Unraveling the high reactivity of 3-methyltetrahydrofuran over 2-methyltetrahydrofuran through kinetic modeling and experiments

The progress in catalysis research has recently led to new conversion pathways of cellulosic biomass to a range of tetrahydrofurans, which are potentially viable as biofuels. However, combustion behavior of these tetrahydrofurans is not well understood. Considering this as the main focus, the present study reports for the first time the formulation of a detailed chemical kinetic model of 3-methyltetrahydrofuran (3-MTHF). The developed model includes both its low- and high-temperature chemistry and is able to explain the reason for higher reactivity of 3-MTHF than 2-methyltetrahydrofuran (2-MTHF). In order to assess the prediction capability of the proposed model, ignition delay measurements of 3-MTHF were performed in two different combustion reactors, rapid compression machine and shock tube. The ignition delay times were measured for 3-MTHF/air mixtures spanning a wide range of temperatures from 615 K to 1256 K, at pressures of 10 bar, 20 bar, and 40 bar, and varying equivalence ratio of 0.5, 1.0, and 2.0. The proposed model compares well against new and already existing experimental data. A detailed chemical analysis of the auto-ignition of 3-MTHF reveals that the presence of two secondary α-carbon centers and hence four α-C-H bonds leads to its substantially higher reactivity in comparison to its structural isomer 2-MTHF, which possesses one secondary α- and one tertiary α-carbon center.