J. Phys. Chem. 1996, 100, 4019-4025
4019
Kinetic Studies of Chlorine Atom Reactions Using the Turbulent Flow Tube Technique John V. Seeley,† John T. Jayne,‡ and Mario J. Molina* Department of Earth, Atmospheric and Planetary Sciences, and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 ReceiVed: August 30, 1995; In Final Form: NoVember 30, 1995X
The turbulent flow tube technique has been used to determine the reaction rate constants of chlorine atoms with nitrogen dioxide, methane, and ozone. The Cl + NO2 f ClNO2 reaction was studied at pressures between 50 and 250 Torr. The room temperature rate constant was determined to be (7.2 ( 0.4) × 10-31 cm6 molecule-2 s-1 with Ar as a third body. The Cl + CH4 f HCl + CH3 reaction was studied at temperatures between 181 and 291 K; the experimentally determined Arrhenius expression is given by k ) (7.0 ( 1.6) × 10-12 exp[-(1270 ( 60)/T] cm3 molecule-1 s-1. The Cl + O3 f ClO + O2 reaction was studied at temperatures between 206 and 296 K; the resulting Arrhenius expression is given by k ) (1.63 ( 0.34) × 10-11 exp[-(91 ( 61)/T] cm3 molecule-1 s-1. The stated uncertainties for the values of rate constants and Arrhenius parameters are reported at the one standard deviation level and represent only the precision of the data. In each case the experimentally determined rate constant is in good agreement with earlier results obtained by using flashphotolysis and conventional low-pressure discharge flow systems. This study demonstrates that the turbulent flow tube method is a viable technique for studying gas phase reaction kinetics over a wide range of temperatures and pressures.
Introduction The two most commonly used techniques for experimental studies of gas-phase reactions are flash photolysis and discharge flow. The relative strengths and weaknesses of these techniques have been reviewed by several authors.1-3 Flash photolysis systems can characterize reactions over a wide range of pressures and temperatures; however, the number of reactions which can be studied with this technique is limited because the labile reactant must have a photolytic precursor and it must be detectable on a rapid time scale (i.e., 264 K and (1.19 ( 0.20) exp(33/T) × 10-11 cm3 molecule-1 s-1 for T < 264 K. In Figure 7 we have also plotted the lines which Nicovich et al.38 used to fit their results and the line used by Zahniser et al.37 Rate Constant Ratio for the Cl + O3 and Cl + CH4 Reactions. DeMore carried out measurements of the relative
Figure 7. Rate constants for the Cl + O3 reaction. Error bars represent the mathematical precision of the data point at the two standard deviation level. The solid line is the fit to our experimental data, the line with the small dashes is based on the Arrhenius expression reported by Zahniser et al.,37 and the lines with large dashes are based on the Arrhenius expressions reported by Nicovich et al.38
rates of the Cl + O3 and Cl + CH4 reactions in the temperature range from 197 to 217 K,10 obtaining the rate constant ratios listed in Table 8. The table also gives the ratios estimated from our results, as well as from the NASA panel recommendation. Our ratios are in very good agreement with those measured by DeMore and in reasonable agreement with the NASA panel values. As discussed above, our measured values around 200 K for the two rate constants in question are larger by about 25% than the values given in the NASA recommendation; the ratio, however, turns out to be in good agreement. Conclusions Several conclusions can be drawn from our studies of Clatom reactions. The results from our investigation of the reaction of Cl + NO2 have shown that the turbulent flow tube technique can be used to accurately characterize the pressure dependence of a rate constant at pressures significantly larger than those accessible to the conventional discharge flow technique. The results from our investigation of the reaction of chlorine atoms with methane have shown that the turbulent flow tube technique can reproduce the results obtained with direct experimental techniques over the temperature range 200300 K. We have also been able to measure the rate constant of the Cl + CH4 reaction at temperatures as low as 181 K, thus extending the temperature range of direct flow tube rate constant measurements. These studies also indicate that the secondary reaction Cl + CH3 might interfere with an accurate determination of k2. The results from our investigations of the chlorine atom reactions with ozone agree well with the most recent studies of that reaction. Thus, we believe that the results of this work together with our previous studies6,17 demonstrate that the turbulent flow tube technique is a valid and versatile method for experimentally determining the rate constants of gas phase reactions over a broad range of pressures and temperatures.
