High-temperature ethane and propane decomposition

Abstract The decomposition rates of ethane and propane in the falloff regime at high temperatures were studied in a shock tube using UV narrow-line laser absorption of CH 3 at 216.6 nm. Experimental conditions ranged from 1343 to 2034 K and 0.13 to 8.4 atm with mixtures varying in concentration from 100 to 402 ppm of ethane or propane diluted in argon. Decomposition rate coefficients were determined by monitoring the formation rate of CH 3 immediately behind shock waves and modeling the CH 3 formation with a detailed kinetic model. Calculations were performed using RRKM/master equation analysis with a restricted (hindered) Gorin model for the transition state and fit to the current high-temperature dissociation data as well as previous low-temperature recombination measurements. The decomposition rate coefficient for ethane decomposition from 700 to 1924 K can be described, using the Troe pressure broadening formulation, by k ∞, 1  ( T ) = 1.88 × 10 50 T −9.72 exp (−54,020 K/ T ) s −1 , k 0, 1  ( T ) = 3.72 × 10 65 T −13.14 exp (−51,120 K/ T ) cm 3  mol −1  s −1 , and F cent, 1  ( T ) = 0.61 exp (− T /100 K) + 0.39 exp (− T /1900 K) +  exp (−6000 K/ T ). The decomposition rate coefficient for propane decomposition from 600 to 1653 K can be described by k ∞, 2  ( T ) = 1.29 × 10 37 T −5.84 exp (−49,010 K/ T ) s −1 , k 0, 2  ( T ) = 5.64 × 10 74 T −15.74 exp (−49,680 K/ T ) cm 3  mol −1  s −1 , and F cent, 2  ( T ) = 0.69 exp (− T /50 K) + 0.31 exp (− T /3000 K) + exp (−9000 K/ T ).

[1]  P. Roth,et al.  Messungen zur Hochtemperaturpyrolyse von Äthan , 1979 .

[2]  R. Hanson,et al.  A study of ethane decomposition in a shock tube using laser absorption of CH3 , 1993 .

[3]  Jürgen Warnatz,et al.  The Mechanism of High Temperature Combustion of Propane and Butane , 1983 .

[4]  A. V. Knyazev,et al.  Kinetics of the Reactions of n-Alkyl (C2H5, n-C3H7, and n-C4H9) Radicals with CH3 , 2001 .

[5]  K. Kawaguchi,et al.  Diode laser study of the ν2 band of the methyl radical , 1981 .

[6]  H. Wagner,et al.  Recombination of CH3 radicals at elevated pressures and temperatures , 1991 .

[7]  J. Simmie,et al.  Falloff behavior in propane thermal decomposition at high temperature , 1982 .

[8]  Anthony M. Dean,et al.  Predictions of pressure and temperature effects upon radical addition and recombination reactions , 1985 .

[9]  W. Gardiner,et al.  Shock tube and modeling study of methyl radical in methane oxidation , 1987 .

[10]  Masao Suga,et al.  Thermal decomposition of ethane in shock waves , 1985 .

[11]  M. Pilling,et al.  Experimental and Theoretical Study of the Recombination Reaction CH3 + CH3 > C2H6. , 1991 .

[12]  W. D. Good,et al.  Thermodynamics of Organic Compounds. , 1980 .

[13]  H. Kawano,et al.  Thermal decomposition of propane in shock waves , 1989 .

[14]  W. Tsang Rate constants for the decomposition and formation of simple alkanes over extended temperature and pressure ranges , 1989 .

[15]  Ronald K. Hanson,et al.  REVISED VALUES FOR THE RATE COEFFICIENTS OF ETHANE AND METHANE DECOMPOSITION , 1995 .

[16]  J. Kiefer,et al.  The very‐high‐temperature pyrolysis of ethane: Evidence against high rates for dissociative recombination reactions of methyl radicals , 1984 .

