Theoretical Studies of the Hydrogen Abstraction from Poly(oxymethylene) Dimethyl Ethers by O₂ in Relation with Cetane Number Data

Abstract

Poly(oxymethylene) dimethyl ethers (PODMEn, n = 2–6) are novel oxygenated compounds that can be used as promising candidates for new-generation fuels because of their excellent combustion performance. The oxidation of PODMEn (n = 2–6) is essential for the understanding of the combustion process. It is necessary to study the relationship between kinetic parameters and cetane number (CN) of PODMEn (n = 2–6). In order to predict initiation step rate constants for the oxidation of PODMEn (n = 2–6), quantum mechanical calculations are performed using M06-2X/6-311G(d,p) and B3LYP/6-311G(d,p) methods. Structural, energetic, thermodynamics, and kinetics of the automatic ignition process are assessed. The kinetic model based on the conventional transition state theory is used to calculate the initiation step reaction rate constants at 1000 K. In both M06-2X/6-311G(d,p) and B3LYP/6-311G(d,p) methods, the calculated rate constants of the hydrogen abstraction process have an excellent correlation with the experimental CN of PODMEn (n = 2–6). Our methodology presented here can be used to simulate chemical kinetics for other fuel additives.

Large Computational Survey of Intrinsic Reactivity of Aromatic Carbon Atoms with Respect to a Model Aldehyde Oxidase

“…These much lower barriers (up to 17.5 kcal/mol lower) are not entirely surprising. The M06-2X functional has been observed to yield much lower reaction barriers compared to B3LYP in some reaction types, , although B3LYP produced much lower reaction barriers than M06-2X in other reaction types. , Our calculations performed with B3LYP/LACVP+** show a much higher barrier than those obtained with M06-2X/LACVP+**, in a better quantitative agreement with Alfaro and Jones’ B3LYP/cc-aug-pVDZ calculations (see Figure ).…”

A Mini-Review on the Advances in the Kinetic Understanding of the Combustion of Linear and Cyclic Oxymethylene Ethers

“…This comparison demonstrates that all of the OME n with n > 1 qualify with the requirements, in terms of cetane number of diesel fuels in the European Union, but that OME n with n > 4 could pose problems, in terms of melting point. An attempt to correlate the CN of OME n with the global reaction rate constants of the bimolecular initiation reaction of OME n with O 2 calculated at 1000 K using M06-2X/6-311G­(d,p) and B3LYP/6-311G­(d,p) methods was performed in ref . All OME n have inferior lower heating values (LHVs) than expected from a diesel fuel, demonstrating that they cannot be used pure in the current state of regulations.…”