Direct Measurement of High-Temperature Rate Constants of the Thermal Decomposition of Dimethoxymethane, a Shock Tube and Modeling Study

Shock-tube experiments have been performed to investigate the thermal decomposition of the oxygenated hydrocarbon dimethoxymethane (DMM; CH3OCH2OCH3). The primary initial reaction channels of DMM decomposition are considered to be the two bond fissions: CH3OCH2OCH3 -> CH3O + CH2OCH3 (1) and CH3OCH2OCH3 -> CH3 + OCH2OCH3 (2). In the present work, two shock-tube facilities and three different detection techniques have been combined: Behind reflected shock waves, we have carried out time-resolved measurements of (i) the formation of H atoms using the highly sensitive H-ARAS (Atomic Resonance Absorption Spectrometry) technique and (ii) the depletion of the DMM reactant by high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS). In addition, (iii) the temperature-dependent composition of stable reaction products was measured in single-pulse shock-tube experiments via gas chromatography (GC/MS). The experiments span a temperature range of 1100-1430 K, a pressure range of 1.2-2.5 bar, and initial reactant mole fractions from 0.5 ppm (for H-ARAS experiments) up to 10 000 ppm (for HRR-TOF-MS experiments). Experimental rate constants k(total), k(total) = k(1) + k(2), obtained from these three completely different methods were in excellent agreement among each other, i.e., deviations are within +/- 30-40%, and they can be well represented by the Arrhenius expression k(total)( T) = 10(13.28 +/- 0.27) exp(-247.90 +/- 6.36 kJ mol(-1)/ RT) s(-1) (valid over the 1100-1400 K temperature and the 1.2-2.5 bar pressure range). By replacing the respective ktotal values used in a recently published DMM chemical kinetics combustion mechanism (Vermeire et al. Combust. Flame 2018, 190, 270-283), it was also possible to successfully reproduce measured product distributions.