Experimental and modeling study of the pyrolysis and combustion of dimethoxymethane

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Frédérique Battin-Leclerc, Guy B. Marin and Kevin M.

1 Experimental and modeling study of the pyrolysis and combustion of dimethoxymethane Florence Vermeire, Hans-Heinrich Carstensen, Olivier Herbinet, Frédérique Battin-Leclerc, Guy B. Marin and Kevin M. Van Geem Laboratory for Chemical Technology, Ghent University ICCK 2017, Chicago, 05/23/2017 1

High O:C ratio Better physical properties Objectives: Acquire experimental dataset in an isothermal jet-stirred

2 Dimethoxymethane as fuel additive CO Unburned HC Biodiesel Bio-ethanol Dimethylether Diesel engine Particulate matter NO x High O:C ratio Physical properties not good for common engines Oxymethylene ethers n = 1 n = 2 n = 3 High O:C ratio Better physical properties Objectives: Acquire experimental dataset in an isothermal jet-stirred reactor Develop a first principles based microkinetic model for the oxidation and pyrolysis of dimethoxymethane (DMM) 2

3 Outline of talk Experimental setup Kinetic modeling Potential energy surface Model performance Rate of production analysis Conclusion 3

Jet-stirred reactor set-up Operating conditions x fuel,0 = 0.01 ϕ = 0.25, 1.0, 2.0, P = 0.

4 Jet-stirred reactor set-up Operating conditions x fuel,0 = 0.01 ϕ = 0.25, 1.0, 2.0, P = MPa T = K F V,0 = m³/s Diluent: He Calibration (relative error %) 1. Injection of known amount (5%) 2. Effective carbon number method (10%) 22 product species identified and quantified Elemental C balance close within 5 % for most conditions Herbinet, O., and F. Battin-Leclerc , International Journal of Chemical Kinetics, 46:

5 Outline of talk Experimental setup Kinetic modeling Potential energy surface Model performance Rate of production analysis Conclusion 5

Kinetic model development Genesys Automatic kinetic model generation 351 species 2904 reactions Extensive databases with quantum mechanical calculations at the CBS-QB3 level of theory Thermodynamic

6 Kinetic model development Genesys Automatic kinetic model generation 351 species 2904 reactions Extensive databases with quantum mechanical calculations at the CBS-QB3 level of theory Thermodynamic databases Kinetic databases Extended for DMM pyrolysis and oxidation Base mechanism AramcoMech 1.3. Smallest species and reactions during combustion Metcalfe, W. K., S. M. Burke, S. S. Ahmed, and H. J. Curran "A Hierarchical and Comparative Kinetic Modeling Study of C-1 - C-2 Hydrocarbon and Oxygenated Fuels." International Journal of Chemical Kinetics 45 (10): Reactant input 1. Inchi 2. SMILES InChI=1S/C3H8O2/c /h3H2,1-2H3 COCOC Reaction family input 1. Low temperature reactions 2. High temperature reactions Kinetic and thermodynamic databases 1. CBS-QB3 species and reactions 2. Structure related rules 6

7 Outline of talk Experimental setup Kinetic modeling Potential energy surface Model performance Rate of production analysis Conclusion 7

8 C 3 H 7 O 2 potential energy surface Formaldehyde and methyl formate main product species Note: difference in barrier height for β-scission reactions T = 700 K k β-sc,1 = s -1 k β-sc,2 = s -1 Life-time of secondary radical short because of fast β-scission, no addition of molecular oxygen 8

C 3 H 7 O 4 potential energy surface 3 isomerizations Transition state can have 4-ring, 6-ring or 8-ring Isomerization T = 700 K with aldehyde T = formation 700 K, alkanes Cyclic k isom,4-ring ether

9 C 3 H 7 O 4 potential energy surface 3 isomerizations Transition state can have 4-ring, 6-ring or 8-ring Isomerization T = 700 K with aldehyde T = formation 700 K, alkanes Cyclic k isom,4-ring ether = formation s -1 k isom,4-ring = s -1 β-scission k isom,6-ring = s -1 k isom,6-ring = s -1 Subsequent k isom,8-ring = chain branching 5 s -1 (Bugler et al. 2015) T = 700 K k 1,Htr ,Htr = s -1 k 1,CE ,CE = s -1 k 1,β-sc ,β-sc = s -1 k 1,β-sc2 = s -1 T = 700 K, alkanes k 1,CE 6.8 2,CE = s -1 k 1,β-sc = s -1 (Bugler et al. 2015) 9

