,1623,2844,3960,3044,3162(2),3650b

Inactive External Rotation 0.10421(cm ): (symmetry 5 1,dimension 5 2)Active External Rotation 0.69621(cm) ): (symmetry 5 1,dimension 5 1)Internal 0.897(1,2), 9.57(1,2)21(cm ): 6.95(symmetry 5 3,dimension 5 1),

C H OH 4 C H 1 OH2 5 2 5

Transition State: C H ·OH2 5


Frequencies (degeneracy): 540,784,975,1138,1175,1366,1440(3),2842,2920,2987,3033,3112,3730b,c

Inactive External Rotation 21(cm ): 0.093 (1,2)Active External Rotation 0.828 (3,1)21(cm) ):Internal 6.09(1,1), 0.726(1,2), 19.29(1,2)21(cm ):

Ground State: C2H5OHFrequencies (degeneracy): (263)d,311,427,801,1040,1067,1104,1242,1270,1320,1391,1456(3),2789(3),3689e

Inactive External Rotation 0.284 (1,2)21(cm ):Active External Rotation 1.213 (1,1)21(cm ):Internal 6.46(3,1)21(cm ):

Lennard-Jones Parameters and Molecular Weight

C2H5OHf: e/K 5 362.6 KB˚s 5 4.53 A Molecular Weight 5 46.0 g/gmol

Argong: e/K 5 136.5 KB˚s 5 3.3 A Molecular Weight 5 39.95 g/gmol

a This Study. b [33]. c [53]. d Replaced low frequency vibration with free internal rotation. e [52]. f [80]. g [32].

methyl radical [33] and the CH2OH radical [33]. Thetransition state vibrational frequencies for the C9Obond fission reaction were assigned by using the fre-quencies of the ethyl radical [33] and the hydroxylradical [53]. The fragment moments of inertia for ro-tation normal to the molecular axis were taken from[33] and [53]. The complete listing of parametersused in the RRKM/Master Equation calculationsfor andC H OH(1M) 4 CH OH 1 CH (1M)2 5 2 3

C2H5OH(1M) 4 C2H5 1 OH(1M) are given in Ta-ble III.

Particular attention was paid to C H OH(1M) 42 5

since this reaction was found toCH 1 CH O(1M)3 2

be one of the most sensitive reactions under shock tubeconditions in the Egolfopoulos et al. and Natarajan/Bhaskaran studies as well as in the present work. TheRRKM calculations were performed by considerationof three adjustable parameters: (i) the rotational con-stant for external and internal rotation, (ii) the criticalenergy, and (iii) the energy transferred per collision.A series of MOPAC PM3 [54] calculations were un-dertaken in order to obtain the geometry of the nearlyseparated fragments for the complex atCH 9CH OH3 2

the top of the centrifugal barrier. These calculationsallowed the rotational constants to be determinedthrough examination of the Van der Waal repulsionsof the rotating fragments. The CH2OH heat of for-mation was allowed to vary from 22.1 kcal/mol [55]to 24.1 kcal/mol [32] when adjusting the critical en-ergy and fitting the shock tube data. Best agreementwas attained with a heat of formation (at 298 K) valueof 22.1 (kcal/mol for CH2OH, and this corresponded

to a final critical energy value of 86.7 kcal/mol inthe RRKM calculations. The energy transferred percollision value was determined to be 500 cm21 inagreement with Tsang’s earlier determination of

for methanol and propane bond fission,DE .down

decomposition at these temperatures [44,48].The high and low pressure limit rate constants

along with the Troe parameters obtained from theRRKM/Master Equation theory calculations for

areC H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

` 21.68 21k 5 5.71E23 T exp(247511 K/T) (s )130

218.84k 7 5 3.11E85 T130

33 exp(256917 K/T) (cm /mol/sec)

F 5 0.5 exp(2T/500 K)cent

1 0.5 exp(2T/825 K) 1 exp(26100 K/T)

Figure 6 shows a comparison of this study’sunimolecularC H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

rate constant at 1 atm with the Borisov [5] and Tsang[44] 1 atm rate expressions in the 1000 K , T ,

range. The Borisov rate expression and1700 KTsang’s RRKM evaluation of ethanol decompositionto methyl and hydroxymethylene differ by approxi-mately one order of magnitude. This study’s

rate expres-C H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

sion agrees with Tsang’s work to within a factor oftwo and agrees with Borisov et al. to within a factorof five. If the CH2OH heat of formation value at 298K were to be lowered from the present value of 22.1kcal/mol to 24.1 kcal/mol, then this study’s

rate con-C H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

stants would nearly lie on top of the Tsang evaluation.In Figure 7, rate constant comparisons at 2.0 bar are



shortstandardlong

Figure 6 Comparison of this study’s rate constants to dataof Tsang [44] and Borisov et al. [5] for the C H OH2 5

reaction at 1 atm. This(1M) 4 CH 1 CH OH(1M)3 2

study’s rate constantsC H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

at 1 atm along with Borisov’s C H OH(1M) 4 C H 12 5 2 5

reaction kinetics are also included. Note: Tsang’sOH(1M)high pressure limit rate constant [62] for C H OH 42 5

along with thermochemistry [44,65] wereCH 1 CH OH3 2

used in the RRKM derivation.

Figure 7 Comparison of this study’s rate constants at 2.0bar against data of Herzler, Manion, and Tsang [56] forC2H5OH(1M) 4 CH3 1 CH2OH(1M) and C2H5OH(1M)4 C2H4 1 H2O(1M) reactions.

shown between this study’s C H OH(1M) 42 5

rate expression and preliminaryCH 1 CH OH(1M)3 2

measurements made by Herzler, Manion, and Tsang[56]. This study underpredicted the measured rate con-stants in the 1200–1300 K temperature range by ap-proximately a factor of three; however, this differencemay be largely attributed to the uncertainty in the mea-sured rate constants and branching ratio for theC2H5OH(1M) 4 CH3 1 CH2OH(1M) andC2H5OH(1M) 4 C2H4 1 H2O(1M) reactions. Thisstudy’s rateC H OH(1M) 4 CH 1 CH OH(1M)2 5 3 2

constants are in reasonable accord with Tsang’sRRKM analysis and the recent measurements by Her-zler et al. Therefore, the suggested rate parameters areconsidered acceptable.

The rate con-C H OH(1M) 4 C H 1 OH(1M)2 5 2 5

stant calculations were performed in the same man-ner as described for C H OH(1M) 4 CH 12 5 3

The high and low pressure limit rateCH OH(1M).2

constants along with the Troe parameters obtainedfrom RRKM/Master Equation theory for C H OH2 5

are(1M) 4 C H 1 OH(1M)2 5

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An energy transfer per collision value ,DE . 5down

was applied in the rate constant analysis.21500 cmAdditional RRKM/Master Equation theory calcu-

lations were carried out to examine the role of H2Oand H2 elimination reactions in the ethanol decom-position process. The input parameters required forthese calculations are shown in Table IV. The H2Oand H2 elimination reactions are complex fission re-actions that involve a four-centered transition state.Benson’s rules for transition state frequencies [34]were applied, and a critical energy was selected tomatch the literature reviewed critical and activationenergies. These critical energies are 64.0–67.0 kcal/mol [57,58] and 91.9 kcal/mol [59,60] respectively for

