The reaction of 2,5-dimethylfuran with hydrogen atoms - An experimental and theoretical study

The kinetics of the reaction of hydrogen atoms with 2,5-dimethylfuran (25DMF), a promising liquid transport biofuel, was experimentally studied in a shock tube at temperatures between 970 and 1240 K and pressures of 1.6 and 4.8 bar. The hydrogen atoms were produced by pyrolysis of ethyl iodide and monitored by atom resonance absorption spectrometry. From the hydrogen atom concentration-time profiles, overall rate coefficients for the reaction H + 25DMF →products (R1) were inferred. The results can be expressed by the Arrhenius equation κ₁ = 4.4 × 10^-11 exp(-1180 K/T) cm^-3 s^-1 with an estimated uncertainty of ±30%. A significant pressure dependence was not observed. The results were analyzed in terms of statistical rate theory with molecular and transition state data from quantum chemical calculations. Three different compound methods were used to characterize the potential energy surface: CBS-QB3, CBSAPNO, and G3. It is found that reaction (R1) mainly (>75%) proceeds via an addition-elimination mechanism to yield 2-methylfuran + CH₃. Kinetic parameters for the most important competing channels of the net reaction (R1) were calculated.