Exploring the Chemical Kinetics of the First Oxygen Addition to Di-n-Propyl Ether Radicals at Low Temperatures

Linear ethers are promising biomass fuels with high volume energy density and high cetane number that may be used directly as alternative fuels or fuel additives in internal combustion engines. In this work, the first O₂ addition reaction of the di-n-propyl ether radical was investigated using high-level quantum chemical calculations combined with the Rice-Ramsperger-Kassel-Marcus theory to solve the master equation. The potential energy surfaces of di-n-propyl ether radicals (C₆H₁₃O) with O₂ were constructed at the QCISD(T)/CBS//M062X/6-311++G(d, p) level, and the rate constants were calculated for the pressure range of 0.1-100 atm and the temperature range of 300-1500 K and fitted by a modified Arrhenius formula. The calculations show that the consumption of di-n-propyl ether peroxyl radicals (C₆H₁₃O₃) via the five-membered ring or six-membered ring transition-state reaction channel is most favorable. In addition, the low-temperature oxidation experiments of di-n-propyl ether were validated based on the calculations of the current work, and the results showed that the calculations were a good predictor of the experimental results.