Table IV Molecular and Transition State Properties Used in RRKM/Master Equation Analysis of the C H OH 42 5

and Decomposition ReactionsCH H 1 H O C H OH 4 CH HCO 1 H2 4 2 2 5 3 2

C H OH 4 C H 1 H O2 5 2 4 2

Transition State: C H ·H O2 4 2


Frequencies (degeneracy): 335,400,700(4),1000(2),1150(2),1300,1450(2),2200(2),3100(4),3700b

Inactive External Rotation 0.28421(cm ): (symmetry 5 1,dimension 5 2)Active External Rotation 1.213 Optical21(cm) ): (symmetry 5 1,dimension 5 1); Isomer 5 2

C H OH 4 CH HCO 1 H2 5 3 2

Transition State: CH HCO·H3 2

Critical Energy: 91.9 kcal/molc

Frequencies (degeneracy): 585,800,1000(2),1150(4),1400,1450(2),2200(2),3100(4)b

Inactive External Rotation 21(cm ): 0.284 (1,2)Active External Rotation 1.213 (1,1); Optical21(cm ): Isomer 5 1

Ground State: C2H5OHFrequencies (degeneracy): 263,311,427,801,1040,1067,1104,1242,1270,1320,1391,1456(3),2789(3),3689d

Inactive External Rotation 0.284 (1,2)21(cm ):Active External Rotation 1.213 (1,1); Optical21(cm ): Isomer 5 1

Lennard-Jones Parameters and Molecular Weight

C2H5OHe: e/K 5 362.6 KB˚s 5 4.53 A Molecular Weight 5 46.0 g/gmol

Argonf: e/K 5 136.5 KB˚s 5 3.3 A Molecular Weight 5 39.95 g/gmol

a This Study and [56,57,58,61]. b [34]. c Assumed critical energy for had same value asC H OH 4 CH HCO 1 H CH OH 4 CH O 12 5 3 2 3 2

[59]. d [52]. e [80]. f [32].H2

` 21.54 21k 5 1.25E23 T exp(248317 K/T) (s )131

218.8k 7 5 3.25E85 T131


F 5 0.5 exp(2T/300 K) 1 0.5 exp(2T/900 K)cent

1exp(25000 K/T)

H2O and H2 elimination from ethanol. A high pressurelimit activation energy for H2O elimination from eth-anol has been suggested to be 66.0 kcal/mol–66.2kcal/mol [56,61]. The transition state frequencies forthe C9C ?O and bends are very low andC9C9OBuncertain. An initial value of 240 cm21 was used forthe transition state C9C ?O bending motion, but thisvalue was later adjusted upward to 335 cm21 to obtainmodeling agreement with the ethylene measurementsin the jet-stirred and turbulent flow reactors. This pointwill be further discussed in the modeling results of thejet-stirred and turbulent flow reactors. Likewise for the

decomposition reaction,C H OH 4 CH HCO 1 H2 5 3 2

the transition state bend frequency was ad-C9C9OBjusted upward by the same factor from an initial valueof 420 cm21 to 585 cm21. The calculated high and lowpressure rate constants and the associated Troe pa-rameters using an energy transfer per collision valueof for21,DE . 5 500 cm C H OH(1M) 4down 2 5

areC H 1 H O(1M)2 4 2

` 0.09 21k 5 2.79E13 T exp(233284 K/T) (s )132

218.85k 7 5 2.57E83 T132


F 5 0.3 exp(2T/350 K) 1 0.7exp(2T/800 K)cent

1exp(23800 K/T)

The high pressure limit isC H OH 4 C H 1 H O2 5 2 4 2

compared to other known data for this reaction asshown in Figure 8. There is a fair amount of scatteramongst the derived rate constants. The Tsang [62]and the Zhitneva and Pshezhetskii [60] rate constantswere derived by examining the rate constants mea-

sured for analogous reactions that eliminate water. TheTsang and Zhitneva activation energy choices werehigher than those found in the recent Butkovskaya andSetser [57,58] analysis and the Herzler, Manion, andTsang [56] recommendation. Butkovskaya and Setserperformed ab initio and RRKM calculations on etha-nol and the four-centered dehydration transition statestep using MP2(FC)/6–31G(d) and MP2(Full)/6–311G(d,p) levels of theory. Their RRKM results werebased on the ab initio data, and the calculated highpressure limit rate constant is substantially faster thanTsang and Zhitneva, but in excellent agreement withHerzler. This study’s high pressure limit is in agree-ment with the Butkovskaya and Setser study and theHerzler et al. recommendation. In Figure 7, rate con-stant comparisons at 2.0 bar are shown between thisstudy’s rate ex-C H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

pression and measurements made by Herzler, Manion,and Tsang [56]. The agreement between the two stud-ies is fairly remarkable, and suggests that this study’s

rate expressionC H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

is entirely reasonable.The multi-parameter rate expression for

was calcu-C H OH(1M) 4 CH HCO 1 H (1M)2 5 3 2

lated and shown to be

` 0.095k 5 7.24E11 T133213 exp (245801 K/T) (s )

219.42k 7 5 4.46E87 T13333 exp(258171 K/T) (cm /mol/sec)

F 5 0.1 exp(2T/900K)cent

10.9 exp(2T/1100 K)1exp(23500 K/T)

21,DE . 5 500 cmdown

A comparison of the high pressure limit rate ex-pressions for C2H5OH decomposition to CH 13

CH OH, C H 1 OH, C H 1 H O, CH CHOH 12 2 5 2 4 2 3

and products isH, C H OH 1 H, CH HCO 1 H2 4 3 2

shown in Figure 9. High pressure rate expressions forC2H5OH decomposition to andCH CHOH 1 H3

products were obtained from TsangCH CH OH 1 H2 2

[62] and these pathways are shown to be unimportant.Interestingly, the ethanol dehydration step was foundto be dominant for temperatures below 1100 K due tothe lower activation energy barrier, while simpleC9C and C9O bond rupture reactions dominate atthe higher temperatures as entropic processes becomeimportant. However, when fall-off considerations at1.0 atm are taken into account as shown in Figure 6,the C2H5OH(1M) 4 reaction isC H 1 H O(1M)2 4 2

the dominant decomposition reaction overC2H5OH(1M) 4 . This is pri-CH 1 CH OH(1M)3 2



shortstandardlong

Figure 8 Comparison of this study’s high pressure limitfor the reaction against data ofC H OH 4 C H 1 H O2 5 2 4 2

Herzler, Manion, and Tsang [56], Butkovskaya and Setser[58], Zhitneva et al. [60], and Tsang [62].

marily due to the lower critical energy found in thewater elimination reaction, which allows for higherlow-pressure limit rate constants to be calculated thanthose found in the C9C or C9O bond fission steps.Ethanol decomposition to is favoredCH 1 CH OH3 2

over since the C9C bond strength isC H 1 OH2 5

weaker than the C9O bond strength by approxi-mately 5.0 kcal/mol. The molecular elimination of H2

from ethanol is extremely slow as a high energy bar-rier, and the loss of the C9O internal rotation at thetransition state limits its rate of decomposition relativeto the other ethanol destruction pathways.

