Investigation of the ³CH₂ + O₂ reaction in shock waves

Abstract

The reaction of 3CH2 with O2 was investigated in incident shock waves for pressures near 1 bar and temperatures from 1000 to about 1800 K. 3CH2 source was diazomethane. The concentration time curves of CO and CO2 were obtained from infrared emission, the OH profiles by laser absorption measurements. Data for O and H atom formation in this reaction were reported recently. – The measurements show that about a quarter of the reaction proceeds by forming radicals directly. Three quarters of the reaction form stable products only. Main reaction product is CO with a CO to CO2 ratio near 4:1. Direct formation of OH does not exceed a few percent. A reaction channel distribution is given. – Rate constants for the total reaction 3CH2 + O2 obtained by computer simulation of the product profiles in the temperature range mentioned are below the data extrapolated from measurements performed by Vinckier et al. and Bley et al. in the temperature range around room temperature. A rate expression fitting the measured date over the whole temperature range is reported.

Direct Dynamics Simulations of the 3CH2 + 3O2 Reaction at High Temperature

“…The CO/CO 2 ratio without and with correcting for product dissociation is 4.3:1 and 5.3:1, respectively. This agrees quite well with the ratio of 4:1 obtained by Dombrowsky and Wagner at high temperatures . Their study further showed that the formation of OH radical does not exceed a few percent.…”

“…This agrees quite well with the ratio of 4:1 obtained by Dombrowsky and Wagner at high temperatures. 11 Their study further showed that the formation of OH radical does not exceed a few percent. But, the product decomposition analysis shows that 37% of H 2 O dissociates into OH + H adding up significant contribution to the CO + OH + H product channel, thereby increasing the OH yield.…”

“…Table 4 compares the product yields obtained from 1000 K simulations with 300 K simulations. First, we compare the simulation results with the experimental results of Dombrowsky et al 11,12 Dombrowsky and Wagner 11 showed that the reaction channels producing the OH radical are of minor importance at high temperatures and should not have a profound influence on O and H atom profiles. However, the product decomposition analysis in the present study shows that almost 37% of H 2 O formed in the CO + H 2 O reaction channel dissociate into OH + H, thereby increasing the OH yield and influencing the H atom profiles.…”

“…10 The above-mentioned studies are for 300 K room temperature. Dombrowsky and Wagner investigated the reaction of 3 CH 2 + 3 O 2 in shock waves at high temperatures ranging from 1000 to 1800 K. 11 Their study showed that about three-quarters of the reaction proceeds by formation of stable products and onequarter leads to radical products. The major product was CO with a CO:CO 2 ratio of 4:1, and formation of the OH radical was a small percentage.…”

“…Dombrowsky and Wagner investigated the reaction of 3 CH 2 + 3 O 2 in shock waves at high temperatures ranging from 1000 to 1800 K . Their study showed that about three-quarters of the reaction proceeds by formation of stable products and one-quarter leads to radical products.…”