Studies of high-pressure n-butane oxidation with CO2 dilution up to 100 atm using a supercritical-pressure jet-stirred reactor

A novel supercritical-pressure jet stirred reactor (SP-JSR) is developed to operate up to 200 atm. The SP-JSR provides a unique platform to conduct kinetic studies at low and intermediate temperatures at extreme pressures under uniform temperature distribution and a short flow residence time. n-Butane oxidations with varying levels of CO2 dilutions at pressures of 10 and 100 atm and over a temperature range of 500-900 K were conducted using the SP-JSR. The experiment showed that at 100 atm, a weak NTC behavior is observed and the intermediate temperature oxidation is shifted to lower temperatures. Furthermore, the results showed that CO2 addition at supercritical conditions slows down the fuel oxidation at intermediate temperature while has little effect on the low temperature oxidation. The Healy model under-predicts the NTC behavior and shows little sensitivity of the effect of CO2 addition on the n-butane oxidation. Reaction pathway and sensitivity analyses exhibit that both the low and intermediate temperature chemistries are controlled by RO2 consumption pathways. In addition, the reactions of CH3CO (+ M) and CH3CO + O2 become important at 100 atm. The results also revealed that fuel oxidation kinetics is insensitive to the third body effect of CO2. The kinetic effect of supercritical CO2 addition may come from the reactions involving H2O2, CO, CH2O, and CH3CHO, especially for the reactions of CO2 + H and CO2 + OH.