DISCUSSION OF THE NUMERICALMODELING RESULTS

Modeling Ignition Delay in Shock Tubes

Natarajan and Bhaskaran were the first researchers toinvestigate the ignition of ethanol-oxygen-argon gasmixtures behind reflected shock waves. Experimentswere performed for the 1300–1700K temperaturerange, for pressures of 1.0 and 2.0 atm, and for equiv-alence ratios of 0.5, 1.0, and 2.0 [2]. In the experi-mental investigation, the ignition event was identifiedby the first visible light emission, whereupon their ex-perimental ignition delay data were found to be cor-related by the global expression of t 5 1.0 3vis

10215 exp(19221 K/T)[C2H5OH]0.1[O2]20.75[Ar]20.25,is in seconds, and reactant concentrationswhere tvis

are in mol/cm3.Dunphy and Simmie [3,20] later investigated eth-

anol ignition behind reflected shock waves over a pa-rameter space similar to Natarajan and Bhaskaran.Ethanol and oxygen mixtures diluted in argon wereinvestigated for equivalence ratios of 0.25–2.0,

pressures of 1.8 to 4.6 bar, and 1100–1900K. In theexperimental study, the ignition event was defined asthe time to maximum emission of 366 nm radiation,which is attributed to CO2 chemiluminescence. Theoverall results for ignition delay time were correlatedby the expression 214tmax (sec) 5 1.0 3 10co—o

20.315 20.78 0.259exp(15500 K/T)[C H OH] [O ] [Ar] .2 5 2

The numerical simulations of the ignition delay be-hind reflected shock waves were conducted using theSENKIN code assuming an adiabatic, constant volumesystem. This assumption allows for both the temper-ature and pressure to increase during reaction. In mod-eling the Dunphy and Simmie experiments, the theo-retical ignition delay was defined as the time requiredto reach a maximum in the product of the CO and O-atom concentration This definition( 5 tmax ).co—o

was assumed to be equated with the maximum 366 nmradiation occurrence in their experiments. The com-putational results using this definition are shown as thesolid line in Figures 10–12. The modeling of the Na-tarajan and Bhaskaran experiments is difficult sincethe experimental ignition delay was defined as the firstvisible light emission. In modeling their data, the theo-retical ignition delay was defined in two ways. Thecomputed ignition delay time was assumed to be eitherthe maximum in the product CO and O-atom concen-trations as indicated by the solid line or(5tmax )co—o

when the computed OH concentration reached 2.0 31029 mol/cc as indicated by the dashed line in Figures13–15.

In Figures 10–15, the experimental data of Dun-phy/Simmie and Natarajan/Bhaskaran are presentedand these data are compared to the numerical com-putations. The numerical simulations are shown to bein good agreement with both data sets, especially when

206 MARINOV


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Figure 9 Comparison of the high pressure limit rate con-stants for Ethanol decomposition to Products. The rate con-stants for the productC H OH 1 H and CH CHOH 1 H2 4 3

channels were taken from Tsang [62].

Figure 10 Comparison between experimental (symbols)shock tube ignition delay data as investigated by Dunphyand Simmie [3] and the numerical calculations (lines) usingthe chemical kinetic model. Experimental conditions: 1.25%C2H5OH, 7.50% O2, and 91.25% Argon (equivalence ratio5 0.5), and 3.3 bar.

considering the uncertainty associated with the theo-retical ignition delay definition. The thermal decom-position of ethanol has been previously suggested asthe most likely initiation reaction for these condi-tions [63], and was determined to be very importantin this study as noted by the sensitivity analysis resultsshown in Figure 16. Sensitivity analysis was carriedout only for the Dunphy and Simmie data sets sincethey are representative of the conditions examined byNatarajan/Bhaskaran.

Sensitivity analysis was performed by perturbingthe forward and reverse rate constants per reaction bya factor of two, thereby leaving the thermodynamicequilibrium constant unaffected. The sensitivity coef-ficient was then determined by taking the natural log-

arithm of the ignition delay time, calculated with theperturbed reaction kinetics divided by the baseline un-perturbed reaction kinetics, ignition delay time;whereupon the sensitivity coefficient expression isrepresented by

S 5 2ln (t /t ),perturbed kinetics unperturbed kinetics

t 5 ignition delay time

If the sensitivity coefficient exhibits a positive valuethat would indicate an increase in the overall reactivityof the chemical system, a negative value would implya decrease in the overall reactivity. Large sensitivitycoefficient values indicate a strong influence of thereaction kinetics on ethanol ignition delay. The sen-



shortstandardlong

Figure 11 Comparison between experimental (symbols)shock tube ignition delay data as investigated by Dunphyand Simmie [3] and the numerical calculations (lines) usingthe chemical kinetic model. Experimental conditions: 1.25%C2H5OH, 3.75% O2, and 95.0% Argon (equivalence ratio 51.0), and 3.5 bar.

Figure 12 Comparison between experimental (symbols)shock tube ignition delay data as investigated by Dunphyand Simmie [3] and the numerical calculations (lines) usingthe chemical kinetic model. Experimental conditions: 2.5%C2H5OH, 3.75% O2, and 93.25% Argon (equivalence ratio5 2.0), and 3.4 bar.

Figure 13 Comparison between experimental (symbols)shock tube ignition delay data as investigated by Natarajanand Bhaskaran [2] and the numerical calculations (lines) us-ing the chemical kinetic model. Experimental conditions:1.43% C2H5OH, 8.57% O2, and 90% Argon (equivalenceratio 5 0.5), and 1.0 6 0.2 and 2.0 6 0.2 atm.

Figure 14 Comparison between experimental (symbols)shock tube ignition delay data as investigated by Natarajanand Bhaskaran [2] and the numerical calculations (lines) us-ing the chemical kinetic model. Experimental conditions:2.5% C2H5OH, 7.5% O2, and 90% Argon (equivalence ratio5 1.0), and 1.0 6 0.2 and 2.0 6 0.2 atm.

sitivity analysis study was conducted at ethanol-oxy-gen equivalence ratios of 0.5, 1.0, and 2.0 at 3.4 barand 1429 K. The results are shown in Figure 16. Forthe conditions found in the Dunphy and Simmie ex-periments, the six most sensitive reactions are, in orderof their peak sensitivity coefficients for tmax ,co—o

(p) C H OH(1M) ;: CH 1 CH OH(1M) (130)2 5 3 2

(p) C H OH(1M) ;: C H 1 OH(1M) (131)2 5 2 5

(p) O 1 OH ;: O 1 H (2)2

(p) CH 1 HO ;: CH O 1 O (27)3 2 3

(p) HCO 1 M ;: H 1 CO 1 M (112)(q) H 1 HO ;: H 1 O (7)2 2 2

The (q) and (p) signs indicate whether the factor oftwo increase in the reaction rate increases, (q), ordecreases, (p), tmaxco—o . The most sensitive reactionat F 5 0.5 and F 5 1.0 is the well-known branchingreaction The relative sen-H 1 O 4 OH 1 O (p).2

sitivity of the other reactions may be understood onthe basis of their effect on the supply of H-atoms tothe branching reaction. This is shown by the H-atomconsuming reaction, (q), andH 1 HO 4 O 1 H2 2 2

the H-atom producing reactions, 1HCO 1 M 4 HCO 1 M (p) and CH3CH2O 1 M 4 CH3HCO 1H 1 M (p).