10 2 nd addition of molecular oxygen Potential energy surfaces for: 4 isomerizations Transitions state can have 4-ring, 6-ring or 8-ring T = 700 K k isomkp3,4-ring = s -1 k isomkp1,6-ring = s -1 k isom,6-ring = s -1 k isomoo,8-ring = s -1 10

11 Outline of talk Experimental setup Kinetic modeling Potential energy surface Model performance Rate of production analysis Conclusion 11

12 Model performance for DMM pyrolysis Burke mechanism S.M. Burke, W. Metcalfe, O. Herbinet, F. Battin- Leclerc, F.M. Haas, J. Santner, F.L. Dryer, H.J. Curran, Combustion and Flame, 161 (2014) Aramco 1.3 mechanism W.K. Metcalfe, S.M. Burke, S.S. Ahmed, H.J. Curran, International Journal of Chemical Kinetics, 45 (2013)

13 Model performance for DMM oxidation (1) Simulations with CHEMKIN PRO using a CSTR x fuel,0 = 0.01 P = Mpa T = K F V,0 = m³/s Model performance for low temperature oxidation can be improved, see formaldehyde mole fraction ϕ=2.0 ϕ=1.0 ϕ=

14 Model performance for DMM oxidation (2) Simulations with CHEMKIN PRO using a CSTR x fuel,0 = 0.01 P = Mpa T = K F V,0 = m³/s Model performance for low temperature oxidation can be improved, see methyl fomate mole fraction ϕ=2.0 ϕ=1.0 Hydrocarbon mole fractions overpredicted by the micro kinetic model ϕ=

15 Outline of talk Experimental setup Kinetic modeling Potential energy surface Model performance Rate of production analysis Conclusion 15

16 Rate of production analysis with CHEMKIN PRO. Rate of production relative to DMM Pathways at low temperatures x fuel,0 = 0.01 P = Mpa T = 650 K and 700 K F V,0 = m³/s ϕ = 1.0 Secondary radical only reacts through β-scission Primary radical competition between β-scission and oxygen addition 3 branching pathways CH 3 base mechanism 16

17 Conclusions New experimental dataset acquired for the pyrolysis and oxidation of dimethoxymethane in an isothermal jet-stirred reactor Development of a first-principles based microkinetic model for the pyrolysis and oxidation of dimethoxymethane with quantum mechanical calculations at the CBS-QB3 level of theory Using kinetics developed for alkanes to describe the pyrolysis and oxidation of dimethoxymethane introduces large errors Aramco 1.3 mechanism selected as base mechanism, because of better performance for pyrolysis Good model performance obtained for most compounds, prediction of low temperature reactivity and hydrocarbon mole fractions can be improved 17

18 Acknowledgements This work was supported by the Institute for promotion of Innovation through Science and Technology in Flanders (IWT) through the SBO project ARBOREF and the SMARTCATS STSM COST Action CM

19 Thank you 19

20 Back-up 20

21 Genesys reaction families and kinetics Reaction family Kinetic source* Hydrogen abstraction by H, -C, -O GAV (Paraskevas et al. 2014)(Paraskevas et al. 2015) Hydrogen abstraction by HO 2, HO, O 2, O β-scission & CO α-scission Homolytic scissions Similar to alkanes (Cai et al. 2016)(Sivaramakrishnan and Michael 2009) Well chosen similar reactions calculated at CBS-QB3 level of theory Similar to DME (Curran et al. 1998) and DEE (Yasunaga et al. 2010) O 2 addition Similar to alkanes (Cai et al. 2016) Isomerization after 1st and 2nd addition Cyclic ether formation Similar to alkanes (Bugler et al. 2015)(Cai et al. 2016)(Sharma, Raman, and Green 2010) Similar to alkanes (Bugler et al. 2015)(Cai et al. 2016)(Sharma, Raman, and Green 2010) R + RO 2 RO + RO R + HO 2 RO + HO R + CH 3 O 2 RO + CH 3 O ROOH RO + OH RO 2 + HO 2 ROOH + O 2 RO 2 + H 2 O 2 ROOH + HO 2 RO 2 + CH 3 O 2 RO + CH 3 O + O 2 RO 2 + RO 2 RO + RO + O 2 Similar to alkanes (Bugler et al. 2015)(Cai et al. 2016) * Kinetics applied if no data at CBS-QB3 level of theory is available in extensive database 21

22 Sensitivity analysis (1) Sensitivity analysis with CHEMKIN PRO. Normalized sensitivity coefficients x fuel,0 = 0.01 P = Mpa T = 900 K F V,0 = m³/s ϕ =

23 Sensitivity analysis (2) Sensitivity analysis with CHEMKIN PRO. Normalized sensitivity coefficients x fuel,0 = 0.01 P = Mpa T = 700 K F V,0 = m³/s ϕ =

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