Study On The New Branch In Low Temperature Oxidation Of Methanol And Heptane

In order to investigate the interaction between methanol and n-heptane in their low temperature oxidation,and furthermore to improve their mechanism,the mechanis tic study of the reactions of heptyl radicals with methanol and methyl peroxy radical with methanol or hydroxyl methyl radical were studied.The detail mechanism and the accurate rate constants of the reactions have been given in this paper.Theoretical study on the kinetics for the reactions of heptyl radicals with methanol was investigated at BB1K/MG3S level of theory.The geometries and frequencies of all stationary points were calculated at the same level of theory and their energetic parameters have been refined at CBS-QB3 level of theory.The results in potential energy surfaces shown that there are ten channels are confirmed and the hydrogen abstraction reactions are more kinetically favorable in the reaction of heptyl radicals with methanol.The rate constants of H-abstraction channels have been calculated with transition state theory and the Eckart tunneling corrections were included?TST/Eck?.The calculated rate constants have positive temperature dependence and the tunneling effect is only important at low temperature ranges.The reverse reactions of H-atom abstraction from OH in CH₃OH by n-heptyl are predominant in the low temperature region,and this observation can be useful in studies of the behavior of methanol presenting low road octane number of the gasoline.An ab initio and direct dynamic study on the reactions of CH₃OO+CH₃OH and CH₃OO+CH₂OH has been carried out over the temperature range of 300–1500 K.All stationary points were calculated at MP2/Aug-cc-pVTZ level of theory and the energetic parameters were refined at CCSD?T?/Aug-cc-pVTZ level of theory.For the reaction of CH₃OO+CH₃OH,two hydrogen abstraction channels were confirmed.The rate constants of these two channels have been calculated with TST/Eck.The results shown that the Eckart tunneling effect is important over the lower temperature region,and the calculated rate constants agree well with experiment results.For the reaction of CH₃OO+CH₂OH,eight channels were explored on the lowest singlet and triplet surfaces and an excited intermediate was found to be formed on the singlet surface that plays a crucial role in the kinetics.The overall reaction is dominated by a channel proceeding through the formation of excited intermediate on the singlet surface,where CH₃O and OCH₂OH were given through the impulsive dissociation of the excited intermediate,and its rate constant was calculated by multichannel RRKM-TST method.