The first and second most sensitive reactions, at F5 2.0, are the chain initiating steps C2H5OH(1M) 4 CH3 1 CH2OH(1M) (p) and C2H5OH(1M) 4 C2H5 1 OH(1M) (p). The homolytic scis-sion of the C9C and C9O bond initiates the radicalpool growth necessary for ignition. This is demon-strated by the following consecutive reactions,

C H OH(1M) ;: CH 1 CH OH(1M)2 5 3 2

CH OH 1 O ;: CH O 1 HO2 2 2 2

CH 1 HO ;: CH O 1 OH (1)3 2 3

CH O(1M) ;: CH O 1 H(1M)3 2

H 1 O ;: OH 1 O2

C H OH(1M) ;: C H 1 OH(1M)2 5 2 5

C H (1M) ;: C H 1 H(1M) (2)2 5 2 4

H 1 O ;: OH 1 O2

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Figure 15 Comparison between experimental (symbols)shock tube ignition delay data as investigated by Natarajanand Bhaskaran [2] and the numerical calculations (solid anddashed lines) using the chemical kinetic model. Experimen-tal conditions: 4.0% C2H5OH, 6.0% O2, and 90% Argon(equivalence ratio 5 2.0), and 1.0 6 0.2 and 2.0 6 0.2 atm.See text.

Figure 16 First order sensitivity coefficients of the most important reactions for ignition delay oflean, stoichiometric, and rich ethanol gas mixtures based on the Dunphy and Simmie [3] shock tubeconditions. Nominal pressure of 3.4 bar and temperature of 1429 K.

Modeling agreement to the Dunphy/Simmie and Na-tarajan/Bhaskaran experimental data sets could not beachieved without the use of the C H OH(1M) 42 5

reaction. Interestingly, theCH 1 CH OH(1M)3 2

reaction con-C H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

sumed a greater fraction of the ethanol thanyetC H OH(1M) 4 CH 1 CH O(1M),2 5 3 2

C2H5OH(1M) 4 C2H4 1 H2O(1M) always exhibiteda negligible sensitivity coefficient compared to

This findingC H OH(1M) 4 CH 1 CH OH(1M).2 5 3 2

further demonstrates the importance of homolytic scis-sion of the C9C (and C9O) bond(s) on initiatingthe radical pool growth for ignition.

The (p) reactionCH 1 HO 4 CH O 1 OH3 2 3

followed by CH3O decomposition to CH2O 1 H-atomis the main supply route for H-atoms and OH radicals.The sensitivity shown for this chain propagating re-action is primarily due to the alternative product path-way which leads to chain termination, CH 13

(q). The availability of this alter-HO 4 CH 1 O2 4 2

native reaction path makes the rate constants forCH3 1 HO2 4 CH3O 1 OH and CH3 1 HO2 4CH4 1 O2 important.

The (q) andH 1 HO 4 H 1 O OH 12 2 2

(q) reactions exhibit sensitivityHO 4 H O 1 O2 2 2

primarily due to their influence on the OH radical pool.The OH radical’s primary role is to oxidize the etha-nol. The reaction limits theH 1 HO 4 H 1 O2 2 2

amount of OH radical produced from the alternativeproduct pathway, . The chainH 1 HO 4 OH 1 OH2

terminating nature of this reaction slows the ethanoldestruction rate. The OH 1 HO 4 H O 1 O2 2 2

reaction is chain terminating and removes OH fromthe radical pool, slowing ethanol oxidation viaC H OH 1 OH 4 Products.2 5

Modeling Laminar Burning Velocities inFreely Propagating Flames

Gulder [17] investigated laminar flame speeds (Su) ofethanol-air gas mixtures in a constant volume bombfor a wide range of unburned gas pressures (Pu), 0.1–0.8 MPa, unburned gas temperatures (Tu), 300–500K, and equivalence ratios 0.7–1.4. The maximum un-certainty determined for the measured laminar flamespeeds was 62.0 cm/sec based on the uncertainitiesassociated in the measured unburned gas mixture tem-perature (63.0 K), unburned gas mixture pressure(61%), and equivalence ratio (60.015). The 0.1 MPaexperimental data showed the maximum ethanol-airlaminar flame speed occurred around an equivalenceratio of 1.075 with a value of 47 cm/sec. At elevatedpressures, the ethanol-air laminar speeds decreasedwith pressure while exhibiting the following pressuredependencies with equivalence ratio, S 5 S (P)u u,ref

for f $ 1.0, and for f #20.17 f 20.17 fp pS 5 S (P)u u,ref

1.0, where 300 K and 0.1 MPa are the reference con-ditions. This study used the laminar flame speed dataacquired at 0.1 and 0.2 MPa for model validation.

Egolfopoulos et al. [4] used the counterflow twin-flame technique to measure laminar flame speeds at 1atm pressure, with a temperature range of 363–453K,and an equivalence ratio range of 0.55–1.8. They re-port a maximum uncertainty of 610% to their flame



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Figure 17 Comparison between experimental (symbols) laminar flame speeds as a function ofequivalence ratio as investigated by Gulder [17] and the numerical calculations (lines) using thedetailed chemical kinetic model. The extrapolated data of Egolfopoulos et al. [4] is also shown forcomparison. Model calculations were performed at MPa andP 5 0.1 T 5 300 K.u u

speed data. This study used the experimental data ac-quired at 453 K for model validation.

Figures 17–19 show the comparison of the numer-ical computations with the experimental data obtainedfrom the combustion bomb and the counterflow twinflame. In Figure 17, the extrapolated laminar flamespeed data of Egolfopoulos from flame speed mea-surements performed at higher unburned gas temper-atures 363–453K, are also shown for comparison. Thenumerical results at 0.1 MPa show a slight flame speedoverprediction of ca. 3.0 cm/sec in the 0.70–0.75

equivalence ratio range, and an underprediction of ca.2.0 cm/sec in the 1.05–1.15 equivalence ratio range.Otherwise, very good agreement with the experimen-tal data is shown at the other equivalence ratios. Themodel shows good agreement with the experimentalmeasurements at 0.2 MPa as shown in Figure 18. Themodel is able to correctly predict the location of themaximum flame speed for unburned gas pressures of0.1 MPa and 0.2 MPa. Numerical calculations per-formed for the unburned gas temperature of 453 K and1 atm is shown in Figure 19. The model predicts the

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Figure 18 Comparison between experimental (symbols) laminar flame speeds as a function ofequivalence ratio as investigated by Gulder [17] and the numerical calculations (lines) using thedetailed chemical kinetic model. Experimental conditions were .P 5 0.2 MPa and T 5 300 Ku u

Figure 19 Comparison between experimental (symbols) laminar flame speeds as a function ofequivalence ratio as investigated by Egolofopoulos et al. [4] and the numerical calculations (lines)using the detailed chemical kinetic model. Experimental conditions were P 5 1.0 atm and T 5u u

453 K.

laminar flame speeds very well for the 0.55–1.2 and1.6–1.8 equivalence ratio ranges, but underpredicts themeasurements in the 1.2–1.6 equivalence ratio range.

Sensitivity analysis was performed at an unburned gastemperature of 453 K and 1.0 atm in order to determinethe influence of those chemical reactions and their as-sociated kinetic rate constants on the mass burning rate,

where pu refers to the density of the unburnedM 5 p S ,u u

gas mixture. The normalized sensitivity coefficients werecalculated using the expression, (Ai/M)(DM/DAi), whereAi is the pre-exponential factor of the ith kinetic rateconstant. The results of the sensitivity analysis are pre-sented in Figure 20. At f 5 0.6, CO 1 OH 4

is the most sensitive reaction found in leanCO 1 H2

ethanol-air freely propagating laminar flames, followedin order by H 1 O2 4 OH 1 O, HCO 1 M 4 H 1CO 1 M, H 1 HO2 4 OH 1 OH, CH2HCO 4 CH2CO1 H, and HO2 1 H 4 H2 1 O2. As the equivalenceratios become progressively richer, the H 1 O 42

reaction exhibits the greatest sensitivity, whileOH 1 Othe reaction decreases dramat-CO 1 OH 4 CO 1 H2

ically in sensitivity. The reduction in the CO 1 OH 4sensitivity coefficient is due to a greater num-CO 1 H2

ber of reaction intermediates competing effectively forthe OH radical at progressively richer conditions. Thisphenomena constrains H-atom production from this re-action, and consequently limits its impact on promotingflame propagation.