TABLE 7: Summary of Previous Experimental Results for the Cl + O3 Reaction k3 ( σ at 298 K, 10-11 cm3 s-1
A ( σ, 10-11 cm3 s-1
E/R ( σ, K
temp range, K
1.33 ( 0.13 1.09 ( 0.02 1.16 ( 0.03 1.30 ( 0.07 1.14 ( 0.03
5.18 2.94 ( 0.49 3.08 ( 0.30 2.35 ( 0.50 2.49 ( 0.38, 1.19 ( 0.20 2.9 1.59 ( 0.31
418 ( 28 298 ( 39 290 ( 30 171 ( 30 233 ( 46, 33 ( 37 260 ( 100 87 ( 57
221-629 213-298 220-350 210-360 264-385, 189-263
1.2 1.21 ( 0.13
206-296
method
ref
flow tube flash photolysis flash photolysis flow tube flash photolysis
Clyne and Nip35 Kurylo and Braun36 Watson et al.27 Zahniser et al.37 Nicovich et al.38
review evaluation turbulent flow
NASA panel15 this work
Kinetic Studies of Chlorine Atom Reactions
J. Phys. Chem., Vol. 100, No. 10, 1996 4025
TABLE 8: Comparison of Values of the Ratio k3/k2 T, K
k3/k2 this work
k3/k2 DeMore10
k3/k2 NASA panel15
217 197
531 925
569 959
504 859
Acknowledgment. This research was supported by a grant from the NASA Upper Atmospheric Research Program to the Massachusetts Institute of Technology. We would also like to thank J. G. Anderson’s research group for supplying us with the chlorine resonance fluorescence lamps. John T. Jayne was supported by a postdoctoral fellowship funded by the Pew Foundation. References and Notes (1) Kaufman, F. Science 1985, 230, 392. (2) Howard, C. J. J. Phys. Chem. 1979, 83, 3. (3) Finlayson-Pitts, B. J.; Pitts, J. N. P. Atmospheric Chemistry; Wiley: New York, 1986. (4) Keyser, L. F. J. Phys. Chem. 1984, 88, 4750. (5) Abbatt, J. P. D.; Demerjian, K. L.; Anderson, J. G. J. Phys. Chem. 1990, 94, 4566. (6) Seeley, J. V.; Jayne, J. T.; Molina, M. J. Int. J. Chem. Kinet. 1993, 25, 571. (7) Patrick, R.; Golden, D. M. Int. J. Chem. Kinet. 1983, 15, 1189. (8) Kolb, C. E.; Jayne, J. T.; Worsnop, P. W.; Molina, M. J.; Meads, R. F.; Viggiano, A. A. J. Am. Chem. Soc. 1994, 116, 10314. (9) Seeley, J. V.; Meads, R. F.; Elrod, M. J.; Molina, M. J. J. Phys. Chem., submitted for publication. (10) DeMore, W. B. J. Geophys. Res. 1991, 96, 4995. (11) Prather, M. P.; Jaffe, A. H. J. Geophys. Res. 1990, 95, 3473. (12) Douglass, A. N.; Schoeberl, M. R.; Stolarski, R. S.; Waters, J. W.; Rusell, M. J.; Roche, A. E.; Massie, S. T. J. Geophys. Res. 1995, 100, 13967. (13) Schwab, J. J.; Anderson, J. G. J. Quant. Spectrosc. Radiat. Transfer. 1982, 27, 445. (14) Zahniser, M. S.; Chang, J S.; Kaufman, F. J. Chem. Phys. 1977, 67, 997. (15) DeMore, W. B.; Sander, S. P.; Howard, C. J.; Ravishankara, A. R.; Golden, D. M.; Kolb, C. E.; Hampson, R. F.; Kurylo, M. J.; Molina,
M. J. Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling. JPL Publication 94-26, 1994. (16) Fahien, R. W., Fundamentals of Transport Phenomena; McGrawHill: New York, 1983. (17) Seeley, J. V. Experimental Studies of Gas Phase Radical Reactions Using the Turbulent Flow Tube Technique. Ph.D. Thesis, MIT, 1994. (18) Seeley, J. V.; Molina, M. J. Manuscript in preparation. (19) Nelson, H. H.; Johnston, H. S. J. Phys. Chem. 1981, 85, 3891. (20) Clyne, M. A. A.; White, I. F. As reported by: Watson, R. T. J. Phys. Chem. Ref. Data 1977, 6, 871. And as reported by: Baulch, D. L.; Duxbury, J.; Grant, S. J.; Montague, D. C. J. Phys. Chem. Ref. Data 1981, 10, supplement 1. (21) Leu, M. T. Int. J. Chem. Kinet. 1984, 16, 1311. (22) Ravishankara, A. R.; Smith, G. J.; Davis, D. D. Int. J. Chem. Kinet. 1988, 20, 811. (23) Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J. J. Chem. Phys. 1978, 68, 5410. (24) Anastasi, C.; Smith, I. W. M. J. Chem. Soc. Faraday Trans. 2 1976, 72, 1459. (25) Keyser, L. F. J. Chem. Phys. 1978, 69, 214. (26) Timonen, R. S.; Gutman, D. J. Phys. Chem. 1986, 90, 2987. (27) Watson, R.; Machado, G.; Fischer, S.; Davis, D. D. J. Chem. Phys. 1976, 65, 2126. (28) Manning, R. G.; Kurylo, M. J. J. Phys. Chem. 1977, 81, 291. (29) Whytock, D. A.; Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J. J. Chem. Phys. 1977, 66, 2690. (30) Zahniser, M. S.; Berquist, B. M.; Kaufman, F. Int. J. Chem. Kinet. 1978, 10, 15. (31) Ravishankara, A. R.; Wine, P. H. J. Chem. Phys. 1980, 72, 25. (32) Tyndall, G. S.; Orlando, J. J.; Kegley-Owen, C. S. J. Chem. Soc., Faraday Trans. 1995, 91, 3055. (33) Nicovich, J. M.; Wang, S.; Wine, P. H. Private communication, 1995. (34) Timonen, R.; Kalliorinne, K.; Koskikallio, J. Acta Chem. Scand. 1986, A40, 459. (35) Clyne, M. A. A.; Nip, W. S. J. Chem. Soc. Far. Trans. 2 1976, 72, 838. (36) Kurylo, M. J.; Braun, W. Chem. Phys. Lett. 1976, 37, 232. (37) Zahniser, M.S.; Kaufman, F.; Anderson, J.G. Chem. Phys. Lett. 1976, 37, 226. (38) Nicovich, J.M.; Kreutter, K.D.; Wine, P.H. Int. J. Chem. Kinet. 1990, 22, 399.
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