Low-temperature oxidation of propene in a supercritical jet-stirred reactor up to 100 atm

In this work, the propene oxidation is experimentally studied by using a supercritical pressure jet-stirred reactor (SP-JSR) at 10 and 100 atm, over a temperature range of 600-950 K, at fuel lean and rich conditions. A negative temperature coefficient (NTC) region is found under 100 atm at fuel rich condition, which doesn’t exist in atmospheric pressure condition. Furthermore, OH addition to propene is found to be the dominant pathway under 100 atm. However, the following O₂ addition reactions are not complete in previous propene models. Thus, theoretical calculations are performed to determine the rate constants of two hydroxypropyl radicals related reactions. The updated model shows improvement but still fails to capture the NTC behavior. The possible reasons might be the uncertainties of the initiation reactions and the missing pathways of important intermediates under 100 atm. Reaction pathway analysis is performed under 10 atm, 925 K and 100 atm 725 K. It is found that under 100 atm, the main consumption pathway is OH addition to form hydroxypropyl radicals and they will go through O₂ addition to give ROO radicals. The ROO radical is not stable and will decompose to acetaldehyde and formaldehyde and OH, also, it will form three-membered ring species. However, under 10 atm, H-abstraction of propene to form allyl radical dominants propene oxidation.