Resonance absorption measurements of atom concentrations in reacting gas mixtures. 3. Pyrolysis of methane-d4 behind shock waves

Abstract

Dilute mixtures (10 to 100 ppM) of CD/sub 4/ in argon were pyrolyzed behind reflected shock waves at temperatures of 1780 to 2440 K and total pressures of 2 to 3 atm. Progress of the reaction was followed by analysis for D atoms by using resonance absorption spectroscopy. Rate constants were determined as follows: CD/sub 4/ ..-->.. CD/sub 3/ + D, k/sub 1/ = 1.4 x 10/sup 11/ exp(-81000/RT) s/sup -1/; CD/sub 4/ + Ar ..-->.. CD/sub 3/ + D + Ar, k/sub 1a/ = 2.1 x 10/sup 16/ exp(-84900/RT) mol/sup -1/ cm/sup 3/ s/sup -1/; D + CD/sub 4/ ..-->.. D/sub 2/ + CD/sub 3/,k/sub 2/ = 2.1 x 10/sup 15/exp(-22300/RT) mol/sup -1/ cm/sup 3/ s/sup -1/, where activation energies are in calories. These data have been correlated with similar data by Roth and Just on pyrolysis of CH/sub 4/, with laser schlieren data by Tabayashi and Bauer on pyrolysis of CH/sub 4/ and CD/sub 4/, and with other data on CH/sub 4/ pyrolysis, via RRKM and activated complex theory calculations.