The sensitivity analysis results indicate the impor-tance of H-atom sources and sinks when modeling eth-anol-air laminar flame speeds. Reactions such as CO1 OH 4 CO2 1 H, HCO 1 M 4 H 1 CO 1 M,CH2HCO 4 CH2CO 1 H, and C2H2 1 H(1M) 4C2H3(1M) exhibit positive sensitivity coefficients,thereby enhancing the flame speed or the overall re-activity of the chemical system since they are the pri-mary producers of H-atoms. The H 1 O 4 OH 12

and reactions, althoughO H 1 HO 4 OH 1 OH2

consumers of H-atoms, also exhibit a positive sensi-tivity coefficient as they produce reactive OH and Oradicals that are necessary to consume ethanol and itsreaction intermediates. The H 1 CH (1M) 43

, andCH (1M), C H 1 H 4 C H 1 H H 14 2 3 2 2 2

reactions are chain terminating re-HO 4 H 1 O2 2 2

actions and retard flame speeds by consuming H-at-oms. The flame propagation is limited by HCO 1

, as this pathway is less reactive thanO 4 CO 1 HO2 2

formyl radical (HCO) decomposition. Interestingly,the laminar flame speeds exhibited a lack of sensitivityto the ethanol decomposition reactions even at fuel-rich conditions, although flame-speed sensitivity in-creased within the ethylene/vinyl submechanism as re-flected by C2H3 1 H 4 C2H2 1 H2, C2H2 1 H(1M)4 C2H3(1M) and C2H3 1 O2 4 CH2HCO 1 O.This is due to the C H OH(1M) 4 C H 1 H O2 5 2 4 2

(1M) reaction.



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Figure 20 Normalized first order sensitivity coefficients of the most important reactions on themass burning rate of lean, near-stoichiometric and rich ethanol/air flames at P 5u

1.0 atm and T 5 453 K.u

Modeling Species Concentrations from aJet-Stirred Reactor

Aboussi [64] performed ethanol oxidation measure-ments in an atmospheric jet-stirred reactor. The ex-perimental conditions covered the 1000–1200 K tem-perature range, and equivalence ratios of 0.2–2.0 at afixed ethanol concentration of 0.3%. Measurementswere taken as a function of residence time for CO,CO2, CH4, C2H4, C2H6, CH3HCO, and C2H5OH. TheAboussi data set was reported later by Dagaut and co-workers in their ethanol oxidation modeling study [7].Fair agreement was achieved between the jet-stirredreactor data and the Dagaut numerical calculations.However, their model overpredicted the ethylene andethane concentrations, and underpredicted carbon di-oxide.

The ethanol oxidation experimental data of Aboussiwas used to validate the current chemical kineticmodel by comparing the predicted stable species pro-files to those measured in the jet-stirred reactor. Thenumerical computations were performed at f 5 1.0and f 5 2.0, and the results are shown in Figures 21–24.

In Figure 21, a comparison of the f 5 1.0 experi-mental data against the numerically computed speciesconcentrations on a mole fraction basis is shown for

The modeling resultsC H OH, C H , CO, and CO .2 5 2 4 2

show relatively good agreement with the species con-centrations as the mean residence time was varied. Thecalculated profiles for the reaction intermediates of

(FormicCH HCO, C H , CH , CH O, and HCOOH3 2 6 4 2

Acid) are shown in Figure 22. The modeling results

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Figure 21 Ethanol9O29N2 (0.3%–0.9%–98.8%) oxi-dation in a Jet-Stirred Reactor at F 5 1.0, 1.0 atmosphere,and a nominal temperature of 1056 K. Measurements andPredictions for C H OH, C H , CO and CO .2 5 2 4 2

Figure 22 Ethanol9O29N2 (0.3%–0.9%–98.8%) oxi-dation in a Jet-Stirred Reactor at F 5 1.0, 1.0 atmosphere,and a nominal temperature of 1056 K. Measurements andPredictions for CH4, CH3HCO, and C2H6. Additional Pre-dictions shown for Formic Acid (HCOOH) and CH2O.

Figure 23 Ethanol9O29H2 (0.3%–0.45%–99.25%)oxidation in a Jet-Stirred Reactor at F 5 2.0, 1.0 atmo-sphere, and a nominal temperature of 1070 K. Measurementsand Predictions for C2H5OH, C2H4, CO and CO2.

Figure 24 Ethanol9O29N2 (0.3%–0.45%–99.25%)oxidation in a Jet-Stirred Reactor at F 5 2.0, 1.0 atmo-sphere, and a nominal temperature of 1070 K. Measurementsand Predictions for CH4, CH3HCO, and C2H6. AdditionalPredictions shown for Formic Acid (HCOOH) and CH2O.

show a fairly good representation of the CH3HCO andC2H6 measurements. The CH2O and HCOOH (FormicAcid) computed profiles are shown as well, althoughthese compounds were not measured in the jet-stirredreactor study. Formaldehyde is predicted to be formedin abundance, while HCOOH is predicted in smallquantities.

Reaction flux analysis was performed at f 5 1.0to determine the important ethanol consumption routesand the important production routes for the many re-action intermediates formed. Approximately 47% ofthe ethanol consumption flux was controlled by

whereC H OH 1 OH 4 Products C H OH 12 5 2 5

was the dominating ethanolOH 4 CH CH O 1 H O3 2 2

consumption reaction at 26%. The overallreaction consumed 22% ofC H OH 1 H 4 Products2 5

the ethanol where C2H5OH 1 H 4 CH3CHOH 1 H2

contributed 12% toward ethanol consumption. TheC2H5OH 1 O 4 Products, C2H5OH 1 CH3 4 Prod-ucts, and C2H5OH(1M) 4 C2H4 1 H2O(1M) reac-tions consumed 11%, 9%, and 8% of the ethanol, re-spectively. Acetaldehyde (CH3HCO) is primarily(70%) formed through the reaction sequences ofC2H5OH 1 OH 4 CH3CHOH 1 H2O (34%), and

(33%), followedC H OH 1 H 4 CH CHOH 1 H2 5 3 2

by CH3CHOH 1 O2 4 CH3HCO 1 HO2, with theremainder (30%) from C2H5OH 1 OH 4 CH3CH2O1 H2O and CH3CH2O 1 M 4 CH3HCO 1 H 1 M.Methane formation involves several participating re-actions such as CH 1 HO 4 CH 1 O (27%),3 2 4 2

(14%),CH 1 H 4 CH 1 H CH HCO 1 CH 43 2 4 3 3

(15%),CH CO 1 CH C H OH 1 CH 43 4 2 5 3

(10%), andC H OH 1 CH C H OH 1 CH 42 4 4 2 5 3

(19%). Ethane is formed exclu-CH CHOH 1 CH3 4

sively by CH3 1 CH3(1M) 4 C2H6(1M). The methylradical is a necessary precursor species to methane andethane formation and evolves primarily fromCH3CH2O 1 M 4 CH3 1 CH2O 1 M (33%),CH3CO(1M) 4 CH3 1 CO(1M) (21%), and to asmaller extent, CH2HCO 4 CH3 1 CO (11%), CH4

