Soot precursors in farnesane and n-dodecane decomposition: A computational approach

[Display omitted] •Identification and quantification of soot precursors by quantum chemistry approach.•Sub-mechanism containing hydrogen abstraction and beta-scission reactions.•Kinetic parameters for several alkane elementary reactions.•Farnesane produces ten times lower soot precursors than n-dodecane. The worldwide increase concern about the use of fossil fuels is causing a running for the development of green fuels, trying to slow down the emissions of soot and greenhouse gases. Recent studies are pointing up that branched carbon chain structures of alkanes, terpenoids, and sesquiterpenes produce less soot during combustion, they have been employed as an additive in diesel/kerosene engines. In this work, a decomposition sub-mechanism of farnesane and n-dodecane fuels was studied, using the calculated Arrhenius parameters for several hydrogen abstractions and β-scission elementary reactions to compare the preceding species of the soot precursors. The calculations were carried out using density functional theory to obtain the thermochemical properties of all molecules and transition state theory to calculate the thermal rate coefficients. The results showed the importance of the thermochemical analysis in choosing the appropriate temperature range for the selected reactions, to obtain a qualitatively appropriate set of kinetic parameters. The molar fraction comparison resulting from the sub-mechanism of the two fuels revealed that farnesane yields a smaller amount of species necessary to produce soot precursors due to the position of the branched carbons. The methodology used here allows the construction of additive mechanisms and can be used to aid the design of new fuels that could be more efficient and/or less polluting. By investigating, for example, the first steps of a fuel decomposition in a reduced mechanism, avoiding the complexity of a complete mechanism, while also generating fairly accurate kinetic parameters for elementary reactions.