| OCR Text |
Show Some of the reaction rate expressions were updated to reflect recent results in the literature. For the reaction between HCl and OH radicals , HCl + OH => H20 + Cl ( 7 ) we used R~vishaDkara's rate [lB], k = 2.71 x 107Tl.65exp (0 . 222 kcal/mole) cm3 -mole- 1 -sec- 1 , which gives a description of the non-Arrhenius behavior. This rate is about a factor of two faster than Baulch's rate [19] at 1100 K. The recent laser photolysis/laser-induced fluorescence measurements by Taylor et al. [13] have been used to update the rate parameters for ( 91 ) The updated rate is about two times more rapid at 1100 K than the previous rate given in Reference 4. Russell et al. [B] recently studied the rate of CH2CCl + O2 => CC1HO + HCO ( 105 ) We have employed their measured rate expression which is very similar to the one estimated in Reference 4. Fisher et al. [5] considered site-specific rates of abstraction of H-atoms from chloroethane to explain the presence of C2H3Cl in their flow reactor. We have adopted their rates for the reactions of chloroethane and dichloroethane with radical species. For the rate of the thermal decomposition of HC1, HCl + M H + Cl + M (1 , 2) Reference 4 specified the forward rate and the reverse rate was calculated by thermochemistry. Under the stirred reactor conditions examined here, this leads to a much too rapid rate of recombination of Hand Cl atoms. The rate exceeds gas-kinetic collision rates for temperatures below BOO K. Alternatively, we specified the reverse rate (Reaction 2) and calculated the forward rate from thermochemistry. To specify the reverse rate, we assumed a Cu~ttu2e o~ T- 2 a~ in Wtgner [20]. We chose a rate expression of 7.2 x 10 T- cm -mole- -sec- so that the forward rate (Reaction 1) would agree with Baulch's [19] rate at 2900 K (the lowest temperature he examined). This rate expression gives reasonable recombination rates for temperatures of 300 K and above. Calculations showed significant sensitivity to this rate constant, particularly before the reverse rate was reduced to the above value. Because of the lack of information on this reaction, there is a real need to examine this recombination rate constant experimentally and theoretically . Finally, note that for reactions involving chlorinated species that were not discussed above, their rate expressions were taken directly from Reference 4. Numerical model The oxidation of chlorinated hydrocarbons was examined under conditions of a perfectly-stirred reactor where the reactants, intermediate species and products were assumed to be perfectly mixed and react for a specified residence time, T. The PSR (Perfectly Stirred Reactor) code by Glarborg et. al [21] and CHEMKIN [22] were used to perform the calculations. The temperature of the reactor was specified so -3- |