1 OH 4 CH3 1 H2O (10%), CH3HCO 1 OH 4 CH3

1 HCOOH (8%), and CH2CO 1 H 4 CH3 1 CO(8%). Carbon monoxide is principally produced from

(34%) andHCO 1 M 4 H 1 CO 1 M HCO 1and secondarily byO 4 CO 1 HO (28%),2 2

CH3CO(1M) 4 CH3 1 CO(1M) (14%). Carbon di-oxide production was controlled by the following re-actions in order of importance: HCCO 1 O2 4 CO2

1 HCO (37%), CO 1 OH 4 CO2 1 H (36%), andCO 1 HO2 4 CO2 1 OH (17%). Ethylene is formedby two principal pathways. The reaction sequence of

andC H OH 1 OH 4 C H OH 1 H O C H OH 42 5 2 4 2 2 4

contributes about 55% to ethylene produc-C H OH2 4

tion, and the remainder is due to the eth-

anol dehydration step, C H OH(1M) 4 C H 12 5 2 4

(27%), and the reaction sequencesH O(1M)2

andC H OH(1M) 4 C H 1 OH(1M) C H2 5 2 5 2 5

(4%). Formaldehyde was(1M) 4 C H 1 H(1M)2 4

predicted to be principally formed from the reactionsequence of H2OC H OH 1 OH 4 CH CH O 12 5 3 2

and CH3CH2O 1 M 4 CH3 1 CH2O 1 M (43%),and followed byCH 1 HO 4 CH O 1 OH3 2 3

(34%). Formic acidCH O(1M) 4 CH O 1 H(1M)3 2

(HCOOH) was predicted to be exclusively producedfrom acetaldehyde by the CH HCO 1 OH 43

reaction.CH 1 HCOOH3

The ethylene formation pathways deserve furthercomment as previous modeling studies by Norton andDryer, and Dagaut and co-workers had easily pre-dicted their respective ethylene profiles without thecontribution from the ethanol dehydration reaction.The modeling studies from these research groups had

andC H OH 1 OH 4 C H OH 1 H O C H OH 42 5 2 4 2 2 4

as the primary reaction sequence leadingC H 1 OH2 4

to ethylene production. Dagaut overpredicted theethylene concentration while using a branchingratio value of about 0.40 at 1070 K for

Nortonk /k .C H OH1OH 4 C H OH 1 H O C H OH1OH 4 Products2 5 2 4 2 2 5

and Dryer used a branching value of 0.30 around 1100K to model the ethylene concentrations seen in theirturbulent flow reactor. Earlier in this study we hadpresented an empirical approach for predicting thebranching ratio variation with temperature. A branch-ing ratio value of approximately 0.17 was obtainedaround 1100 K for ask /kC H OH1OH 4 C H OH1H O overall2 5 2 4 2

discussed earlier. This value is lower than the valuesused in the previous modeling studies, and thereforethe reaction sequence of C2H5OH 1 OH 4 C2H4OH1 H2O and C2H4OH 4 C2H4 1 OH could not accountfor all the ethylene seen in the Aboussi experimentsas well as the Norton and Dryer ethylene measure-ments in their turbulent flow reactor. The ethanol de-hydration reaction was added to the detailed chemicalkinetic model in order to overcome this problem. Thecombined effort of detailed chemical kinetic modelingand using RRKM/Master Equation theory forC2H5OH(1M) 4 C2H4 1 H2O(1M) and

rate constantC H OH(1M) 4 C H 1 OH(1M)2 5 2 5

calculations were necessary in matching the ethyleneprofiles shown in this study.

In Figures 23 and 24, a comparison of the f 5 2.0experimental data against the numerically computedspecies concentrations on a mole fraction basis isshown for C2H5OH, C2H4, CO, CO2, CH3HCO, C2H6,and CH4. The modeling results show relatively goodagreement with the species concentrations, as themean residence time varied, although the CH4 concen-tration was overpredicted. The calculated profiles for



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the reaction intermediates of HCOOH, and CH2O arealso shown in Figure 24. Reaction flux analysis indi-cated that approximately 36% of the ethanol con-sumption flux is controlled by C H OH 1 OH 42 5

followed by atProducts C H OH 1 H 4 Products2 5

26%, at 16%,C H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

and at 10%. TheC H OH 1 CH 4 Products2 5 3

CH3HCO, C2H6, C2H4, CH4, CH2O, HCOOH, and COreaction intermediates are produced by the same re-action sequences as discussed for the f 5 1.0 case.However, the f 5 2.0 case indicates that 45% of theethylene is primarily produced by C2H5OH(1M) 4C2H4 1 H2O(1M); the remainder is due to C2H5OH1 OH 4 C2H4OH 1 H2O and C2H5OH 1 H 4C2H4OH 1 H2, followed by C H OH 4 C H 12 4 2 4

and C2H5OH(1M) 4 C2H5 1 OH(1M),OH at 42%;followed by C2H5(1M) 4 C2H4 1 H(1M) at 11%.

A sensitivity analysis study was conducted for thepurposes of determining the most sensitive reactionsthat strongly influence the overall rate of ethanol ox-idation at stoichiometric and rich conditions. Figures25 and 26 show the normalized sensitivity coefficientsimportant to ethanol consumption for the f 5 1.0 andf 5 2.0 cases. If the sensitivity coefficient exhibits apositive value or (p), that would indicate a decreasein the overall reactivity of the ethanol oxidation sys-tem, and a negative value or (q) would imply an in-crease in the overall reactivity of the ethanol oxidationsystem. For the conditions found in the Aboussi ex-periments, the six most sensitive reactions to the over-all rate of ethanol oxidation at stoichiometric and richconditions, in order of their peak sensitivity coeffi-cients, are

(q) H 1 O ;: OH 1 O (22)2

(q) CH 1 HO ;: CH O 1 OH (27)3 2 3

(p) CH 1 HO ;: CH 1 O (28)3 2 4 2

(p) CH CH O 1 M ;:3 2

CH 1 CH O 1 M (150)3 2

(p) H 1 HO ;: H 1 O (7)2 2 2

(q) CH CH O 1 M ;:3 2

CH CHO 1 H 1 M (149)3

The H 1 O2 4 OH 1 O chain branching reactionexhibits a large negative sensitivity coefficient that in-creases with mean residence time. This is caused byadditional fuel consumption which allows for greaterH-atom generation at longer residence times. The H-atom sources are HCO 1 M 4 H 1 CO 1 M,CH3CH2O 1 M 4 CH3HCO 1 H 1 M, CH2HCO 1M 4 CH2CO 1 H 1 M, CH3O 1 M 4 CH2O 1 H1 M, and OH 1 H2 4 H2O 1 H.

The decomposition reactions exhibitedCH CH O3 2

a large positive and negative sensitivity coefficient, asshown in Figures 25 and 26. The branching ratio forCH3CH2O decomposition to CH3HCO 1 H and CH3

1 CH2O products was largely determined by matchingthe measured CH3HCO, CH4, and profiles inC H OH2 5

the jet-stirred and turbulent flow reactor modelingstudy. The rate constant assigned to each reaction wasverified by performing a QRRK analysis on the CH3

1 CH2O 4 CH3CH2O 4 CH3HCO 1 H reaction net-work, and the results are shown for 1.0 atm in TableI. Interestingly, reaction flux analysis indicates

as one of theC H OH 1 OH 4 CH CH O 1 H O2 5 3 2 2

most important ethanol consuming reactions yet thisreaction does not appear as a very sensitive reactionto the overall ethanol oxidation rate. This finding is alittle misleading in that the sensitivity exhibited by

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Figure 25 Sensitivity Results for Ethanol9O29N2 oxi-dation in a Jet-Stirred Reactor for F 5 1.0 case.

