Experimental and modeling study of the thermal decomposition of C3-C5 ethyl esters behind reflected shock waves

The thermal decomposition of three ethyl esters, ethyl formate (C3H6O2), ethyl acetate (C4H8O2), and ethyl propanoate (C5H10O2), was studied behind reflected shock waves using laser absorption to measure concentration time-histories of H2O, CO2, and CO. Experimental conditions covered temperatures of 1301-1636 K, pressures of 1.48-1.72 atm, and reactant concentrations of 2000 ppm in argon. Recently developed mid-infrared laser diagnostics for H2O (2.5 μm), CO2 (4.3 μm), and CO (4.6 μm) provide orders-of-magnitude greater detectivity compared to previous near-infrared absorption sensors. The experimental results have highlighted significant differences among these three ethyl esters: negligible CO2 production during ethyl formate pyrolysis, quite slow CO formation rate during ethyl acetate pyrolysis, and nearly equal formation rate of H2O, CO2, and CO during ethyl propanoate pyrolysis. Detailed kinetic modeling was performed to understand the destruction pathways of these three ethyl esters with different alkyl chain lengths. Rate of production and sensitivity analyses were also carried out to interpret the experimental results and to identify the key reactions affecting experimental results.