A quantum chemical computation and model investigation for autoignition kinetic of a long chain oxygenate: Tri-propylene glycol methyl ether

Abstract

Tri-propylene glycol methyl ether (TPGME) is a promising bio-based oxygenated fuel for advanced engines. The internal H-migration of peroxy (ROO) radicals is a critical factor in the process of TPGME autoignition. In this work, the potential energy surfaces (PESs) of the internal H-migration of ROO radicals as well as alcohol elimination of TPGME were calculated with a high-level DLPNO-CCSD(T)/cc-pVTZ//B3LYP-D3/6–311++G(d,p) method. Rate constants for target reactions were then obtained over a temperature range of 300–1000 K using conventional transition state (CTST) theory. The rate constants for above reactions in the Burke’s model [Combust. Flame. 2015, 16 2(7), 2916–2927] were updated with the calculated results, followed by the modification for important reaction using an analogy strategy, to obtain a revised model. It was found that the feasibility of the H-migration of ROO radicals depended on the transition state ring size and the C-H bond energy of the transferred hydrogen atom, with 1, 5H-migration and 1, 6H-migration played a leading role in the process of TPGME autoignition. Validation against the shock tube (ST), jet stirred reactor (JSR) and collaborative fuel research (CFR) engine measurements from the literature showed that the revised model improved the prediction accuracy. In comparison to n-heptane, the CFR simulation proved that more available hydrogens of 1,5H-migration and 1,6H-migration, as well as higher concentrations and rate of production (ROP) for key low-temperature intermediate species, were contributing factors that stronger low-temperature oxidation activity of TPGME.