Figure 26 Sensitivity Results for Ethanol9O29N2 oxi-dation in a Jet-Stirred Reactor for F 5 2.0 case.

is largely due to the rad-C H OH 1 OH 4 Products2 5

ical it produces. In the case of C H OH 1 OH 42 5

the CH3CH2O radical decomposesCH CH O 1 H O,3 2 2

to either products.CH HCO 1 H or CH 1 CH O3 3 2

Each pathway negates the other on their respective af-fect on the overall ethanol oxidation rate. This wouldexplain why the C H OH 1 OH 4 CH CH O 12 5 3 2

reaction does not appear to be sensitive. It mustH O2

be emphasized that the branching ratios selected forare important in deter-C H OH 1 OH 4 Products2 5

mining the correct product profiles found in the etha-nol oxidation jet-stirred and flow reactor studies aswell as obtaining the correct overall reactivity exhib-ited within the chemical system.

The sensitivity analysis results also show the im-portant influence the HO2 radical has on the overallethanol oxidation rate. Chain terminating reactionslike CH3 1 HO2 4 CH4 1 O2 and H 1 HO2 4H2 1 O2 tend to retard the ethanol oxidation processas they limit radical pool growth. Chain propagatingreactions like (followedCH 1 HO 4 CH O 1 OH3 2 3

by andCH O 1 M 4 CH O 1 H 1 M) H 13 2

tend to increase the rate of ethanolHO 4 OH 1 OH2

oxidation as these reactions convert the unreactiveHO2 radical to a reactive OH radical. The

reaction isC H OH 1 HO 4 CH CHOH 1 H O2 5 2 3 2 2

shown to be a sensitive reaction at short mean resi-dence times, although reaction flux analysis indicatesthat this reaction contributes no more than 2.0% of theethanol consumption flux. The limited amount of eth-anol conversion at the short residence times favorsHO2 production and the chain branching that occursthrough H2O2 decomposition. This is explained by thereaction sequence of C2H5OH 1 HO2 4 CH3CHOH 1H2O2, CH3CHOH 1 O2 4 CH3HCO 1 HO2 followedby H O 1 M 4 OH 1 OH 1 M.2 2

The reactionC H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

exhibits greater sensitivity with increasing equivalenceratio and is shown to be a very sensitive reaction at f5 2.0. Reaction flux analysis shows the ethanol de-hydration process commands a greater fraction of theethanol consumption flux at progressively rich con-ditions. This finding supports the sensitivity analysisresults.

Modeling Species Concentrations from aFlow Reactor

Norton and Dryer [6,13] performed an experimentaland modeling study of ethanol oxidation kinetics in aturbulent flow reactor. They reported experimentalprofiles of the stable species concentrations and tem-peratures for ethanol oxidation at atmospheric pres-

sure, initial temperatures near 1100 K, and the equiv-alence ratio range of 0.61–1.24. They foundacetaldehyde, ethylene and methane in nearly equalconcentrations as the major reaction intermediates pro-duced for the experimental conditions examined. Theirchemical kinetic modeling results showed very goodagreement with the experimental data, and they notedthe importance of selecting the proper branching ratiosfor reactions involving ethanol with OH and H-atom.

The experimental data of Norton and Dryer wereused to validate the current chemical kinetic model bycomparing the predicted stable species profiles tothose measured during the ethanol oxidation process.The numerical computations were performed at f 50.61 and f 5 1.24, and the results are shown in Fig-ures 27–31.

In Figures 27 and 28, a comparison of the experi-mental data against the numerically computed speciesconcentrations on a mole percent basis is shown for

Due to the un-C H OH, O , CO, CO , H , and H O.2 5 2 2 2 2

certainty in the experimental induction time, the nu-merical results had to be “time shifted” [6] to matchthe experimental data at the 50% fuel decay point. Theamount of the shift was approximately 24 millisecondsfor f 5 0.61 and 23 milliseconds for f 5 1.24. Theresults show relatively good agreement. The modelwas unable to reproduce the ethanol consumption pro-file for the f 5 0.61 case. The difference in the initialslope of the ethanol profile may be due to the reporteduncertainty in the measured temperature profile that



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Figure 27 Comparison between experimental (symbols)flow reactor oxidation data for f 5 0.61 as investigated byNorton and Dryer [6] and the numerical calculations (lines)using the detailed chemical kinetic model. The numericalresults were time “shifted” by ca. 224 msec. Experimentalconditions: 5.65% C2H5OH, 2.786% O2, and 96.649% Ni-trogen, Reynolds Number 5 7140, P 5 1 atm., and Tin 51092 K. Numerical simulations shown for C2H5OH, O2, CO,CO2, H2, and H2O.

was estimated to be 610 K. The O2, H2, H2O, and CO2

species were shown to be fairly well predicted, and theCO profile was reasonably predicted. The calculatedprofiles for the reaction intermediates, CH4, C2H2,C2H4, C2H6, CH3HCO, and C3H6 are shown in Figures29–31. The numerical results show a fair representa-tion of the CH3HCO, C2H6, C2H4, C2H2, and C3H6 pro-files, although additional modeling effort would ulti-

mately yield better agreement than shown in thefigures.

Reaction flux analysis was performed to determinethe important ethanol consumption and productionroutes for the many reaction intermediates formed.Ethanol is primarily consumed by C2H5OH 1 OH 4Products and secondarily by C H OH 1 O 42 5

and at the leanProducts C H OH 1 H 4 Products2 5

conditions of the turbulent flow reactor. Acetaldehydewas primarily produced through the reaction sequence

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Figure 28 Comparison between experimental (symbols)flow reactor oxidation data for f 5 1.24 as investigated byNorton and Dryer [6] and the numerical calculations (lines)using the detailed chemical kinetic model. The numericalresults were time “shifted” by ca.223 msec. Experimentalconditions: 5.81% C2H5OH, 1.407% O2, and 98.012% Ni-trogen, Reynolds Number 5 4900, P 5 1atm, and Tin 51100 K. Numerical simulations shown for C2H5OH, O2, CO,CO2, H2, and H2O.

Figure 29 Comparison between experimental (symbols)flow reactor oxidation data for f 5 0.61 as investigated byNorton and Dryer [6] and the numerical calculations (lines)using the detailed chemical kinetic model. The numericalresults were time “shifted” by ca. 224 msec. Experimentalconditions: 5.65% C2H5OH, 2.78% O2, and 96.649% Nitro-gen, Reynolds Number 5 7140, P 5 1 atm, and Tin 5 1092K. Numerical simulations shown for CH3HCO, C2H4, CH4,C2H6, and C2H2.

Figure 30 Comparison between experimental (symbols)flow reactor oxidation data for f 5 1.24 as investigated byNorton and Dryer [6] and the numerical calculations (lines)using the detailed chemical kinetic model. The numericalresults were time “shifted” by ca. 223 msec. Experimentalconditions: 5.81% C2H5OH, 1.407% O2, and 98.012% Ni-trogen, Reynolds Number 5 4900, P 5 1 atm, and Tin 51100 K. Numerical simulations shown for CH3HCO, C2H4,CH4, C2H6, and C2H2.