[17]  G. B. Skinner,et al.  Resonance absorption measurements of atom concentrations in reacting gas mixtures 5. Pyrolysis of C3H8 and C3D8 behind shock waves , 1981 .

[18]  Takao Tsuboi,et al.  UV Absorption Study on the Reaction of Methyl Radicals behind Shock Waves , 1978 .

[19]  Ronald K. Hanson,et al.  A cw laser absorption diagnostic for methyl radicals , 1993 .

[20]  R. Hanson,et al.  An improved determination of the 216.615 nm absorption coefficient for methyl radicals , 1995 .

[21]  David R. Lide,et al.  Microwave Spectrum, Structure, and Dipole Moment of Propane , 1960 .

[22]  D. Golden,et al.  Relationship between bond dissociation energies and activation energies for bond scission reactions , 1994 .

[23]  T. Koike,et al.  Shock tube studies of the acetylene and ethylene pyrolysis by UV absorption. , 1981 .

[24]  C. W. Larson,et al.  Pressure and temperature dependence of reactions proceeding via a bound complex. 2. Application to 2CH3 → C2H5 + H , 1989 .

[25]  R. J. Kee,et al.  Chemkin-II : A Fortran Chemical Kinetics Package for the Analysis of Gas Phase Chemical Kinetics , 1991 .

[26]  Lawrence B. Harding,et al.  A Direct Transition State Theory Based Study of Methyl Radical Recombination Kinetics , 1999 .

[27]  P. H. Stewart,et al.  The pressure and temperature dependence of methane decomposition , 1989 .

[28]  R. C. Weast CRC Handbook of Chemistry and Physics , 1973 .

[29]  T. Tanzawa,et al.  Thermal decomposition of ethane , 1979 .

[30]  G. B. Skinner,et al.  High temperature decomposition of ethane , 1973 .

[31]  I. R. Slagle,et al.  Kinetics of the Reactions of Allyl and Propargyl Radicals with CH3 , 2001 .

[32]  M. Pilling,et al.  Application of the Canonical Flexible Transition State Theory to CH3, CF3, and CCl3 Recombination Reactions , 1998 .

[33]  W. Gardiner,et al.  Thermal decomposition of propane , 1980 .

[34]  J. Hessler,et al.  Recombination of Methyl Radicals. 2. Global Fits of the Rate Coefficient , 1996 .

[35]  John R. Barker,et al.  Multiple‐Well, multiple‐path unimolecular reaction systems. I. MultiWell computer program suite , 2001 .

[36]  Takehiko Shimanouchi,et al.  Tables of molecular vibrational frequencies. Consolidated volume II , 1972 .

[37]  Michael J. Pilling,et al.  Study of the recombination reaction methyl + methyl .fwdarw. ethane. 1. Experiment , 1988 .

[38]  J. Hessler,et al.  Recombination of Methyl Radicals. 1. New Data between 1175 and 1750 K in the Falloff Region , 1996 .

[39]  W. Goddard,et al.  Ab Initio Investigation of Ethane Dissociation Using Generalized Transition State Theory , 2001 .

[40]  C. Alcock,et al.  Thermodynamic Properties of Individual Substances , 1994 .

[41]  David M. Wardlaw,et al.  Study of the recombination reaction methyl + methyl .fwdarw. ethane. 2. Theory , 1988 .

[42]  J. Troe,et al.  Collisional deactivation of vibrationally highly excited polyatomic molecules. II. Direct observations for excited toluene , 1983 .

[43]  G. B. Skinner,et al.  RESONANCE ABSORPTION MEASUREMENTS OF ATOM CONCENTRATIONS IN REACTING GAS MIXTURES. 7. PYROLYSIS OF ETHANE AND ETHANE-D6 BEHIND SHOCK WAVES , 1982 .

[44]  J. Kiefer,et al.  Shock-tube study of propane pyrolysis. Rate of initial dissociation from 1400 to 2300 K , 1983 .

[45]  W. Tsang,et al.  Chemically and Thermally Activated Decomposition of Secondary Butyl Radical , 2000 .