Cyclic ethers are important intermediate products in combustion, in atmospheric oxidation of hydrocarbons, and in the oxidation of biomass derived alcohols. Cyclic ethers are also formed in atmospheric reactions of hydrocarbons, where they have been linked to the formation of the secondary organic aerosol (SOA) in atmospheric chemistry. The cyclic ethers form radicals in combustion and atmospheric oxidation, which can undergo dissociation or react with 3O2 to form peroxy radicals that further react to form reactive oxygenated intermediates. Composite ab initio calculation methods are used to calculate thermochemistry of the five member ring cyclic ether, tetrahydrofuran (THF) and its corresponding radicals. Elementary reaction pathways for unimolecular decomposition and for oxidation of the cyclic ether radicals by addition reaction of first and second 3O2 are analyzed. The peroxy radical can undergo dissociation back to reactant, isomerize via intramolecular hydrogen transfer, or undergo ring opening and subsequent dissociation reactions with some leading to chain branching. The radical intermediates can also undergo H atom elimination reactions to form olefin cyclic ethers. Thermochemical (δHf°, ΔS0Cp (298 < T < 1500 K)) and kinetic parameters are developed for the 2-oxolanyl and 3-oxolanyl radicals and their elementary reaction paths in the first and the second 3O2 oxidation steps. A chemical activation kinetic analysis using QRRK for k(E) and master equation analysis for falloff is used to calculate rate constants as a function of pressure and temperature. A reaction mechanism is used to illustrate products versus time and temperature of the isolated ether systems.
|Original language||English (US)|
|Title of host publication||10th U.S. National Combustion Meeting|
|Publisher||Eastern States Section of the Combustion Institute|
|State||Published - Jan 1 2017|