Figure 31 Comparison between experimental (symbols)flow reactor oxidation data for f 5 0.61 and f 5 1.24 asinvestigated by Norton and Dryer [6] and the numerical cal-culations (lines) using the detailed chemical kinetic model.Numerical simulation shown for C3H6 (propene).

of followedC H OH 1 OH 4 CH CHOH 1 H O2 5 3 2

by and sec-CH CHOH 1 O 4 CH HCO 1 HO ,3 2 3 2

ondarily by C H OH 1 OH 4 CH CH O 1 H O2 5 3 2 2

and Meth-CH CH O 1 M 4 CH HCO 1 H 1 M.3 2 3

ane formation is primarily controlled by 1CH3

HO2 4 CH4 1 O2, C2H5OH 1 CH3 4 CH3CHOH 1CH4, and CH3HCO 1 CH3 4 CH3 CO 1 CH4.Ethane was formed exclusively by CH 1 CH3 3

(1M) 4 C2H6(1M). Ethylene was produced by thereaction sequence of C H OH 1 OH 4 C H OH 12 5 2 4

and followedH O C H OH 1 H 4 C H OH 1 H2 2 5 2 4 2

by ethanol dehydration, andC H OH 4 C H 1 OH,2 4 2 4

followed byC H OH(1M) 4 C H 1 OH(1M)2 5 2 5

Acetylene was pro-C H (1M) 4 C H 1 H(1M).2 5 2 4

duced by way of the ethylene intermediate compound.The reaction sequence of C H 1 OH 4 C H 12 4 2 3

metathesis to andH O, C H 1 O C H 1 HO ,2 2 3 2 2 2 2

contributed to theC H (1M) 4 C H 1 H(1M)2 3 2 2

acetylene formation as measured in the experiment.Lastly, propene (C3H6) was formed by the vinyl(C2H3) and methyl (CH3) radical combination reac-tion.

A sensitivity analysis study was conducted for thepurpose of determining the most sensitive reactionsthat strongly influence the overall rate of ethanol ox-idation. The analysis was performed by perturbing theforward and reverse rate constants for each reactionby a factor of two, thereby leaving the thermochem-istry or thermodynamic equilibrium constant withinthe chemical reaction unaffected. The sensitivity co-efficient was then determined by taking the naturallogarithm of the mole fraction of ethanol remainingafter 25 milliseconds of computed oxidation time with

the perturbed reaction kinetics divided by the baselinemole fraction of ethanol. The sensitivity coefficient isexpressed as If theS 5 2ln(X X ).C H OH,pert C H OH,unpert2 5 2 5

sensitivity coefficient exhibits a negative value thatwould indicate a decrease in the overall reactivity ofthe chemical system, and a positive value would implyan increase in the overall reactivity of the chemicalsystem. Figure 32 shows the results of the sensitivityanalysis performed for the f 5 0.61 case. The H 1

reaction is shown to be the most sen-O 4 OH 1 O2

sitive reaction to the overall rate of ethanol oxidationat lean conditions, followed by CH 1 HO 43 2

CH3O 1 OH, CH3 1 HO2 4 CH4 1 O2, CH3CH2Odecomposition to CH3 1 CH2O and CH3HCO 1H, C2H5OH 1 HO2 4 CH3CHOH 1 H2O2, and

TheC H OH(1M) 4 CH 1 CH OH(1M). H 12 5 3 2

chain branching reaction affects theO 4 OH 1 O2

OH and O-atom radical pool, as noted by the largepositive sensitivity coefficient. These reactive radicalsare important to consuming ethanol. The CH 13

reaction enhances the ethanolHO 4 CH O 1 OH2 3

oxidation rate and this is largely due to the conversionof two unreactive radicals (i.e., CH3, HO2) to two re-active radicals (i.e., OH, H) through the reaction se-quence of followed byCH 1 HO 4 CH O 1 OH3 2 3

TheCH O(1M) 4 CH O 1 H(1M). CH 13 2 3

shows a negative sensitivity coef-HO 4 CH 1 O2 4 2

ficient due to the chain terminating nature of the re-action. The CH CH O 1 M 4 CH 1 CH O 1 M3 2 3 2

and decom-CH CH O 1 M 4 CH HCO 1 H 1 M3 2 3

position reactions exhibit opposing sensitivity coeffi-cient values. This result shows the role H-atom andCH3 radicals play in increasing or decreasing the eth-



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Figure 32 First order sensitivity coefficients of the important reactions affecting the ethanol con-sumption rate. See text for discussion. Experimental conditions: 5.65% C2H5OH, 2.786% O2, and96.649% Nitrogen, Reynolds Number 5 7140, P 5 1atm, and Tin 5 1092 K.

anol consumption rate by its impact on the radicalpool. The C H OH 1 HO 4 CH CHOH 1 H O2 5 2 3 2 2

reaction has a fairly large positive sensitivity coeffi-cient at lean conditions as the conversion of HO2 toH2O2 can lead to OH radical production by H O2 2

(1M) 4 OH 1 OH(1M). However, C H OH 12 5

does not contribute sig-HO 4 CH CHOH 1 H O2 3 2 2

nificantly to the ethanol consumption flux in spite ofthe sensitivity analysis results. The C H OH 12 5

reactions exhibit small sensitivity co-OH 4 Productsefficients, although ethanol consumption by OH radi-cals is very important to ethanol oxidation. The posi-tive sensitivity coefficients shown for C H OH2 5

(1M) 4 C2H4 1 H2O(1M) and C H OH(1M) 42 5

reflect the importance of etha-CH 1 CH OH(1M)3 2

nol decomposition at these conditions.

SUMMARY

A chemical kinetic modeling investigation was pre-sented which successfully reproduced the measure-ments from five different experimental systems. Themodeling study of ignition delay in shock tubes notedthe importance of the C2H5OH(1M) 4 CH3 1CH2OH(1M), C2H5OH(1M) 4 C2H5 1 OH(1M)and O 1 OH 4 O2 1 H reactions. Ignition delay timeswere successfully reproduced when representing theethanol decomposition reactions as pseudo-first orderrate expressions using the Troe format for fall-off ki-netics. The modeling study of laminar flame speeds infreely propagating flames showed that proper charac-terization of the H-atom production and consumptionsteps, and HCO and CO oxidation kinetics are veryimportant for proper ethanol-air flame speed predic-tion. Jet-stirred and turbulent flow reactor modeling ofethanol oxidation showed the importance of the

reaction and its branch-C H OH 1 OH 4 Products2 5

ing ratio selection, and the reaction kinetics forover a wideC H OH(1M) 4 C H 1 H O(1M)2 5 2 4 2

range of equivalence ratios. Sensitivity analysisshowed at all equivalence ratios the relative impor-tance of the H 1 O2 chain branching reaction;

decomposi-C H OH 1 OH 4 Products; CH CH O2 5 3 2

tion to products;CH 1 CH O and CH HCO 1 H3 2 3

and HO2 reactions with CH3, H-atom, and ethanol.Lastly, an empirical procedure was used to derive thebranching ratios for C H OH 1 OH, C H OH 1 O,2 5 2 5

and reactions that wasC H OH 1 H, C H OH 1 CH2 5 2 5 3

instrumental to the success of the high temperatureethanol oxidation model validation study.

The modeling work was performed under the auspices of theU.S. Department of Energy by the Lawrence Livermore Na-tional Laboratory under contract No. W-7405-ENG-48.

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